An evaluation of lower limb mechanical characteristics in people with patellofemoral pain syndrome during repeated loading

Abstract

Introduction: Patellofemoral Pain Syndrome (PFPS) is characterised by pain in the region of the patellofemoral joint during functional tasks, sporting activities or following prolonged sitting. Strength deficits are commonly reported, however, there is no empirical evidence to support alterations in lower limb control. The knee and ankle joints of the lower limb interact to allow force absorption during loading activities. It is plausible that this interaction is altered in people with PFPS. Aim: The purpose of this study was to evaluate the knee and ankle joint interaction in people with PFPS compared to healthy counterparts, during on-the-spot, repetitive, single-leg, hopping tasks. Participants: Ten participants with PFPS (symptom duration of 30.44 (28.56) months and VAS pain score of 2.6 (1.5) prior to testing) and ten healthy participants volunteered for the study. Participants were aged between 18 and 40 years and were matched for sex, age, height, body mass and limb dominance. Procedures: Each participant performed four trials of single-leg, on-the-spot hopping. These four trials were performed in a random order and at different cadences (132, 120, 108, 96 hops.min-1). A fifth trial was performed at the participant's maximal height of hopping. Spatiotemporal characteristics, joint kinematics and kinetics were recorded using synchronous collection of force plate (AMTI, Multicomponent force plate, Gen 5 BP400600-1000, Watertown, MA) and motion data (Optotrak Certus System, NDI, Waterloo, Canada). Variability was calculated as the coefficient of variation (CV). Repeated measures analysis of variation (ANOVA) were performed, followed by post hoc tests to determine differences between groups during the different efforts of hopping. Results: There were no statistically significant differences between groups for all spatiotemporal, kinematic, kinetic and CV scores for all dependant variables at the knee and ankle joints (p > 0.05). There was statistically significantly greater knee excursion during loading for participants with PFPS at 108 hops.min-1 and ankle excursion during loading for healthy participants at maximal efforts, compared to the reference cadence of 132 hops.min-1. Vertical stiffness was significantly lower in the healthy participants at 96 hops.min-1 and maximal efforts when compared to 132 hops.min-1. Compared to hopping at 132 hops.min-1, the lower cadences demonstrated statistically significant differences in spatiotemporal characteristics of hopping, including a greater duration of contact and flight phases and propulsive period in both the PFPS and healthy participant groups. Conclusion: Participants with PFPS had similar movement patterns and mechanical characteristics at the knee and ankle joints compared to matched, healthy, participants. Pain was not provoked in participants with PFPS who had longstanding symptoms, even during repetitive loading at maximal efforts. It is possible that the knee did not flex through enough range during the trials and was not reflective of positions in which knee pain is experienced during functional activities in people with PFPS. The lack of differences between groups may also be reflective of the lack of pain experienced by participants with longstanding PFPS during testing, therefore, not leading to any motor compensations. These findings may guide future studies to examine activities that provoke pain symptoms and mimic the positions in which anterior knee pain is experienced. However, the current study demonstrated that even when there are relatively large forces transmitted though the knee and PFJ during single-leg hopping, which varied from submaximal to maximal efforts, the task may not be sensitive to detect compensatory strategies in people with longstanding PFPS.

Date of Award	2019
Original language	English