Proprioception in Subjects with Patellofemoral Pain Syndrome: Using the Sense of Force Accuracy

Abstract Objective: Comparison of the ability of reproducing isometric quadriceps force in patients with patellofemoral pain syndrome [PFPS] and healthy normal control subjects. Methods: The Ipsilateral Limb Matching method was utilized to assess the acuity of the sense of isometric force in the quadriceps muscle. At first, participants produced 20 and 60% of quadriceps maximal voluntary isometric contraction using an isokinetic dynamometer and visual feedback, and then they attempted to reproduce the target forces without visual feedback. They were asked to estimate and reproduce the target forces based on their own perception of the quadriceps force used earlier during the isometric contraction with feedback. This test was performed in 20° and 60° of knee flexion. The absolute error, constant error and variable error were used to measure the subjects' errors in their perception of sense of force. Results: Seventeen patients with PFPS [19 to 39 years old] and 17 matched healthy controls participated. The results of the three-way analysis of variance disclosed a significant difference in absolute error [p = 0.05, F value = 8.29] and variable error [p = 0.00, F value = 55.50] between the two comparison groups. An interaction effect of knee position by group in the three-way analysis of variance showed that the patients with PFPS had more absolute error, constant error and variable error particularly with 60° of knee flexion. Conclusion: The sense of force may be impaired in patients with PFPS. This syndrome may cause changes in the afferent signals from the muscle receptors and subsequently lead to mismatching between central and peripheral mechanisms of the sense of force.