Achilles tendinopathy

INTRODUCTION — 

Pain of the Achilles tendon commonly affects both competitive and recreational athletes as well as the sedentary patient. The largest tendon in the body, the Achilles tendon, endures strain and risks rupture from running, jumping, and sudden acceleration or deceleration. Overuse, vascular diseases, neuropathy, and rheumatologic diseases may cause tendon degeneration. The hallmarks of Achilles tendon problems seem to be damaged, weak, and inelastic tissue.

This topic review will discuss the mechanism, diagnosis, and management of Achilles tendinopathy. Achilles tendon rupture and general discussions of tendinopathy pathogenesis and management are provided separately. (See "Achilles tendon rupture" and "Tendinopathy: Overview of management" and "Tendinopathy: Overview of pathophysiology, epidemiology, and presentation".)

TERMINOLOGY — 

"Tendonitis," "tendinosis," "tendinopathy," "paratendinitis," "enthesopathy," and "insertional tendonitis" are among the terms used to characterize acute or chronic tendon pain. The common term "tendonitis" is confusing because inflammation is not often seen on histopathology. Throughout this review, we will use the term "tendinopathy" to refer to acute and chronic pain associated with an Achilles tendon injury not associated with tendon tear or rupture. (See "Tendinopathy: Overview of pathophysiology, epidemiology, and presentation", section on 'Pathology and terminology'.)

EPIDEMIOLOGY AND RISK FACTORS — 

Achilles tendinopathy affects competitive and recreational athletes as well as people who are not active [1]. Observational data suggest that competitive athletes have a lifetime incidence of Achilles tendinopathy of 24 percent, with 18 percent sustained by athletes younger than 45 years [2]. Achilles tendinopathy in recreational runners, although less likely to involve rupture, accounts for 6 to 17 percent of all running injuries [3]. Military recruits develop tendinopathy at a rate of 6.8 percent [4].

Although evidence is limited, a number of conditions and environmental exposures may be associated with an increased risk of developing Achilles tendinopathy (table 1) [5]. Cold-weather training is associated with higher rates of tendon pain generally and Achilles tendinopathy specifically [4,5]. Additional risk factors associated with Achilles tendinopathy include the following [5-9]:

●Prior history of tendinopathy

●Poor running mechanics (eg, excessive supination, inadequate dorsiflexion)

●Worn-out or inappropriate footwear

●Weakness in foot and ankle plantarflexion

●Leg-length discrepancy

●Increased age

●Male sex

●Being overweight

Some clinicians believe that certain foot structures are associated with an increased risk for Achilles tendinopathy, but evidence is inconsistent and consists largely of small, observational cohort studies [10-12]. A high-arched foot (pes cavus) and hindfoot (calcaneal) varus appear to have the strongest association with Achilles tendinopathy and other hindfoot conditions [13,14]. In a prospective study of 166 elite and recreational runners with four-year follow-up, 24 percent developed Achilles tendinopathy, varus hindfoot was present in 87.5 percent of foot and leg injuries overall and cavus arch in 71.4 percent [14]. Other observational studies have reported that varus hindfoot and diminished ankle dorsiflexion are associated with Achilles tendinopathy [13].

Fluoroquinolone antibiotics are rarely associated with Achilles tendinopathy (or tendon rupture) [5,15]. However, older adults may be at increased risk. In a retrospective case-control study of data taken from a national health database, patients aged 60 or over taking a fluoroquinolone had an increased relative risk (RR) of Achilles tendon disorders ("tendinitis" in 95 percent of cases) compared with those not taking the medication (RR 1.9, 95% CI 1.3-2.6) [16]. Concurrent use of glucocorticoids and fluoroquinolones further increased the risk, but case numbers were small. (See "Fluoroquinolones", section on 'Tendinopathy' and 'Measures for patients on fluoroquinolones' below.)

Oral and locally injected glucocorticoids appear to increase the risk of acute Achilles tendon injury, but their role in the development of Achilles tendinopathy is unclear. The appropriate use and risks associated with glucocorticoid therapy for tendinopathy are discussed separately. (See "Tendinopathy: Overview of management", section on 'Glucocorticoids'.)

In women, hypertension is associated with Achilles tendinopathy [8]. Other diseases associated with tendinopathy include psoriasis and ankylosing spondylosis [17]. However, heel pain is rarely the presenting symptom in patients with these systemic diseases [18].

CLINICAL ANATOMY — 

The soleus and gastrocnemius muscles converge to form the Achilles tendon, which inserts posteriorly on the calcaneus (figure 1 and figure 2 and figure 3 and figure 4). Contraction of these muscles, along with the actions of the tibialis posterior (picture 1) and peroneus (fibularis) longus and brevis (picture 2 and picture 3), causes the foot to plantarflex. The subcutaneous and subtendinous (or retrocalcaneal) calcaneal bursae cushion the insertion area anteriorly and posteriorly. Most pain and tendon ruptures occur where the blood supply of the gastrocnemius-soleus muscle complex is poorest, 2 to 6 cm above the insertion point. A peritendinous sheath of connective tissue allows the tendon to slide relative to surrounding tissue.

MECHANISM OF INJURY AND PATHOPHYSIOLOGY — 

Acute Achilles tendon pain generally develops when athletes abruptly increase their activity (eg, runners who start training for a marathon). Chronic tendon pain (>3 months) may result from sustained stress, poor running mechanics (eg, forefoot supination, increased hindfoot inversion [ie, varus]), anatomic problems (eg, tight gastrocnemius, restricted ankle motion), or improper footwear [13,19]. Some experts claim a role for excessive pronation in Achilles tendinopathy among runners, but others dispute this.

