Table 1.

Differential Diagnosis of Localized Anterior Knee Pain

ConditionTypical FindingsDiagnostic Testing
Bipartite or multipartite patellaUsually asymptomaticRadiographs, including contralateral for comparison
Infrapatellar fat pad syndrome (Hoffa syndrome)Tenderness below inferior patellar pole, worse with resisted knee extensionRarely indicated
Osgood-Schlatter diseaseLocalized tibial tubercle tenderness in an adolescent or young adultRadiographs, compare with contralateral knee
Patellar fractureLocalized patellar tenderness or swelling over the anterior kneeRadiographs, including contralateral to rule out multipartite patella
Patellar subluxation/dislocationApprehension with lateral patellar pressure, abnormal medial/lateral patellar glideRadiographs if conservative therapy fails or patella is nonreducible
Patellar tendonitis (jumper’s knee)Localized patellar tendon tenderness, worse with resisted knee extensionRarely, consider MRI for chronic symptoms
Patellofemoral pain syndrome (Anterior knee pain syndrome)Tenderness over patellar body or facets; abnormal patellar tracking, medial/lateral glide, or tilt; increased Q-angle*Radiographs uncommon; consider if conservative therapy fails
Prepatellar bursitis (housemaid’s knee)Tenderness, erythema, or superficial swelling over patellaRarely indicated
Sinding-Larsen-Johansson diseaseLocalized inferior patellar pole tenderness in an adolescent or young adultRadiographs, compare with contralateral knee
TumorInsidious pain, swelling, or mass over anterior knee; night pain or systemic symptomsRadiographs; consider MRI or bone scan if radiographs are negative and clinical suspicion is high
  • * Q-angle: An approximate measure of patellofemoral alignment. The angle is formed by the intersection of a line from the anterior superior iliac spine to the center of the patella and a line from the tibial tubercle to the center of the patella. A normal q-angle is less than 10° in men and 15° in women.