Abstract
BackgroundDynamic knee valgus and internal femoral rotation are proposed to be contributory risk factors for patellofemoral pain and anterior cruciate ligament injuries. Multimodal interventions including hip abductor strengthening or functional motor control programmes have a positive impact of pain, however their effect on knee kinematics and muscle strength is less clear. The aim of this study was to examine the effect of isolated hip abductor strengthening and a functional motor control exercise on knee kinematics and hip abductor strength.MethodsThis prospective, randomised, repeated measures design included 29 asymptomatic volunteers presenting with increase knee valgus and femoral internal rotation. Participants completed either isolated hip abductor strengthening or a functional motor control exercise for 5 weeks. Knee kinematics were measured using inertial sensors during 2 functional activities and hip abductor strength measured using a load cell during isometric hip abduction.ResultsThere were no significant differences in dynamic knee valgus and internal rotation following the isolated hip abductor or functional motor control intervention, and no significant differences between the groups for knee angles. Despite this, the actual magnitude of reduction in valgus was 10° and 5° for the functional motor control group and strengthening group respectively. The actual magnitude of reduction in internal rotation was 9° and 18° for the functional motor control group and strengthening group respectively. Therefore there was a tendency towards clinically significant improvements in knee kinematics in both exercise groups. A statistically significant improvement in hip abductor strength was evident for the functional motor control group (27% increase; p = 0.008) and strengthening group (35% increase; p = 0.009) with no significant difference between the groups being identified (p = 0.475).ConclusionsIsolated hip strengthening and functional motor control exercises resulted in non-statistically significant changes in knee kinematics, however there was a clear trend towards clinically meaningful reductions in valgus and internal rotation. Both groups demonstrated similar significant gains in hip abductor strength suggesting either approach could be used to strengthen the hip abductors.
Highlights
Dynamic knee valgus and internal femoral rotation are proposed to be contributory risk factors for patellofemoral pain and anterior cruciate ligament injuries
Reliability of repeated measurements were excellent for all dependent variables with small Standard error of measurement (SEM) and Minimal detectable change (MDC) values (Table 2) demonstrating good consistency in movement patterns and strength testing
The functional motor control exercise group demonstrated no significant difference in knee valgus or rotation across time for single leg squat or single leg landing
Summary
Dynamic knee valgus and internal femoral rotation are proposed to be contributory risk factors for patellofemoral pain and anterior cruciate ligament injuries. In particular the incidence of patellofemoral pain syndrome (PFPS) has been reported at 8.7% for British Army recruits [2] and 9.7% for anterior cruciate ligament (ACL) injuries during military training [2,3]. The consequences of these injuries are significant, the causes and contributing factors are an important consideration in the prevention of such injuries.
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