Ideally, during running gait, foot-strike occurs centrally at the midfoot and forces are transferred directly forward to the metatarsals. Over-pronation or under-pronation (ie, supination) causes the foot to land on either side, including the outer edges of the calcaneus. With over-pronation, impact on the foot is too medial, while under-pronation causes impact to be too lateral. During walking gait, over-pronation causes the foot to roll medially, while under-pronation causes the foot to roll laterally.

The Achilles tendon insertion onto the calcaneus is medial to the axis of the subtalar joint, making the calf muscles the most powerful supinators of the subtalar joint. When there is chronic, excessive foot pronation superimposed on this structural relationship, greater cumulative strain is placed on the Achilles tendon [20]. Pronation causes internal tibial rotation, which tends to pull the Achilles tendon medially. Studies using slow-motion, high-speed cinematography demonstrate that pronation produces a "whipping action or bowstring effect" in the Achilles tendon. This whipping action, when exaggerated, is thought to contribute to tendinopathy.

Excessive loading of the tendon during vigorous training activities is regarded as a significant pathological stimulus, although Achilles tendinopathy is not always associated with significant physical activity. Recurrent microtrauma from vigorous activity and/or poor gait mechanics contributes to degeneration of the Achilles tendon and may be an important factor in the development of tendinopathy [19,21]. The relative hypovascularity of the tendon 2 to 6 cm from its insertion on the calcaneus may prevent adequate healing. Although inflammation is often not seen on histopathology, clinical signs similar to those seen with inflammation (such as swelling, warmth, and pain) may occur. Damaged tendons become calcified, thickened, inelastic, and fibrotic. Abnormal neovascularization of tissue may be seen on ultrasound. Aging and vascular disease decrease collagen density, break collagen cross-links, and reduce the elasticity of the tendon sheath and tendon itself. The pathophysiology of overuse (chronic) tendinopathy is discussed in greater detail separately. (See "Tendinopathy: Overview of pathophysiology, epidemiology, and presentation".)

CLINICAL PRESENTATION — 

Patients with Achilles tendinopathy typically complain of pain or stiffness 2 to 6 cm above (cephalad or proximal to) the posterior calcaneus. A significant minority of patients complain of pain at the tendon insertion. Patients are likely to be casual or competitive athletes who have increased their training regimen beyond the tendon's ability to heal the microtrauma from repetitive stress, or who have been training rigorously for a long time. A history of excessive supination, increased speed work or hill training, or improper or worn-out footwear may be found.

Achilles tendinitis (acute inflammation) can cause pain and stiffness along the Achilles tendon, especially with the first steps taken in the morning. The pain is worse with activity and may be relieved by a period of rest.

PHYSICAL EXAMINATION

General evaluation — Examination of the Achilles tendon is usually straightforward because the tendon is easily identified and palpated. However, potential pitfalls exist (table 2). Of note, a sizable minority of patients with complete tendon rupture are able to ambulate. (See "Achilles tendon rupture".)

●Inspection – Examine the patient's footwear, looking for signs of excessive breakdown (eg, disproportionate wear on the inner or outer edge) or other evidence of poor running mechanics. Examine the architecture of the patient's foot. The presence of flat feet (pes planus), heel malalignment, high arches (pes cavus), or leg-length discrepancy can contribute to poor running mechanics [22].

Patients should be examined lying prone with their feet hanging off the end of the examination table. Inspect the region of the Achilles tendon for bruising (blood tracking beneath the malleolus suggests fracture, sprain, or tendon rupture), swelling, and foot misalignment. Assess patients for signs of peripheral artery disease, such as decreased pulsations, decreased capillary refill in the heel or toes, loss of hair, increased skin pigmentation, or edema. (See "Overview of lower extremity peripheral artery disease".)

●Palpation – Palpate the Achilles tendon for tenderness, thickening, or a defect, recognizing that edema or a hematoma may mask such a defect. Palpation has a sensitivity of approximately 73 percent and a specificity of 89 percent in detecting a partial tendon tear [23]. Palpation by pinching the tendon from the medial and lateral borders is usually more sensitive for eliciting tenderness, as the large (Kager) fat pad deep to the tendon can absorb and abate pressure from posterior palpation. Comparison to the unaffected side is useful.

Patients with tendinopathy typically have localized tenderness 2 to 6 cm proximal to the insertion of the tendon (picture 4). By comparison, tenderness around the insertion point near the heel suggests either subcutaneous calcaneal bursitis or enthesopathy (pathology of tendon at its insertion) [24]. Warmth and tenderness localized to the soft tissue anterior to the area where the Achilles inserts suggest subcutaneous bursitis, although this condition is uncommon. Focal tenderness of the tendon itself in the area where it inserts suggests enthesopathy.

The tendon should be palpated as the patient dorsiflexes and plantarflexes the foot, as well as when the ankle is stationary in a neutral position. The presence of focal tendon swelling, nodularity, or crepitus with motion suggests tendinopathy.

Isolating the subtendinous bursa (ie, retrocalcaneal bursa) and palpating it for tenderness may identify bursitis. We perform this examination as follows: grasp the Achilles tendon with the fingers of one hand and move the tendon side to side. Bursitis should not cause pain when only the tendon is palpated. Next, with the index finger on the opposite hand, apply gentle pressure deep to the tendon. Continue to grasp the tendon with the other hand to be certain you are palpating the bursa and not the tendon. Local warmth and tenderness deep to the tendon with light pressure suggest that the subtendinous (or retrocalcaneal) bursa is inflamed.

