Overview of hemarthrosis

INTRODUCTION — Bleeding into a joint is referred to as hemarthrosis and is an important cause of monoarticular joint pain and swelling. Hemarthrosis may be suspected on the basis of a suggestive history, physical examination, or imaging studies, but definitive diagnosis usually requires joint aspiration. The management is determined in part by the cause.

An overview of the causes, clinical manifestations, diagnosis, and management of hemarthrosis is reviewed here. The differential diagnosis of monoarthritis, techniques of joint aspiration (arthrocentesis), the approach to adults with a bleeding diathesis, and the diagnosis and management of hemophilia are described in detail separately. (See "Monoarthritis in adults: Etiology and evaluation" and "Joint aspiration or injection in adults: Technique and indications" and "Joint aspiration or injection in children: Indications, technique, and complications" and "Approach to the adult with a suspected bleeding disorder" and "Approach to the child with bleeding symptoms" and "Clinical manifestations and diagnosis of hemophilia" and "Treatment of bleeding and perioperative management in hemophilia A and B".)

CAUSES OF HEMARTHROSIS — The range of disorders that may result in hemarthrosis can be broadly grouped into traumatic and nontraumatic causes; the latter include bleeding disorders, neurologic deficits, arthritis, neoplasms, vascular damage, and other miscellaneous causes (table 1). (See 'Traumatic' below and 'Nontraumatic' below.)

Traumatic — Injuries are among the most common causes of hemarthrosis. In patients with normal sensation and without a bleeding diathesis, joint trauma is generally remembered. The pain is often severe [1]. However, pain may be minimal or absent immediately following the event. Patients with impaired sensation from neuropathy or myelopathy may have little or no pain despite the presence of a fracture. (See 'Knee injury' below and 'Lipohemarthrosis' below and 'Minimal injuries' below and 'Postoperative' below.)

Following a major injury with intraarticular bleeding, synovial fluid rapidly accumulates within the joint. The accumulation of bloody fluid is due to soft tissue injury or to bone or osteochondral fracture. Serious ligamentous, osseous, or cartilage damage may be suspected when joint swelling occurs within 12 hours after trauma, although swelling is present much earlier, sometimes within two hours, in many patients [2].

Knee injury — The knee is a frequent site of injury, and the majority of cases of posttraumatic hemarthrosis of the knee are associated with serious articular injury, often ligamentous and meniscal damage (table 2). Thus, evaluation for internal derangement is an important part of the assessment (see "Approach to the adult with unspecified knee pain"). The most common mechanism of injury in patients with acute hemarthrosis of the knee is forced twisting of the loaded joint [2,3].

Anterior cruciate ligament (ACL) tears are the most common cause, occurring in approximately 70 percent of patients with posttraumatic hemarthrosis of the knee [2]. Meniscal tears occur in 10 percent of patients, one-half of whom also have an ACL tear [1]. Patellar subluxation or dislocation occurs in 10 to 15 percent of patients, and osteochondral fracture fragments are found in 2 to 5 percent. Patellar subluxation may be a more common mechanism of hemarthrosis in children, accounting for 48 of 117 cases (41 percent) in one series [4]. Other lesions, such as posterior cruciate ligament injuries and capsule tears, occur in approximately 5 percent of patients.

Tenderness to palpation of the medial or lateral joint lines or the patella can indicate the site of injury [1]. Clinical tests for stability are performed with varus (for the lateral collateral ligament), valgus (for the medial collateral ligament), anterior (drawer test, for the ACL), and posterior (posterior draw or sag test, for the posterior cruciate ligament) stress (picture 1A-B). (See "Physical examination of the knee" and "Approach to acute knee pain and injury in children and skeletally immature adolescents", section on 'Evaluation'.)

The initial imaging technique of choice is plain film radiography of the involved joint and adjacent bones. For the knee, we usually obtain anterior-posterior, lateral, patellar, and tunnel views [5]. When a fracture is strongly suspected but radiographs are negative, computed tomography (CT) may aid in diagnosis. Magnetic resonance imaging (MRI) provides helpful information about ligamentous and cartilaginous structures that are not typically visible with plain radiographs or CT.

Arthroscopic evaluation of the knee provides an alternative approach to assessing the severity of knee damage when injury is accompanied by hemarthrosis, but should generally be performed only if advanced imaging is not informative. In a prospective study, all injured knees that had a traumatic hemarthrosis with little or no instability on clinical examination underwent arthroscopy and examination under anesthesia [6]. One-third of the knees had slight or no pain at the time of the injury. Some degree of disruption of the ACL of the involved knee was found in 71 percent of the patients examined, while a torn meniscus was present in 47 percent. A meniscal tear was frequently associated with injuries of varying severity to other joint structures. Other damage found during arthroscopy and examination under anesthesia included minor ligament sprains without laxity, major associated ligament injury, and femoral cartilage fractures or surface defects [6]. When examined without anesthesia, some patients with documented ACL tears did not have a positive drawer sign.

