CAUSE AND DIAGNOSIS OF PFPS There are several clinical findings and tests for patellofemoral pain syndrome (PFPS) in the literature. Cook et al. (2010) evaluated clinical tests in a systematic review and found the following: - Cluster 1: 1) Retropatellar pain during muscle contraction of the quadriceps against resistance by the examiner 2) Pain reported by the patient during squatting --> 35% Sensitivity, 89% specificity, LR 3.3, LR- 0.73 for both positive tests Cluster 2: 1) Retropatellar pain