●Gait assessment – Whenever possible, assess the patient's gait or running stride, looking for abnormalities or asymmetry. With running gait, look specifically for supinated foot strike, forefoot strike (particularly where the heel fails to make ground contact), and excessive horizontal motion at the heel. (See "Clinical assessment of walking and running gait".)

Special tests — The calf squeeze (or Thompson) test provides an accurate means for detecting complete Achilles tendon rupture (picture 5 and movie 1). This test and others for assessing tendon tear are reviewed separately. (See "Achilles tendon rupture", section on 'Physical examination'.)

DIAGNOSTIC IMAGING — 

Achilles tendinopathy (without rupture) is a clinical diagnosis. Imaging is generally not necessary except to rule out other conditions, such as a stress fracture or tendon rupture.

Plain radiographs are generally unhelpful in the assessment of Achilles tendon pathology but may reveal a heel spur or bony bump (called a Haglund's deformity (picture 6) or "pump bump") consistent with both tendinopathy and calcaneal bursitis.

Ultrasound imaging is increasingly used to assess tendon appearance and function [25]. Ultrasound may reveal normal tendon, tendon thickening (image 1), or signs of more significant tendon pathology, such as neovessels (image 2), hypoechogenicity, disordered fibers, tissue gaps (partial tears), and fluid (image 2 and movie 2) [10,25]. In addition to midportion Achilles tendinopathy, ultrasound can reveal enthesopathy or avulsion injuries at the distal portion of the tendon (image 3). Ultrasound can also help to distinguish between Achilles tendon injury and other pathology (image 4).

While some propose that ultrasound examination be used to identify abnormalities that may increase the risk for subsequent Achilles injury, evidence suggests ultrasound has limited utility for widespread screening [26,27]. In a systematic review and meta-analysis of 16 studies of asymptomatic, young adult athletes, including 810 Achilles tendon assessments, abnormal ultrasound findings predicted future symptoms in only 27 percent of participants [26]. Conversely, the negative predictive value of a normal ultrasound was high, as 92 percent of athletes without an abnormal finding did not develop symptoms of Achilles tendinopathy. This finding was replicated in a prospective observational study of 473 United States collegiate athletes [27]. In specific cases (eg, athlete with a history of Achilles injury), there may be a benefit to identifying athletes with asymptomatic abnormalities of the Achilles tendon.

With acute tendinopathy, magnetic resonance imaging (MRI) may demonstrate an increased T2-weighted signal in the tendon (image 5) or an increased tendon diameter [11]. In addition, MRI may reveal alternative explanations for patient symptoms, such as enlarged calcaneal bursae [25].

Neither ultrasound nor MRI findings appear to correlate closely with clinically significant chronic Achilles tendinopathy. In one small prospective study, ultrasound detected abnormal morphology in 37 of 57 symptomatic Achilles tendons, while MRI detected abnormalities in 19 of 34 (MRI was performed in a subset of 25 consecutive patients) [12]. Better baseline MRI appearance was associated with a successful return to sport and symptomatic benefit after 12 months, but baseline ultrasound findings were not. Further study of these diagnostic tests is needed to determine their appropriate role in the management of Achilles tendinopathy.

ADDITIONAL ULTRASOUND RESOURCES — 

Instructional videos demonstrating proper performance of the ultrasound examination of the ankle, including the Achilles tendon, and related pathology can be found at the website of the American Medical Society for Sports Medicine: sports US ankle-foot pathology. Registration must be completed to access these videos, but no fee is required.

DIAGNOSIS — 

Achilles tendinopathy is generally a clinical diagnosis established by history and examination findings, although clinicians skilled with ultrasound commonly seek corroborating evidence with bedside imaging. Patients are likely to be casual or competitive athletes who have recently increased their training intensity. They typically complain of pain or stiffness 2 to 6 cm above the posterior calcaneus that often increases with activity and diminishes with rest. Focal tenderness is present at this location (picture 4). Examination typically reveals increased tendon thickness and possibly a nodule, warmth, or crepitation that is not present in the unaffected contralateral tendon. Ultrasound may reveal tendon thickening (image 1), or signs of more significant pathology, such as neovessels, hypoechogenicity, disordered fibers, tissue gaps, and fluid.

DIFFERENTIAL DIAGNOSIS — 

The differential diagnosis of heel and hindfoot pain is extensive and is discussed in detail separately. (See "Hindfoot pain in adults: Evaluation and diagnosis of common causes".)

Pain arising from the region between the posterior calcaneus and the gastrocnemius-soleus muscle complex may be caused by any of several conditions (table 3). Below, diagnoses commonly confused with Achilles tendon injury are reviewed briefly.

●Retrocalcaneal bursitis – Retrocalcaneal subtendinous bursitis typically occurs in middle-aged or older adult patients (figure 4). Patients may complain of pain where the back of a hard shoe, heel cup, or strap rubs against the heel at the Achilles tendon insertion point. Sports in which athletes wear hard-backed footwear or repeatedly strike their heels against barriers (eg, indoor soccer, hockey) may cause bursitis.