Lipohemarthrosis — Lipohemarthrosis, which is the presence of fat and blood in a joint cavity, is usually caused by intracapsular fractures or extensive intraarticular soft tissue injury [2]. Lipohemarthrosis can be detected by arthrocentesis, by CT scan or MRI, and/or plain radiology (image 1) [2,7]. While a single fluid-fluid level on cross-table plain radiographs is suggestive of lipohemarthrosis, this finding may also occur due to separation of intraarticular cellular and fluid components following intraarticular bleeding without the presence of fat in joint fluid [8]. The finding of a double fluid-fluid level is more specific for lipohemarthrosis [7]. The diagnosis can be suggested also by ultrasonography [9].

Minimal injuries — In patients in whom hemarthrosis occurs after minimal trauma, coagulation disorders, such as hemophilia, an acquired inhibitor to factor VIII, or other disorder of blood clotting should be suspected [10] (see "Approach to the adult with a suspected bleeding disorder"). When hemarthrosis following minimal trauma is not due to a bleeding diathesis, the most commonly documented injuries are ACL and meniscal tears [8,11].

Postoperative — Recurrent postoperative hemarthrosis is an uncommon complication of total knee arthroplasty, seen in approximately 1 percent of such patients, and is most often due to impingement of hypertrophic synovium by the prosthesis [12]. It may present at any point within the first year after surgery, and can be addressed by operative excision of the affected tissue or by embolization of feeding vessels. Hemarthrosis is also a potential but unusual complication after performing lateral releases or after arthroscopy [13-16].

Nontraumatic — A variety of hereditary, acquired, and iatrogenic bleeding disorders can result in hemarthrosis. Other potential causes are neurologic, infectious, and vascular diseases, arthritis, particularly osteoarthritis with associated chondrocalcinosis, and neoplasms. (See 'Bleeding disorders' below and 'Osteoarthritis' below and 'Neurologic disorders' below and 'Septic arthritis' below and 'Vascular disorders' below and 'Tumors' below.)

Bleeding disorders — Bleeding disorders should be considered as the underlying cause when hemarthrosis occurs with minimal or no trauma. Questions about bleeding during or after surgical or dental procedures, use of anticoagulant medications [17,18], and rarely, thrombolysis [19,20] or extreme dietary restriction (vitamin C deficiency) may help uncover the presence of a bleeding diathesis or its cause.

Initial laboratory tests include a complete blood count, prothrombin time (PT), and activated partial thromboplastin time (aPTT) (table 3). A bleeding time may be helpful if the history or physical examination suggests a platelet disorder; however, joint bleeding is typically seen with deficiencies in coagulation factors, rather than platelet abnormality (table 4). Unexplained abnormalities of any of these tests require further investigation, which is described in detail separately. (See "Approach to the adult with a suspected bleeding disorder".)

Hemarthrosis is the most common musculoskeletal manifestation of hemophilia [21]. Severe hemophilia (defined as less than 1 percent of normal factor activity) causes hemarthrosis in 75 to 90 percent of patients. The first attack usually occurs between two or three years of age. The knee is the most common joint involved, followed by the elbow, ankle, hip, and shoulder. Bleeding commonly recurs in a subset of joints, referred to as "target joints," that are at highest risk for permanent injury. Bilateral involvement is not uncommon [21]. (See "Clinical manifestations and diagnosis of hemophilia", section on 'Hemophilic arthropathy'.)

Three forms of hemarthrosis are recognized in patients with hemophilia: acute, subacute, and chronic.

●In acute hemarthrosis, the affected joint is painful, swollen, and warm, and range of motion is reduced. The clinical manifestations vary by age. In infants, early signs of bleeding include irritability and decreased use of the affected limb. In older children and adults, hemarthrosis is manifested by prodromal stiffness and, in some patients, by a characteristic "aura" (often a sensation of tingling or warmth), which is followed by acute pain and swelling [22]. One joint is usually affected at a time, but multiple bleeding sites are not uncommon. Symptoms respond rapidly to plasma and factor replacement, and as the effusion is reabsorbed, mobility returns.

●Untreated hemorrhage can lead to intraarticular damage in the subacute stage. In this stage, the toxic effects of blood products lead to synovial hypertrophy, fibrosis, and impaired joint movement. Despite marked internal derangement, joint pain is not prominent at this time.

●Repeated attacks or persistent hemorrhage for more than six months can lead to chronic disabling arthropathy, with symptoms sometimes mimicking osteoarthritis. Chronic arthropathy can affect 20 percent or more of patients with hemophilia [23].

