Acute patellofemoral pain: aggravating activities, clinical examination, MRI and ultrasound findings

Objective: To investigate acute anterior knee pain caused by overuse in terms of pain location, aggravating activities, findings on clinical examination and ultrasound/MRI examination. To determine if acute anterior knee pain caused by overuse should be classified as a subgroup of patellofemoral pain syndrome (PFPS). Methods: In a observational study design 30 army recruits with anterior knee pain (mean duration of pain 4 weeks) were examined using the PFPS pain severity scale (PSS), knee pain diagrams, standardised clinical examination, ultrasound and MRI examinations. Results: On PSS typical knee loading activities were the most painful, while sitting with knee bend for prolonged time caused surprisingly little pain. Pain was most commonly perceived in the peripatellar area (25 patients (83%)). The most common site of pain on clinical examination was the peripatellar area (25 patients (83%)), but other synovial covered structures including the fat pad of Hoffa (12 patients (40%)), the medial plica and the joint line (12 patients (40%)) were also involved. Only eight patients (27%) experienced pain on the patellofemoral compression test. Only discrete changes was detected on MRI/ultrasound. Conclusions: Acute anterior knee pain should be regarded as a subgroup of PFPS as both symptoms and clinical examination suggests this. The clinical examination with disseminated pain in all synovial covered structures is consistent with ideas of the importance of synovium in the genesis of pain.