| Condition | Historical features | Common symptoms | Key findings | Additional comments |
| Poorly localized pain |
| Patellofemoral pain syndrome | - History of overuse, often involves running with a change in training (eg, increased mileage or pace).
| - Diffuse anterior, peripatellar pain.
- Knee may "give way".
- Pain increases with squatting, running (especially downhill), ascending or descending stairs, or arising after prolonged sitting.
| - Tenderness under medial or lateral patella.
- Normal knee motion.
- Effusion rare.
- Positive special testing (eg, patellofemoral compression test).
- Vastus medialis obliquus atrophy and hamstring, iliopsoas, and gastrocnemius tightness common.
- Lower extremity malalignment often present, especially during a single leg squat.
| - Most common condition seen in adolescents referred to sports medicine specialists.
- Knee effusion, abnormal knee motion, or ligamentous laxity require assessment for intra-articular damage.
|
| Patellar subluxation | - History of patella dislocation or hypermobility syndrome.
| - Anterior or medial knee pain.
- Popping or clicking from superolateral portion of the patella with movement.
| - Tenderness of the underside of the patella (patellar facets) and medial tenderness at the adductor tubercle.
- High-riding patella.
- Abnormal patellar tracking.
- Positive patellar apprehension test.
| - Plain radiographs are indicated to assess for avulsion fractures.
|
| Osteochondritis dissecans | - History of acute injury or highly active patient with pain that worsens with exercise.
| - Poorly localized pain with activity that may progress to stiffness, swelling, and mechanical symptoms of locking or catching.
| - Tenderness over the medial femoral condyle in the flexed knee.
| - Plain radiographs, including tunnel views of the knee, show crescent shaped lucency on the medial femoral condyle.
|
| Chronic ACL injury | - History of prior ACL injury.
| - Anterior knee pain with swelling, shifting, and giving way.
| - Ligamentous laxity on testing with anterior drawer, Lachman, and/or pivot shift testing.
- Knee effusion.
| - Meniscal injury also present in as many as 90 percent of patients with chronic ACL injury.
|
| Referred hip pain | - History of vague pain that may include the thigh.
- Depending upon etiology, pain may be worse with activity.
| - Poorly localized knee pain.
| - Normal knee examination.
- Limited range of motion at the hip.
| - Plain radiographs of the hips, including a frog leg view should be obtained.
- Slipped capital femoral epiphysis requires emergent orthopedic consultation.
|
Referred back pain
(L2/L3/L4 radiculopathy) | - Anterior knee pain is associated with anterior thigh pain and back pain.
- Numbness, paresthesias, or other sensory changes may be reported.
- Incontinence suggests cauda equina syndrome.
| - Anterior and medial knee pain associated with back pain that radiates into the medial foot.
| - Normal knee examination.
- Weakness of hip flexion, knee extension, and hip adduction.
- Sensation may be reduced over the anterior thigh down to the medial aspect of the lower leg.
- A reduced knee reflex is common in the presence of moderate weakness.
| - Rare in children.
- Plain radiographs and MRI of lumbar spine are indicated as is consultation with a pediatric neurologist or neurosurgeon, depending upon the findings.
|
| Patellar stress fracture | - Insidious onset of knee pain in highly active patients.
| | - Tenderness over patella at the fracture site.
| - Plain radiograph may show normal bone for months.
- MRI best for establishing the diagnosis.
- High risk for nonunion.
|
Malignant tumors
(eg, osteosarcoma, Ewing sarcoma, and leukemia) | - Minor trauma may be incidental and lead to evaluation.
- Pain can begin as mild and worsen with time and with exercise. Pain may be intermittent, especially with Ewing sarcoma.
| - Pain may or may not be well localized and is often worse at night.
- Fever may be present in patients with leukemia or Ewing sarcoma.
| - Tender soft tissue mass on examination.