The histopathology of hemophilic arthropathy is complex [24,25]. In early disease, the histology reveals synovial hypertrophy and fibrosis, changes similar to rheumatoid arthritis. Late disease is characterized by disruption of cartilage and by subchondral bone cyst formation. Cyst formation appears to reflect the combined effects of degeneration and interosseous bleeding [26-28]. Cartilage and bone destruction in affected patients appears to be the result of direct toxic effects of blood products, mechanical effects, and cytokines [26]. Iron, in the form of ferric citrate, stimulates human synovial fibroblasts to proliferate in vitro [29]. In vitro data suggest that blood can be toxic to human cartilage after as little as two days, a conclusion supported by studies of induced hemarthrosis in hemophilic rats [30,31]. Interestingly, susceptibility to joint injury may reflect in part the impaired wound healing observed in hemophilia, since wild-type animals subjected to experimental hemarthrosis exhibited more rapid clearance of joint bleeding than mice with inherited coagulation defects and were correspondingly protected from associated structural injury [32]. Murine studies suggest that blood vessel hyperplasia occurs in reaction to hemarthrosis, potentially predisposing to recurrent bleeding in a subset of joints characteristic of each patient ("target joints," defined as joints affected by at least three bleeding episodes within six months) [22,33]. Growing cartilage is most susceptible to blood-induced damage [34]. Thus, children with hemarthrosis should be treated aggressively to minimize joint injury.

Radiologically, five stages of hemophilic arthropathy are recognized [21]:

●Stage 1: Soft tissue swelling – Swelling secondary to direct bleeding, both into the joint and into the adjacent tissues.

●Stage 2: Osteoporosis – Development of osteoporosis and/or epithelial overgrowth associated with inflammatory hyperemia, especially marked in the knee and elbow.

●Stage 3: Osseous lesions – Disorganization of the joint with overgrowth of the epiphysis, squaring of the patella, and widening of the articular notch of the knee and the trochlea of the ulna; the articular cartilage remains intact.

●Stage 4: Cartilage destruction – Cartilage injury and secondary joint space narrowing.

●Stage 5: Joint disorganization – Complete loss of cartilage spaces with associated bony erosion and irregularity.

Radiographic assessment of hemophilic arthropathy tends to underestimate the joint destruction. MRI and CT allow for early evaluation of joint damage, subchondral cysts, and cartilage or synovial lesions.

Treatment of hemarthrosis in the setting of hemophilia is discussed separately. (See "Treatment of bleeding and perioperative management in hemophilia A and B", section on 'Hemarthroses'.)

Osteoarthritis — Hemarthrosis of the knee can occur as a result of osteoarthritis; however, this is uncommon as osteoarthritis usually only causes a small amount of bleeding, and should be regarded as a diagnosis of exclusion. The origin of bleeding in several reported cases was presumed to be from the peripheral arteries of the posterior horn of the lateral meniscus, which were found to have degenerative tears [35].

Neurologic disorders — Recurrent episodes of hemarthrosis can occur in patients with neuropathic arthropathy (Charcot joints). Note that Charcot joints are often still somewhat painful. (See "Diabetic neuroarthropathy".)

Septic arthritis — Hemarthrosis may occur without associated trauma in patients with bacterial arthritis, though this is rare [36]. (See "Septic arthritis in adults".)

Vascular disorders — Vascular fragility due to vitamin C deficiency may lead to hemarthrosis and subperiosteal bleeding [37] (see "Overview of water-soluble vitamins", section on 'Vitamin C (ascorbic acid)'). Peripheral arterial aneurysms or, more commonly, procedure-related pseudoaneurysms may rupture, resulting in intraarticular hemorrhage [38].

Tumors — The neoplasms most often associated with hemarthrosis are generally benign. Two important types are synovial hemangiomas (see 'Synovial hemangioma' below) and tenosynovial giant cell tumor (TCGT), historically known as pigmented villonodular synovitis (PVNS) (see 'Tenosynovial giant cell tumor/pigmented villonodular synovitis' below). Malignant tumors, both metastatic and those arising de novo in or near a joint, can lead to bloody effusions.

Synovial hemangioma — A synovial hemangioma is a rare benign vascular tumor that can occur in a joint, usually the knee. Children are more likely to have intraarticular hemangiomas than adults. Affected patients present with a recurrent painful monoarticular hemarthrosis [39].

Plain film radiography is normal in half of the patients or shows joint effusion, soft tissue swelling, and/or erosions. The presence of phleboliths is suggestive of hemangioma, but MRI is the modality of choice for diagnosis [40,41].

Synovial hemangiomas may be congenital, appearing as solitary neoplasms that infiltrate local tissue and adjacent neurologic structures. The margins of the mass are typically composed of both large and small vessels. Hemangiomas do not metastasize or undergo malignant transformation. Pathologic examination of hemangiomas shows spaces of various sizes, ranging from capillaries to cavernous sinusoids, which are lined by endothelium.