The location of tenderness helps to distinguish bursitis from tendinopathy. With bursitis, neither palpation of the Achilles tendon nor holding it between your thumb and fingers and moving it side to side should elicit pain. Conversely, local warmth and tenderness deep to the tendon with light pressure suggests that the retrocalcaneal bursa is inflamed. Be sure to squeeze the soft tissue behind the Achilles tendon and just above the superior border of the calcaneus. Bursitis generally resolves with basic measures (eg, heel lifts or posterior padding, avoiding bothersome footwear, rest, and pain medication). (See "Hindfoot pain in adults: Evaluation and diagnosis of common causes", section on 'Achilles tendon insertion and Haglund deformity'.)

●Subcutaneous calcaneal bursitis – The subcutaneous calcaneal bursa lies superficial to the Achilles tendon at its insertion on the calcaneus and is subject to becoming inflamed with overuse or direct trauma (figure 4). The swelling associated with this bursitis is sometimes called a "pump bump" due to its association with hard-backed, ill-fitting pump style shoes. Examination reveals swelling and focal tenderness superficial to the tendon insertion, while the tendon itself is nontender. (See "Hindfoot pain in adults: Evaluation and diagnosis of common causes", section on 'Achilles tendon insertion and Haglund deformity'.)

●Calcaneal apophysitis – An apophysis is a growth plate that does not contribute to the linear growth of the bone. The calcaneal apophysis, located on the posterior inferior aspect of the calcaneus, is the growth plate at the insertion of the Achilles tendon. The calcaneal apophysis displays increased metabolic activity during periods of rapid growth, which can place it at risk for overuse injury.

Calcaneal apophysitis (ie, Sever disease) is an overuse injury common in young athletes aged 8 to 15 years, particularly those active in football (ie, soccer), basketball, gymnastics, or running. Patients complain of activity-related pain of insidious onset in the posterior aspect of the heel, which may be unilateral or bilateral. Tenderness is localized to the calcaneal apophysis, usually 1 to 2 cm distal to the Achilles tendon insertion. Symptoms generally resolve within three to six weeks with conservative treatment. (See "Heel pain in the active child or skeletally immature adolescent: Overview of causes", section on 'Calcaneal apophysitis (Sever disease)'.)

●Achilles tendon enthesopathy – Heel pain may stem from an injury or chronic strain at the Achilles tendon insertion, called an enthesopathy (figure 4). This occurs most often in distance runners and athletes involved in running and jumping sports. Examination findings consistent with the diagnosis include local warmth, erythema, swelling, increased tendon thickness, and focal tenderness of the tendon at or near its insertion. Chronic inflammation at the site of the Achilles tendon insertion can cause the development of a bony prominence called a Haglund deformity (picture 6). (See "Hindfoot pain in adults: Evaluation and diagnosis of common causes", section on 'Achilles tendon insertion and Haglund deformity'.)

●Chronic exertional compartment syndrome (CECS) – CECS typically affects young endurance athletes, especially those who run extensively. Like acute compartment syndrome, it is thought to result from increased pressure within a skeletal muscle compartment, usually in the lower leg (figure 5). Runners with CECS typically describe gradually increasing lower leg pain that develops shortly after the start of exercise and resolves soon (within 10 to 20 minutes) after the activity stops. Pain is often described as cramping, squeezing, tightness, or aching. Examination at rest may be unremarkable. (See "Chronic exertional compartment syndrome".)

INDICATIONS FOR REFERRAL — 

Chronic tendinopathy that fails to improve with three to six months of conservative treatment may benefit from consultation with a specialized runners' clinic, sports physician, physical medicine and rehabilitation specialist, physical therapist, or orthopedic surgeon [28].

TREATMENT

Acute tendinopathy — Treatment of acute Achilles tendinopathy generally consists of the following:

●Avoid aggravating activities.

●Apply ice when symptomatic.

●Take a short course (7 to 10 days) of nonsteroidal antiinflammatory drugs (NSAIDs).

●Support the Achilles with a heel lift (approximately 12-mm rise) and with elastic bandage or taping (picture 7) as needed.

The goal of therapy is to relieve symptoms and enable a return to activity. Although the approach described here appears reasonable, there is little high-quality evidence to support it. (See "Initial management of soft tissue musculoskeletal injuries".)

A systematic review of treatments for "Achilles tendinitis" published in 2001 identified three small controlled trials comparing oral NSAIDs with placebo [29]. Although there is no compelling evidence that NSAIDs enable patients to return to full activity sooner or improve outcomes [30], these drugs are a reasonable choice for short-term pain relief in patients with acute Achilles tendinopathy. The role of oral and topical NSAIDs in the treatment of tendinopathy is reviewed separately. (See "Tendinopathy: Overview of management", section on 'Anti-inflammatory medications'.)

A subsequent systematic review of studies looking at the effect of various injections, including glucocorticoids, for the treatment of Achilles tendinopathy found that the studies were of low quality overall, but the results suggest little (if any) benefit from such therapy [31]. This conclusion is consistent with studies of glucocorticoid injection for other tendinopathies. In addition, there are case reports of Achilles tendon rupture after glucocorticoid injection in patients with chronic tendinopathy [32]. (See "Tendinopathy: Overview of management", section on 'Glucocorticoids'.)

Once acute healing has begun, most patients begin some form of rehabilitation. Basic therapy regimens, including such interventions as physical therapy, deep-friction tissue release, and ultrasound, may reduce symptoms over several weeks [33]. Patients should perform an adequate dynamic warm-up before and stretch following inciting activities, once these are resumed. Rehabilitation for chronic Achilles tendinopathy and prevention strategies are discussed below. (See 'Chronic tendinopathy' below and 'Prevention' below.)

