The validity of the motion palpation test for determining patellofemoral joint articular cartilage damage

ObjectivesThis study investigated the validity of the motion palpation test (MPT) for pre-operatively grading patellofemoral joint articular cartilage damage.DesignRetrospective review of cases.ParticipantsConsecutive patients (N=188) with suspected patellofemoral joint articular cartilage damage.ProcedureThe medical records of patients who underwent clinical examination using the MPT and proceeded to undergo knee arthroscopy were reviewed.ResultsBased on arthroscopic findings the MPT revealed excellent overall sensitivity (87%), positive test predictive value (97%), and accuracy (85%), but specificity (33%) and negative test predictive values (10%) were poor. However, overall likelihood ratios for a positive (1.3) or negative (0.39) test indicated only a minimal increase in the likelihood of having articular cartilage damage with a positive test, and only a small decrease in ruling-out the condition with a negative test. With a severe MPT crepitation grade subclassification, sensitivity was 65%, specificity was 96%, positive test predictive value was 99%, negative test predictive value was 38%, and accuracy was 99%. For a moderate MPT crepitation grade sensitivity was 77%, specificity was 44%, positive predictive value was 81%, negative predictive value was 38%, and accuracy was 81%. For a mild MPT crepitation grade sensitivity was 66%, specificity was 51%, positive test predictive value was 77%, negative test predictive value was 38%, and accuracy was 62%. Positive likelihood ratios for MPT crepitation grade subclassifications revealed a large and likely conclusive increase in the likelihood of having articular cartilage damage for the severe condition (16.25, 95% CI 9.9, 22.6), but only a minimal likelihood for ruling-in the disease for mild (1.35, 95% CI −5, 7.7) or moderate (1.38, 95% CI −5, 7.7) conditions. Having a negative test was suggestive of only a small or minimal decrease in ruling-out the disease for all conditions (0.67–0.36).ConclusionsMPT is only useful as a physical examination tool for identifying patellofemoral joint articular cartilage damage when the crepitation grade subclassification is severe.