Tenosynovial giant cell tumor/pigmented villonodular synovitis — Tenosynovial giant cell tumor (TGCT), historically known as pigmented villonodular synovitis (PVNS), is a slow-growing, benign, but locally invasive tumor of the synovium. It most commonly involves the knee, but can also occur in the hip, ankle, and elbow. Episodic acute attacks of pain and swelling are associated with spontaneous hemarthrosis, but hemarthrosis may also be identified unexpectedly upon joint aspiration performed as part of the evaluation of a chronically swollen joint.

Most patients with knee involvement have difficulty in ambulation, and may experience locking and catching of the joint. This tumor-like growth may be driven by overexpression of colony stimulating factor 1 (CSF1, also known as macrophage-CSF [M-CSF]) by a minority of cells, driving recruitment and expansion of CSF1-responsive neighboring cells [42]. (See "Treatment for tenosynovial giant cell tumor and other benign neoplasms affecting soft tissue and bone", section on 'Tenosynovial giant cell tumor'.)

The synovial fluid classically is dark brown or hemorrhagic. A synovial biopsy may be diagnostic. The histopathology of TGCT can mimic rheumatoid arthritis, but TGCT affects few joints and rarely in a symmetrical fashion. It usually presents as a monoarticular hemarthrosis and it may exist in a diffuse or nodular form [43].

The diffuse form is characterized by a history of swelling that is not preceded by trauma. On physical examination, the majority of patients have distension of the suprapatellar pouch and a large effusion. As many as 40 percent may have a palpable diffuse synovial mass. This can be accompanied by periarticular erosions on plain radiographs.

The nodular form is less common and does not show the same destructive changes as the diffuse form. It can cause recurrent hemarthrosis, but the aspirate may be of normal color and not show the classic changes or radiographic findings.

The most common feature of TGCT on MRI is the presence of intraarticular nodules or masses. MRI findings are very useful in the diagnosis of TGCT, because hemosiderin in the tissues renders TGCT "dark" on all MRI sequences due to a characteristic lack of signal on both T1 and T2 images.

The treatment of TGCT is described in detail separately. (See "Treatment for tenosynovial giant cell tumor and other benign neoplasms affecting soft tissue and bone", section on 'Tenosynovial giant cell tumor'.)

CLINICAL MANIFESTATIONS

Symptoms and physical findings — The presentation of hemarthrosis varies with the etiology and is particularly influenced by the acuity or chronicity of bleeding (see 'Causes of hemarthrosis' above). Pain, stiffness, reduced range of motion, swelling, and warmth are typically present but can range from very mild to severe.

As an example, acute intraarticular bleeding, as occurs with trauma or from an acute hemophilic bleed, typically occurs immediately and is often intensely painful. However, subacute bleeding that occurs with articular tumors such as tenosynovial giant cell tumor (TGCT) may be identified as an unexpected finding upon joint aspiration performed as part of the diagnostic evaluation of a swollen joint. In such cases, joint swelling, stiffness, and mild to moderate discomfort may be the only presenting symptoms. (See 'Traumatic' above and 'Bleeding disorders' above and 'Tenosynovial giant cell tumor/pigmented villonodular synovitis' above.)

Patients with hemophilia may report a vague sensation of tingling or warmth at the onset of acute bleeding, termed an aura, followed by tightness and reduced motion, which is typically accompanied by increasing pain, warmth, and acute swelling. Knees are most commonly affected in this group, but elbows and ankles are commonly affected as well. (See 'Bleeding disorders' above.)

Synovial fluid analysis and other laboratory findings — Synovial fluid obtained from a patient with hemarthrosis may appear red, pink, or brown. Other abnormalities of the fluid may be noted that depend upon the cause of bleeding. As an example, the presence of lipid globules strongly suggests an intraarticular fracture, resulting in leakage of marrow fat into the synovial fluid (see 'Lipohemarthrosis' above). A true bloody effusion usually fails to clot due to chronic fibrinolysis, while blood from a traumatic aspiration generally does coagulate [36].

Following centrifugation of joint fluid, the aspirate from a patient with hemarthrosis will generally exhibit xanthochromia from lysis of the resident erythrocytes. This characteristic can help to distinguish a bloody or blood-tinged fluid due to a traumatic arthrocentesis from true hemarthrosis. (See 'Differential diagnosis' below and "Synovial fluid analysis".)

Laboratory findings on testing of peripheral blood depend upon the presence of comorbid conditions, but otherwise hemarthrosis alone does not cause changes in general laboratory testing.