Small randomized trials have found no benefit from low-dose heparin injections or heel pads, but heel pads may reduce pain from calcaneal bursitis [29]. Heel lifts are thought to reduce the load placed on the tendon and are commonly used as an adjunct therapy. (See 'Shoe-based interventions' below.)

Chronic tendinopathy — Chronic Achilles tendinopathy exists when pain persists beyond three months. In addition to the basic interventions for acute exacerbations described above, the treatment of chronic midportion Achilles tendon pain should include a rehabilitation program that emphasizes resistance exercises using heavy loads. While methodologic limitations are common in studies of Achilles tendinopathy treatment, rehabilitation using resistance exercises is the best supported approach [34]. A general discussion of treatments for tendinopathy is provided separately. (See "Tendinopathy: Overview of management".)

Rehabilitation using resistance exercise — We suggest that patients with chronic midportion Achilles tendinopathy be treated with a rehabilitation program that emphasizes resistance exercises using heavy loads, such as weighted heel raises (picture 8). Programs that emphasize the eccentric portion of exercise movements or that involve both the eccentric and concentric movements may be used. Tables describing a heavy slow resistance rehabilitation program (emphasizes both concentric and eccentric movement) (table 4) and an eccentric exercise rehabilitation program (table 5) are provided [3,35].

Patients may perform other regular exercise while participating in either type of rehabilitation program, provided that the activities do not exacerbate symptoms. Mild discomfort is permissible.

Concentric exercise involves a muscle shortening while working against a load; eccentric exercise involves a muscle lengthening while working against a load. As an example, when a person raises their body to the bar during a pull-up the biceps muscles are working concentrically, and when the person lowers their body to the ground the biceps muscles are working eccentrically.

Studies of rehabilitation programs for chronic midportion Achilles tendinopathy that emphasize the eccentric portions of resistance exercise using heavy loads have found this approach to be an effective nonsurgical treatment [36]. Other research suggests that programs using heavy resistance exercise emphasizing both the concentric and eccentric movements produce comparable outcomes [35,36]. Ultrasound and MRI studies performed during the long-term follow-up of patients who participated in rehabilitation programs involving heavy resistance training of either type (eccentric or combined concentric/eccentric loading) show normalization of tendon tissue appearance [37].

Eccentric exercise training — Small controlled trials and uncontrolled studies have found that eccentric exercise using heavy loads and involving the gastrocnemius and soleus muscles reduces pain at 12 weeks and long-term follow-up (two to five years) and shortens the time needed to return to sports [3,38-41]. A systematic review found there was higher-quality evidence supporting the use of eccentric exercise than alternative treatments for midportion (ie, not insertional) Achilles tendinopathy [34,42]. It is not known whether eccentric exercise prevents tendon injury or chronic tendinopathy in runners or other athletes. A table describing the most rigorously studied eccentric training rehabilitation protocol is provided (table 5) [3]. (See 'Prevention' below.)

Heavy slow resistance training — According to the results of a well-performed, single-blinded randomized trial involving 58 patients with chronic Achilles tendinopathy, heavy slow resistance training emphasizing both the concentric and eccentric portions of the selected exercises produced the same improvements in symptoms, function, and tissue appearance on ultrasound achieved by patients following a training program that emphasized only the eccentric portion of exercises [35]. The improvements were sustained at one-year follow-up. Of note, patient compliance was significantly better among patients performing the heavy slow resistance rehabilitation (92 versus 78 percent in the eccentric training group). This improved compliance may have been related to the time required, which was 107 minutes per week for the heavy slow resistance training and 308 minutes per week for the eccentric training. The training program used in the study is summarized in the attached table (table 4).

Shoe-based interventions — Various modifications and inserts for shoes have been prescribed for chronic Achilles pain. Some are suggested as adjuncts to eccentric exercise. Such interventions include the following:

●Heel lifts – Limited evidence suggests that heel lifts reduce pain associated with Achilles tendinopathy. We suggest to our patients that they use heel lifts, usually one to two centimeters, whenever they are weight-bearing for approximately 12 weeks. Shoes with a higher heel (many running shoes are constructed in this manner) may serve the same purpose.

Biomechanical studies suggest that the addition of an in-shoe heel lift to standard running shoes reduces loads on the Achilles tendon during activity [43,44]. These findings support the use of heel lifts in the rehabilitation of Achilles tendon disorders in which a goal of treatment is to lower tension within the tendon.

In a randomized trial of 100 patients with mid-portion Achilles tendinopathy confirmed by ultrasound, use of a heel lift led to statistically significant reductions in pain and improvements in function compared with eccentric exercises at 12 weeks [45]. However, the improvements reported did not meet the authors' predetermined thresholds for clinically significant difference. Observational evidence supports the effectiveness of heel lifts in reducing pain from Achilles tendinopathy [46].

●Shoe wear and inserts (eg, orthotics) – Arch supports, orthotics, and running shoes that are stable and prevent over-supination are commonly prescribed for Achilles tendinopathy and other causes of heel and foot pain, but studies supporting these interventions are limited and no clear benefit has been demonstrated in Achilles tendinopathy [47,48]. A softer heel counter may be more comfortable for patients with Achilles tendinopathy. Night splinting is not beneficial [49]. Running shoe selection is discussed in detail separately. (See "Running injuries of the lower extremities in adults: Risk factors and prevention", section on 'Running shoes'.)

