Differential Diagnosis for Distal Anterior Knee Pain

Primary Diagnostic Considerations

The American Academy of Family Physicians recommends that pain localizing to the inferior pole of the patella, exacerbated by activities involving repetitive loading of the patellar tendon, is indicative of patellar tendinopathy, particularly in athletes and nonathletes with repetitive loading 1
The American Academy of Family Physicians suggests that physical examination reveals tenderness at the inferior patellar pole with the leg fully extended during resisted leg extension, and a decline squat test reproduces pain by placing increased load on the patellar tendon 1
The American College of Radiology states that infrapatellar fat pad impingement (Hoffa's disease) causes anterior knee pain and can be diagnosed on MRI, particularly with contrast enhancement, with enhancing synovitis thicker than 2 mm in Hoffa's fat correlating with peripatellar pain 2

The Journal of the American Academy of Orthopaedic Surgeons reports that patients with osteochondritis dissecans present with knee pain and swelling, often accompanied by mechanical symptoms including locking, catching, popping, or giving way, and physical examination may reveal tenderness, effusion, loss of motion, or crepitus 3, 4
The American College of Radiology recommends that subchondral insufficiency fractures, which most commonly involve the medial femoral condyle in middle-aged to elderly females, can present with anterior knee pain, and MRI identifies these fractures earlier than radiographs 2
The American College of Radiology states that bone marrow lesions are associated with increased knee pain, especially in males or patients with a family history of osteoarthritis 2, 5

The American Academy of Family Physicians suggests that the initial evaluation should document focal tenderness location, presence of effusion, weight-bearing ability, gross deformity, palpable mass, and any mechanical symptoms, and perform specific provocative tests such as decline squat for patellar tendinopathy 1, 5
The Journal of the American Academy of Orthopaedic Surgeons and the American College of Radiology recommend that for chronic anterior knee pain, radiographs should include frontal projection, tangential patellar view, and lateral view, and MRI should be considered when initial radiographs are normal but pain persists 3, 4, 5
The American College of Radiology states that MRI with contrast is more accurate for diagnosing Hoffa's disease, deep infrapatellar bursitis, and adhesive capsulitis 2