Imaging — Standard plain radiography often suggests soft tissue swelling and joint effusion; in patients with chronic, recurrent hemarthrosis (eg, in hemophilia) additional changes may occur over time, including in cartilage and bone (see 'Bleeding disorders' above and "Clinical manifestations and diagnosis of hemophilia", section on 'Hemophilic arthropathy'). Rarely, patients with large effusions may exhibit a blood-fluid level that is evident on radiography.

Computed tomography (CT) is most sensitive to the detection of acute blood but does not provide soft tissue or cartilage information. Hemosiderin is easily identified as low signal intensity on joint magnetic resonance imaging (MRI). Echogenic intraarticular fluid seen on ultrasound also indicates articular hemorrhage.

Imaging, especially MRI, may provide clues to other etiologies for hemarthrosis including fracture, intraarticular vascular malformation, and tenosynovial giant cell tumor (pigmented villonodular synovitis).

DIAGNOSIS — The diagnosis of hemarthrosis is usually made by joint aspiration, which typically reveals joint fluid that is overtly and uniformly sanguineous, although with chronicity, the fluid can become rusty or brown in color. Centrifugation discloses xanthochromia (yellow-tinged discoloration) of the supernatant, from ruptured red blood cells, distinguishing hemarthrosis from bleeding due to trauma incurred during the procedure itself. By contrast, in a traumatic tap, the fluid will typically change color from less to more sanguineous over the course of the procedure, while the supernatant of a centrifuged sample will disclose typical straw-colored fluid.

Arthrocentesis is generally not required for diagnosis when the underlying cause is already known with confidence (eg, patients with hemophilia and a history of hemarthrosis, or patients with acute trauma and known intraarticular injury), and when important alternate diagnoses such as septic arthritis can be excluded clinically.

Aspiration of larger effusions should be performed using a needle of sufficient gauge (eg, 18-gauge) to permit evacuation to relieve capsular distension and pain. If there is diagnostic uncertainty, fluid should be sent for cytology to evaluate potential malignancy in addition to routine synovial fluid studies (cell count, differential, Gram stain, culture, and, if indicated, crystal analysis).

In patients with plain radiographic evidence of trauma, the diagnosis of hemarthrosis is further supported by the appearance of a blood-fluid level in larger effusions, which is occasionally present.

DIFFERENTIAL DIAGNOSIS — A wide variety of infectious and inflammatory conditions may cause an acute monoarthritis and could clinically mimic hemarthrosis. The history and physical examination frequently help to suggest the presence of a cause of likely hemarthrosis, such as trauma or hemophilia, or another articular disorder. The finding of hemorrhagic joint fluid on synovial fluid analysis is the key finding that distinguishes hemarthrosis from other disorders causing similar symptoms and physical findings. The differential diagnosis of acute monoarticular joint pain and swelling is reviewed in detail separately. (See "Monoarthritis in adults: Etiology and evaluation".)

The principal mimickers of hemarthrosis include traumatic arthrocentesis, resulting in bloody "contamination" of synovial fluid; many conditions that may cause arthritis that can present with acute joint pain and swelling; and chronic hemophilic arthritis, which can present in a clinical setting typically associated with acute hemarthrosis. The major conditions of importance in the differential diagnosis include:

●Traumatic arthrocentesis – A traumatic arthrocentesis is the most likely cause of a bloody synovial fluid sample when the aspiration is not initially bloody, but fresh blood appears after some synovial fluid has been withdrawn. In this case, centrifugation of the specimen to examine the appearance of the resultant supernatant is useful. A serous appearance of the synovial fluid supernatant suggests that fresh blood has been mixed with previously nonbloody fluid. A true bloody effusion usually fails to clot due to chronic fibrinolysis, while blood from a traumatic aspiration generally does coagulate. The aspirate from a patient with hemarthrosis will generally exhibit xanthochromia from lysis of the resident erythrocytes. (See 'Synovial fluid analysis and other laboratory findings' above and "Synovial fluid analysis", section on 'Categories of joint effusions'.)

●Acute monoarthritis – A number of medical conditions may present with similar clinical symptoms to hemarthrosis, but the major differentiating factor is nonhemorrhagic joint effusions, in addition to the history and physical examination findings that typify other disorders. Major conditions that may also cause acute pain and joint swelling, similar to hemarthrosis, can be excluded by history and synovial fluid analysis. These conditions include:

•Bacterial septic arthritis – Bacterial septic arthritis typically presents with concomitant fever, and the diagnosis of septic arthritis can be confirmed with synovial fluid analysis and culture (see 'Septic arthritis' above and "Septic arthritis in adults"). In hemarthrosis, body temperature is often not elevated, there are minimal white blood cells in the synovial fluid, and the culture should be negative.