●Heel brace – Two small, randomized trials, one sponsored by the manufacturer of the AirHeel brace, report improved symptoms and function in patients with chronic Achilles tendinopathy treated with a cushioned heel brace [50,51]. Further study is needed.

Adjunct interventions — Various treatments have been prescribed for chronic Achilles pain. According to two systematic reviews, high-quality evidence supporting these interventions is lacking [34,42]. Some are suggested as adjuncts to eccentric exercise. Such treatments include the following:

●Massage therapy – Soft tissue manipulation therapies, including pressure massage, may be useful adjunct treatments for Achilles tendinopathy. In one small randomized trial, patients treated exclusively with pressure massage had no difference in outcome compared with those treated with physical rehabilitation featuring eccentric exercise [52].

●Extracorporeal shockwave therapy – Extracorporeal shockwave therapy (ESWT) uses pressurized air or electromagnetic pulses to deliver shockwaves and is used to treat a variety of chronic, soft tissue disorders. Low-quality evidence suggests that ESWT may be an effective adjunct treatment for Achilles tendinopathy and it is considered a safe intervention [53]. We believe that ESWT is a reasonable therapy to use should Achilles tendinopathy fail to improve with two to three months of physical rehabilitation and associated conservative measures. The use of ESWT for chronic tendinopathy is discussed in greater detail separately. (See "Tendinopathy: Overview of management", section on 'Extracorporeal shock wave therapy'.)

●Topical nitroglycerin (glyceryl trinitrate) – Given its safety, low cost, and limited evidence of benefit in studies of tendinopathy, we believe topical nitroglycerin (NTG) is a reasonable adjunct treatment. However, studies of topical NTG for Achilles tendinopathy report inconsistent results [54-56].

The dose in most studies is either one-fourth or one-half of a 5 mg/24-hour or 10 mg/24-hour patch, used continuously and replaced daily for three to six months. The use of topical NTG for tendinopathy is discussed in greater detail separately. (See "Tendinopathy: Overview of management", section on 'Topical nitroglycerin (glyceryl trinitrate)'.)

●Glucocorticoid injection – We do not use glucocorticoid injection as a treatment for Achilles tendinopathy. However, such injection may provide short-term symptom relief in some patients, thereby enabling more active participation in exercise therapy. Evidence is mixed and there are case reports of Achilles tendon rupture after glucocorticoid injection [57]. Glucocorticoid therapy for tendinopathy and the risks associated with such treatment are discussed in greater detail separately. (See "Tendinopathy: Overview of management", section on 'Glucocorticoids' and 'Epidemiology and risk factors' above.)

In a well-blinded, randomized trial of 100 patients with Achilles tendinopathy causing symptoms for a minimum of three months, those treated with glucocorticoid injection in addition to exercise therapy experienced greater functional and symptomatic improvement at three and six months than patients given placebo injections in addition to exercise therapy [58]. However, no significant difference in functional outcomes or tendon thickness was noted at 12 or 24 months. No severe adverse events occurred in either group.

Unproven interventions — The effectiveness of the interventions described below for the treatment of Achilles tendinopathy is unproven, and we do not use them as part of standard therapy. (See "Tendinopathy: Overview of management", section on 'Investigational treatments'.)

●Percutaneous ultrasonic tenotomy (PUT) – PUT involves inserting a needle-like probe into a damaged tendon. The probe tip oscillates, producing ultrasonic energy that breaks down damaged tissue. The resulting debris is removed with an irrigation system that is part of the device. Although commonly performed to treat a range of chronic tendinopathies, PUT has not been studied in well-controlled, prospective clinical trials. In a retrospective chart review of 34 patients with insertional Achilles tendinopathy, the percentage of those with moderate to severe pain was reduced from 68 to 15 percent among those treated with PUT [59]. A systematic review of seven studies of PUT, including one of Achilles tendinopathy, reported improvements in pain and function in patients with elbow tendinopathy but only modest, short-term improvements in patients with Achilles tendinopathy [60].

●High-volume injection – This intervention (sometimes referred to as a Brisement procedure) involves injecting a high volume of fluid (typically isotonic saline, glucocorticoid, and local anesthetic) under ultrasound guidance into the para-tendon, with the intent of reducing pain by disrupting abnormal blood vessels and peripheral nerves. Preliminary studies suggest possible benefit in patients with Achilles tendinopathy, including earlier return to sport, but further study is needed [61-63].

●Platelet-rich plasma injection (PRP) – Although PRP is commonly administered for Achilles tendinopathy, there is no high-quality evidence supporting its effectiveness, and we do not support its use for this indication [64]. Multiple randomized trials comparing PRP injection with placebo injection and eccentric load exercise have found no statistically significant differences between groups in symptoms or functional outcomes [65-68]. The use of PRP and other biologic therapies in the treatment of tendinopathy is discussed in detail separately. (See "Biologic therapies for tendon and muscle injury".)

●Low-level laser therapy – According to a systematic review of four studies, there is no high-quality evidence supporting the use of low-level laser therapy as an adjunct treatment for Achilles tendinopathy [69].

Although used by some clinicians, the local injection treatments listed below lack high-quality evidence supporting their use for Achilles tendinopathy.

●Polidocanol injection – Polidocanol is a detergent used to treat telangiectasias and varicose veins. (See "Injection sclerotherapy techniques for the treatment of telangiectasias, reticular veins, and small varicose veins", section on 'Polidocanol'.)