- Knee range of motion may be limited.
| - Plain radiographs and blood studies (CBC with differential, CRP, ESR, serum alkaline phosphatase and lactate dehydrogenase) are indicated.
- Further evaluation depends upon initial findings.
|
| Benign tumors | - May come to light during evaluation for trauma.
| - Usually asymptomatic, may cause vague pain.
| - Tenderness at site of tumor sometimes present.
| - Plain radiographs show benign tumors as an incidental finding.
|
| Localized pain |
Osgood-Schlatter disease
(tibial tuberosity apophyseal avulsion) | - History of overuse, often with sports that involve jumping or cutting.
- Common during growth spurt.
- Pain increases with activity or direct pressure on the tibial tubercle and decreases with rest.
| | - Tenderness at tibial tubercle.
- Focal swelling and warmth directly over the apophysis.
- No effusion or ligamentous laxity.
| - Imaging is not necessary unless the patient has atypical complaints (pain at night, pain that is unrelated to activity, acute onset of pain, associated systemic complaints) or pain that is not directly over the tibial tubercle.
|
Sinding-Larsen-Johansson disease
(patellar apophyseal avulsion) | - History of overuse, often with sports that involve jumping or cutting.
- Common during growth spurt.
- Pain increases with activity and decreases with rest.
| - Pain at inferior patellar pole.
| - Tenderness at inferior pole of patella.
- Focal swelling and warmth directly over the apophysis.
- No effusion or ligamentous laxity.
| - Imaging if atypical complaints (eg, pain at night, unrelated to activity, unable to bear weight or take 4 steps, morning stiffness with "gel phenomenon" or associated with systemic complaints).
- Plain radiographs show open apophysis, often with fragmentation (also seen in normal patients as well).
- US shows open apophysis (often with fragmentation), patellar tendon thickening, and infrapatellar bursitis.
|
| Patellar and quadriceps tendinitis | - History of overuse, especially activities involving running and jumping.
- Gradual onset of pain that steadily increases over time as activities continue.
- Worse in knee that is opposite of the dominant hand, especially for sports such as baseball, basketball, fencing, or tennis.
| - Pain with ballistic movements (eg, jumping, sprinting, cutting).
| - Patella: Tenderness along tendon, superior and inferior to patella.
- Tendon may feel thick compared to contralateral side.
- Quadriceps: Focal tenderness between superior patella border and body of the quadriceps muscle.
- Pain with resisted knee flexion.
- Both: Quadriceps and hip flexor tightness often present.
| - Patellar tendinitis more common than quadriceps tendinitis.
- Tendinitis is more common in children while a tendinopathy reflects a degenerative cascade that is more commonly seen in adults.
- Ultrasound can show characteristic tendon changes.
|
Fat pad impingement
(Hoffa disease) | - Pain worse with terminal extension, especially in dancers, gymnasts, jumping athletes (eg, basketball or volleyball), or swimmers.
| - Vague achy pain deep to the patellar tendon which can be abrupt and sharp at specific angles of flexion or extension.
| - Diffuse patellar and fat pad tenderness.
- Pain with knee extension against resistance.
- Pain at terminal extension of the bounce home test.
| - Fat pad impingement may complicate patellar tendinitis, patellar fractures, or surgery.
- Infiltration of the fat pad with local anesthetic relieves the pain and can help differentiate impingement from other causes.
|
| Bipartite and tripartite patella | - History of strenuous activity.
| - Lateral or superolateral patellar pain.
| - Tenderness at the superolateral patella.
- Bony prominence at site of tenderness.
| - Plain radiographs show anomaly.
|
| Prepatellar bursitis | - History of overuse, especially direct repetitive knee trauma (eg, wrestling) or single direct trauma to the anterior patella.
| - Pain and swelling just below the patella.
| - Swelling below distal patella tendon insertion and around tibial tubercle.
- Skin redness over the prepatellar bursa.
- Normal knee range of motion.
| - Examination is typically sufficient to make the diagnosis.
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