•Crystal arthropathy – The diagnosis of a crystal arthropathy (gout or calcium pyrophosphate deposition disease) is often suggested by the medical history and made by the identification of crystals on synovial fluid analysis. Occasionally, calcium pyrophosphate crystal deposition (CPPD) disease can present as "pseudo-hemarthrosis," with recurrent bleeding particularly affecting the shoulder, especially in the context of concomitant osteoarthritis [44]. (See "Clinical manifestations and diagnosis of gout" and "Clinical manifestations and diagnosis of calcium pyrophosphate crystal deposition (CPPD) disease".)

•Reactive arthritis – Reactive arthritis can generally be distinguished by the characteristic history of antecedent infection and differentiated from hemarthrosis by synovial fluid analysis. (See "Reactive arthritis".)

•Lyme arthritis – Lyme arthritis may be characterized, like hemarthrosis, by large joint mono- or oligoarthritis, especially of the knee, but occurs in an endemic region and may have other typical historical and physical features such as a prior tick bite and typical rash; the diagnosis of Lyme disease can generally be confirmed (or excluded) by serologic testing. (See "Musculoskeletal manifestations of Lyme disease" and "Diagnosis of Lyme disease".)

•Primary inflammatory arthropathies – Primary inflammatory arthropathies (which may also present with a mono- or oligoarthritis), such as rheumatoid arthritis, juvenile idiopathic arthritis, and spondyloarthritis, can mimic hemarthrosis when only one or a few joints are involved, but can be distinguished by medical history, examination, and synovial fluid analysis. (See "Diagnosis and differential diagnosis of rheumatoid arthritis" and "Oligoarticular juvenile idiopathic arthritis" and "Polyarticular juvenile idiopathic arthritis: Clinical manifestations, diagnosis, and complications" and "Systemic juvenile idiopathic arthritis: Clinical manifestations and diagnosis" and "Diagnosis and differential diagnosis of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults" and "Clinical manifestations and diagnosis of peripheral spondyloarthritis in adults".)

●Chronic hemophilic arthropathy – In patients with hemophilia and recurrent intraarticular bleeding, it may be difficult to distinguish new hemarthrosis from exacerbations of pain from underlying chronic joint injury. In both cases, patients present with pain, limited motion, swelling, stiffness, and joint warmth, although an acute painful episode combined with overt joint fullness (ie, substantial effusion) and a patient report of new tenseness in the joint should suggest hemarthrosis [45]. In some cases, patients with hemarthrosis report an aura (tingling or warmth) in the joint prior to new swelling and pain, providing another potentially helpful clue [45]. (See "Clinical manifestations and diagnosis of hemophilia", section on 'Hemophilic arthropathy'.)

POSTDIAGNOSTIC EVALUATION — Once the diagnosis of hemarthrosis has been established, the further management depends in part upon the cause; for example, orthopedic management should be undertaken for acute injuries or factor replacement should be administered in hemophiliacs. Thus, in patients in whom no cause is immediately evident on history, examination, and synovial fluid analysis, additional studies, such as further history, laboratory testing, imaging, and/or cytology, may be required to evaluate the possibility of a more subtle intraarticular lesion, intraarticular neoplasm, or other disorder.

In patients with bleeding that occurs with minor or no trauma, evaluation for coagulopathy should be undertaken if that diagnosis has not been previously established. Patients suspected of a coagulopathy should be referred to a hematologist with expertise in coagulation disorders.

TREATMENT — Treatment of hemarthrosis can be divided into interventions that are generally useful for any patient with acute hemarthrosis, and more specific treatments directed toward the underlying disorder. (See 'General approach' below and 'Cause-specific interventions' below.)

General approach — The goals of initial treatment are to limit further joint injury and optimize patient comfort. We advise the following approach, based upon case series and expert opinion [46-48]:

●Initial/acute therapy

•Patients with acute posttraumatic hemarthrosis should be treated initially by immobilization of the affected joint, application of ice, and compression.

•In patients with a tense effusion and those in whom the diagnosis is uncertain, aspiration of the joint may help provide pain relief.

•Potent analgesics may be required while the diagnostic evaluation proceeds, but most nonselective nonsteroidal antiinflammatory drugs, other than cyclooxygenase (COX) 2 selective agents that don't affect platelet function, should be avoided in the first 48 to 72 hours because of the increased risk of bleeding associated with their use. The decision regarding whether to use opioid analgesics in patients unresponsive to nonopioid agents, and the type of agent in patients receiving such therapy, should be made on an individualized basis taking the patient's history of analgesic use into account.

●Postacute phase interventions

•Nonsteroidal antiinflammatory drugs (NSAIDs) may be employed when the acute hemorrhage risk has receded, 48 to 72 hours after the injury, unless coagulopathy evaluation or immediate surgical intervention is planned. The presence of a coagulopathy influences drug choices. (See 'Coagulation disorders/hemophilia' below.)

•Depending upon the rate and extent of the clinical response to initial measures, some patients may require immobilization, the application of ice, and compression for up to a week.