●Aprotinin injection – Aprotinin is a protein that inhibits several proteases. (See "Thrombotic and hemorrhagic disorders due to abnormal fibrinolysis", section on 'Aprotinin'.)

●Fibroblast injection – This treatment involves injecting laboratory-expanded, skin-derived fibroblasts suspended in autologous plasma into the injured portion of a damaged tendon.

●Prolotherapy – Prolotherapy involves injecting a natural irritant into injured soft tissue. Limited evidence suggests that prolotherapy may be a useful adjunct to treatment with resistance exercise [70].

●Dry needling – Dry needling involves repeated puncture of the tendon at the site of pain using a small needle with the intent of stimulating an inflammatory response, formulation of granulation tissue, and promotion of tendon healing. A small randomized trial reported no additional benefit from dry needling among patients treated with heavy-load exercise rehabilitation [71]. (See "Tendinopathy: Overview of management", section on 'Dry needling'.)

FOLLOW-UP CARE — 

Although no studies demonstrate the benefit of eccentric exercise in the prevention of acute Achilles tendon injury, we suggest that patients continue to perform these exercises once rehabilitation has been completed and symptoms have resolved. We believe this may be of particular benefit to athletes embarking upon a more intense training regimen. (See 'Chronic tendinopathy' above.)

Some patients treated for chronic Achilles tendinopathy have persistent symptoms, but it is unclear whether this is true of patients who complete a properly designed rehabilitation program emphasizing heavy resistance exercise. Patients who do not fully recover may experience reinjury [72].

COMPLICATIONS — 

The most common complication of Achilles tendinopathy is chronic pain, which limits daily, recreational, and sports activities. Chronic tendinopathy increases the risk of tendon rupture, a painful, debilitating injury often requiring surgical repair.

PREVENTION

Ultrasound screening — The widespread use of musculoskeletal ultrasound in sports medicine has increased the feasibility of screening athletes for tendinopathy. However, while there is growing evidence that abnormal tendon appearance on ultrasound may be associated with the development of Achilles tendinopathy, controlled trials assessing patient-important outcomes are lacking [73]. Structural anomalies in tendons are commonly seen in asymptomatic tendons. Clinicians caring for athletes (particularly elite or professional athletes) participating in sports that place high stress on the Achilles tendon may choose to perform regular ultrasound examinations looking for signs of tendinopathy, but there is little evidence to support this approach.

General measures — Several interventions may reduce the risk of developing new or recurrent Achilles tendinopathy and other injuries of the lower extremity. Such interventions, particularly among runners, are discussed in detail separately. Interventions and studies of special relevance to preventing tendinopathy and tendon rupture of the Achilles are described below. (See "Running injuries of the lower extremities in adults: Risk factors and prevention", section on 'Training suggestions to reduce injury risk'.)

Before engaging in any vigorous exercise, it is important to perform an appropriate dynamic warm-up. Although few studies have assessed the Achilles tendon specifically in this regard, the findings of a prospective, observational study of infantry recruits suggest that performing such a warm-up and avoiding cold-weather training reduces the risk of Achilles tendinopathy [4]. Additional support, such as taping (picture 7) or a neoprene sleeve (picture 9) that extends over the course of the tendon, may be helpful for some patients as they resume activity.

Strengthening of the tendon and of the ankle and foot generally may reduce the risk for recurrence. This is discussed above. (See 'Follow-up care' above.)

Clinical studies evaluating the impact of stretching specifically upon Achilles tendinopathy are lacking. Nevertheless, many clinicians believe imbalances in muscle strength or flexibility predispose some athletes to injury. We believe it is reasonable to include stretching following exercise or a dynamic warm-up as part of an Achilles injury prevention regimen. Typical techniques include stretching the gastrocnemius and soleus muscles while bracing one's hands against a wall. Stretches are performed both with the knee bent and straight. The stretch can be performed by standing on the edge of a step and letting the heel descend gradually (picture 10), or by dorsiflexing the foot while seated using a towel or stretch band. It may be helpful for patients to undergo assessment by an athletic trainer, physical therapist, or sports medicine specialist to identify imbalances in flexibility or strength and to receive instruction in appropriate training techniques.

Although high body mass index (BMI) is associated with tendon problems, no studies clearly show that weight loss prevents such problems. Nevertheless, common sense suggests that patients with obesity should try to lose weight in order to reduce strain on the lower extremity, among many other health benefits. (See "Obesity in adults: Overview of management" and "Overweight and obesity in adults: Health consequences".)

Measures for patients on fluoroquinolones — The risk of fluoroquinolone-associated tendon problems is low overall but higher than that associated with other antibiotics. The incidence of Achilles tendinopathy is approximately 3 to 4 per 100,000 persons but increases with age. Details of the risks associated with fluoroquinolones, and tendon problems specifically, are discussed separately. (See "Fluoroquinolones", section on 'Tendinopathy'.)

In general, we prefer to avoid treatment with fluoroquinolone in a patient with known tendinopathy or tendon injury if an equally effective alternative treatment with a better safety profile is available. Inactive patients with Achilles tendinopathy who require treatment with a fluoroquinolone should be apprised of the risks for tendon injury associated with these antibiotics and advised to avoid new or intense sport activities until several weeks after they have stopped taking them.

