The current study is aimed at examining the validity of five clinical patellofemoral tests used in the diagnosis of patellofemoral pain syndrome (PFPS). Forty-five knee patients were divided into either the PFPS or the non-PFPS group, based on the fulfilment of the diagnostic criteria for PFPS. An investigator, blinded to the group assignment, performed the vastus medialis coordination test, patellar apprehension test, Waldron's test, Clarke's test, and the eccentric step test. The positive likelihood ratio was 2.26 for both the vastus medialis coordination test and the patellar apprehension test. For the eccentric step test, the positive likelihood ratio was 2.34. A positive outcome on either the vastus medialis coordination test, the patellar apprehension test, or the eccentric step test increases the probability of PFPS to a small, but sometimes important, degree. For the remaining tests, the positive likelihood ratios were below the threshold value of 2, indicating that given a positive test result, the probability that the patient has PFPS is altered to a small, and rarely important degree. The negative likelihood ratios for all tests exceeded the threshold value of 0.5, suggestive of clinically irrelevant information. These data question the validity of clinical tests for the diagnosis of PFPS.