•Joint lavage is generally not indicated, other than potentially in patients with hemophilia with recurrent hemarthrosis (see 'Coagulation disorders/hemophilia' below), because an isolated episode of bleeding into the joint is unlikely to cause lasting injury.

Cause-specific interventions — In patients in whom a definite cause for the hemarthrosis can be identified, interventions specific to the particular etiology can be employed. (See 'After major trauma' below and 'Coagulation disorders/hemophilia' below and 'Patients receiving anticoagulation' below and 'Postoperative' below and 'Vascular causes' below and 'Benign tumors' below.)

After major trauma — Patients with major trauma and hemarthrosis should be evaluated and managed in collaboration with an orthopedic surgeon; such patients are at risk for significant bone and soft tissue injuries. (See 'Traumatic' above and 'Knee injury' above.)

The involved joint should be completely immobilized until radiographs have been obtained; in patients with evidence of a fracture or suspicion of an internal derangement, orthopedic consultation should be obtained. Although not all intraarticular fractures require operative intervention, the patient and radiographic findings should be reviewed with a clinician experienced in fracture care. Ligamentous and meniscal injuries generally do not require immediate operative intervention.

Coagulation disorders/hemophilia — The prevention and treatment of acute and chronic hemarthrosis in patients with known clotting factor deficiency is described in detail separately. (See 'Bleeding disorders' above and "Synovectomy for inflammatory arthritis of the knee" and "Treatment of bleeding and perioperative management in hemophilia A and B", section on 'Hemarthroses' and "Chronic complications and age-related comorbidities in people with hemophilia", section on 'Arthropathy' and "Hemophilia A and B: Routine management including prophylaxis", section on 'Prophylaxis versus on-demand therapy'.)

In hemophilic patients with recurrent hemarthrosis, the role of lavage to avoid the long-term consequences of recurrent hemarthrosis is uncertain, although observational but uncontrolled data suggest good outcomes with prompt arthrocentesis, saline lavage, and glucocorticoid instillation [49].

Use of the selective cyclooxygenase (COX) 2 inhibitors celecoxib and etoricoxib is safe and effective in patients with hemophilic arthropathy [50,51]. Since the selective COX-2 inhibitors do not interfere with platelet function and may be less likely to cause gastroduodenal damage than nonselective NSAIDs, this approach may be useful for treating chronic joint pain in those with clotting factor deficiencies who require an NSAID [48,52]. The use and safety of celecoxib are described separately. (See "Overview of COX-2 selective NSAIDs" and "NSAIDs: Adverse cardiovascular effects", section on 'Aspirin and other antithrombotic agents'.)

One small series reported reduction of both recurrent hemarthrosis and synovitis in three hemophilia patients treated with tumor necrosis factor (TNF) inhibitors for concurrent inflammatory arthritis, providing anecdotal support for this approach [53]. Further support comes from murine studies that have implicated TNF as a mediator of hemophilia-associated joint inflammation and injury [54,55].

Patients receiving anticoagulation — Clinically important hemarthrosis in patients receiving therapeutic anticoagulation is rare. Diagnostic or therapeutic arthrocentesis is usually well tolerated in these patients despite the use of such therapies [56]. In most patients, temporary immobilization and analgesics will be the only treatment necessary after correction, if needed, of excessive anticoagulation. In the unusual event of persistent or recurrent hemarthrosis, an anatomic cause should be sought [57]. If the patient is not at immediate risk of thromboembolism, reversal of anticoagulation may be appropriate, provided that the benefits outweigh the risks of thromboembolism. (See "Management of warfarin-associated bleeding or supratherapeutic INR" and "Joint aspiration or injection in adults: Technique and indications", section on 'Approach to the patient on anticoagulants' and "Management of bleeding in patients receiving direct oral anticoagulants".)

Postoperative — Patients with recurrent postoperative hemarthrosis may require revision surgery and should be referred to their orthopedic surgeon for further evaluation and management (see 'Postoperative' above). In one reported case, angiographically guided embolization controlled recurrent bleeding into the knee in a patient who required chronic anticoagulation [58].

Vascular causes — In patients with an aneurysm or pseudoaneurysm as the cause of intraarticular bleeding, surgical intervention is often required. In patients in whom surgical treatment is not feasible, endovascular treatment with arterial embolization may be an option [38,59]. (See 'Vascular disorders' above.)

Benign tumors — In patients with benign tumors that lead to hemarthrosis, arthroscopic or surgical synovectomy is usually the treatment of choice to prevent recurrent episodes of hemarthrosis. (See 'Tumors' above and "Synovectomy for inflammatory arthritis of the knee".)