For athletes or highly active patients who require treatment with a fluoroquinolone, it is reasonable to take precautions to reduce the risk of Achilles tendinopathy or tendon rupture. High-quality evidence to determine what measures are most effective is lacking, but the following steps are reasonable [74]:

●General measures – Beginning with the first fluoroquinolone dose, athletes should reduce their training volume and intensity and maintain these reductions throughout the course of antibiotics. No high-intensity training or ballistic activities (eg, sprinting, jumping, full-speed scrimmages or competition) should be performed until two to four weeks after the completion of fluoroquinolone therapy.

●Runners – Runners should decrease total mileage to 60 percent of normal training and avoid hill and speed interval training while taking the fluoroquinolone. Runners who remain free of symptoms two weeks after the completion of therapy may increase mileage by 10 percent per week but should not implement speed or hill training for two additional weeks. If they choose to race during this time, they should be informed that there may be a higher risk of Achilles tendon rupture.

●Field and court athletes – Athletes who participate in field sports (eg, soccer, football) or other multidirectional activities (eg, tennis) that increase the risk of Achilles injury may choose to resume normal activity and competition two to four weeks after the completion of fluoroquinolone therapy. Athletes who resume full activity sooner than four weeks should be informed that there may be a higher risk of Achilles tendon rupture.

●Return to full activity – Athletes who have no symptoms during therapy and complete the full course of the antibiotic can begin a graduated return to full activity as described above but should monitor themselves closely for any musculoskeletal symptoms at or around the Achilles tendon. They should cease all athletic activity should symptoms develop during this period and be assessed by a knowledgeable clinician. Assuming there is no injury, they may resume a graduated return to full activity once symptoms resolve.

●Athletes who develop symptoms of tendon injury – Athletes who develop symptoms or tenderness around the Achilles tendon while taking a fluoroquinolone antibiotic or in the first three to six months after beginning this treatment merit evaluation to assess for findings of tendinopathy or other injury. (See 'Diagnostic imaging' above.)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: General issues in muscle and tendon injury diagnosis and management" and "Society guideline links: Achilles tendon injury".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Achilles tendon injury (The Basics)" and "Patient education: How to use crutches (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Epidemiology and mechanism of injury – Acute Achilles tendon pain generally develops when athletes abruptly increase their training intensity. Chronic tendon pain (>3 months) may result from sustained stress, poor running mechanics, or improper footwear. Rupture occurs when a sudden shear stress is applied to an already weakened or degenerative tendon. (See 'Epidemiology and risk factors' above and 'Mechanism of injury and pathophysiology' above and "Achilles tendon rupture".)

●Clinical presentation – Patients with Achilles tendinopathy typically experience pain or stiffness 2 to 6 cm above the posterior calcaneus. They are likely to be casual or competitive athletes who have recently increased their training intensity. Pain increases with activity and diminishes with a period of rest. (See 'Clinical presentation' above.)

●Physical examination – Examination should include palpation of the tendon for tenderness, thickening, or a defect. Note that edema or a hematoma may mask a defect. Patients with tendinopathy typically have localized tenderness 2 to 6 cm above the tendon insertion. Pain at the insertion point suggests calcaneal bursitis or possibly enthesopathy. (See 'Physical examination' above.)

The calf squeeze (ie, Thompson compression) test provides an accurate means for detecting complete Achilles tendon rupture (picture 5).

●Diagnostic imaging – Achilles tendinopathy (without rupture) is a clinical diagnosis. Imaging is often unnecessary. Plain radiographs are generally unhelpful. Musculoskeletal ultrasound and MRI are accurate tests that can be used to aid in the diagnosis of Achilles tendon rupture, particularly if examination findings are unclear but clinical suspicion remains high. (See 'Diagnostic imaging' above.)

●Differential diagnosis – Pain arising from the region between the posterior calcaneus and the gastrocnemius-soleus muscle complex may be caused by a number of conditions (table 3). Conditions commonly confused with Achilles tendinopathy include retrocalcaneal and subcutaneous calcaneal bursitis, calcaneal apophysitis, and Achilles enthesopathy. (See 'Differential diagnosis' above.)

Ankle sprain is the most common misdiagnosis when tendon rupture is the actual cause of pain. Do not assume rupture is absent because the patient can plantarflex or walk (table 2). (See "Achilles tendon rupture".)

●Indications for referral – Chronic tendinopathy that fails to improve with three to six months of conservative treatment may benefit from consultation with a specialized runners' clinic, sports medicine specialist, physical therapist, or orthopedic surgeon. (See 'Indications for referral' above.)

●Management – Acute Achilles tendinopathy is treated in standard fashion with relative rest, ice, and tendon support (eg, heel lift).

For chronic midportion tendinopathy (>3 months symptoms), we recommend treatment with a rehabilitation program that emphasizes resistance exercise using heavy loads (table 5) rather than other interventions (Grade 1B). Rehabilitation protocols that emphasize concentric and eccentric movements or only eccentric movements are both reasonable approaches. Slight heel lifts or shoes with higher heels (eg, many types of running shoe) may improve symptoms. Exercise programs and other interventions for chronic Achilles tendinopathy are discussed in the text. (See 'Acute tendinopathy' above and 'Chronic tendinopathy' above.)

●Prevention – Several interventions may reduce the risk of developing lower extremity injuries, including Achilles tendinopathy. (See "Running injuries of the lower extremities in adults: Risk factors and prevention", section on 'Training suggestions to reduce injury risk' and 'Prevention' above.)

ACKNOWLEDGMENT — 

The editorial staff at UpToDate acknowledges Peter Ham, MD, who contributed to an earlier version of this topic review.