PROGNOSIS — The prognosis of hemarthrosis varies with the specific cause. For trauma and tumors, the prognosis is typically that of the inciting process. Repeated intraarticular hemorrhage in hemophilia carries a high risk of chronic hemophilic arthropathy, experienced by 20 percent or more of patients even in the era of factor replacement [60-62]. (See "Clinical manifestations and diagnosis of hemophilia", section on 'Hemophilic arthropathy'.)

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: Hemophilia A and B".)

SUMMARY AND RECOMMENDATIONS

●Hemarthrosis, or bleeding into a joint, can occur from a variety of causes (table 1) and results in monoarticular pain and swelling. Diagnosis usually requires joint aspiration, which reveals red, pink, or brown synovial fluid; arthrocentesis is needed whenever septic arthritis is suspected. Arthrocentesis is generally not required for diagnosis when the underlying cause is known with confidence (eg, patients with hemophilia and a history of hemarthrosis, acute trauma), and when important alternate diagnoses such as septic arthritis can be excluded clinically. Other abnormalities of the fluid depend upon the cause of the bleeding. (See 'Causes of hemarthrosis' above and 'Diagnosis' above.)

●A true bloody effusion usually fails to clot due to chronic fibrinolysis, while blood from a traumatic aspiration generally does coagulate. Traumatic arthrocentesis is most likely if the aspiration is not bloody initially, but fresh blood appears after some synovial fluid has been withdrawn. (See 'Causes of hemarthrosis' above and 'Diagnosis' above.)

●Injuries are among the most common causes of hemarthrosis. The pain is often severe but may be minimal or absent immediately following the event. Patients with impaired sensation from neuropathy or myelopathy may have little or no pain despite the presence of a fracture. The rapid accumulation of bloody fluid that follows a major injury with intraarticular bleeding is due to soft tissue injury or bone/osteochondral fracture. (See 'Traumatic' above.)

●The knee is a frequent site of injury, and evaluation for internal derangement is an important part of the evaluation. The most common mechanism of injury in patients with acute hemarthrosis of the knee is forced twisting of the loaded joint. The initial imaging technique of choice is plain film radiography. If a fracture is strongly suspected but radiographs are negative, computed tomography (CT) may aid in diagnosis; however, magnetic resonance imaging (MRI) also provides helpful information about ligamentous and cartilaginous structures. Arthroscopic evaluation of the knee may be helpful in some patients. (See 'Knee injury' above.)

●Additional concerns in patients with traumatic hemarthrosis include lipohemarthrosis, recurrent postoperative hemarthrosis following total knee arthroplasty, and coagulation disorders, which should be suspected in patients in whom hemarthrosis occurs after minimal trauma. When hemarthrosis following minimal trauma is not due to a bleeding diathesis, the most commonly documented injuries are anterior cruciate ligament (ACL), meniscal tears, and patellar subluxations. (See 'Lipohemarthrosis' above and 'Minimal injuries' above and 'Postoperative' above.)

●A variety of hereditary, acquired, and iatrogenic bleeding disorders can result in hemarthrosis. Bleeding disorders should be considered when hemarthrosis occurs with minimal or no recollected trauma. Hemarthrosis is typically seen with deficiencies in coagulation factors, rather than platelets (table 4). Three forms of hemarthrosis due to hemophilia and other coagulopathies are recognized: acute, subacute, and chronic; and five stages of hemophilic arthropathy have been identified. (See 'Bleeding disorders' above.)

●Potential causes of hemarthrosis other than bleeding disorders and trauma include neurologic, infectious, and vascular disorders; inflammatory, degenerative, and crystalline arthritis; and neoplasms, including tenosynovial giant cell tumor (formerly termed pigmented villonodular synovitis). (See 'Nontraumatic' above and 'Osteoarthritis' above and 'Neurologic disorders' above and 'Septic arthritis' above and 'Vascular disorders' above and 'Tumors' above.)

●The treatment of hemarthrosis includes interventions that are generally useful for any patient with an acute hemarthrosis and more specific treatments directed toward the underlying disorder. Treatments of general benefit include immobilization, ice, and compression initially; analgesia; and arthrocentesis. Lavage is generally not required but can be considered (together with glucocorticoid instillation) for recurrent hemarthrosis associated with hemophilia. Nonsteroidal antiinflammatory drugs (NSAIDs) that interfere with platelet function should be avoided, and thus the use of cyclooxygenase (COX) 2 inhibitors is encouraged. Specific treatment can be employed when a definite cause for the hemarthrosis can be identified. (See 'General approach' above and 'Cause-specific interventions' above and 'After major trauma' above and 'Postoperative' above and 'Vascular causes' above and 'Benign tumors' above.)

●The approach to patients treated with anticoagulation is variable, depending upon the risk of reduced anticoagulation therapy. The treatment of patients with known clotting factor deficiency is described in detail separately. (See 'Coagulation disorders/hemophilia' above and "Treatment of bleeding and perioperative management in hemophilia A and B".)