Study Design Randomized controlled trial. Objectives To examine the effectiveness of isolated hip abductor and external rotator strengthening on pain, health status, and hip strength in females with patellofemoral pain (PFP). Background Altered hip kinematics resulting from hip muscle weakness has been proposed as a contributing factor in the development of PFP. To date, no study has examined clinical outcomes associated with isolated hip muscle strengthening in those with PFP. Methods Twenty-eight females with PFP were sequentially assigned to an exercise (n = 14) or a no-exercise control group (n = 14). The exercise group completed bilateral hip abductor and external rotator strengthening 3 times per week for 8 weeks. Pain (visual analog scale), health status (WOMAC), and hip strength (handheld dynamometer) were assessed at baseline and postintervention. Pain and health status were also evaluated at 6 months postintervention in the exercise group. Two-factor mixed-model analyses of variance were used to determine the effects of the intervention on each outcome variable. Results Significant group-by-time interactions were observed for each variable of interest. Post hoc testing revealed that pain, health status, and bilateral hip strength improved in the exercise group following the 8-week intervention but did not change in the control group. Improvements in pain and health status were sustained at 6-month follow-up in the exercise group. Conclusion A program of isolated hip abductor and external rotator strengthening was effective in improving pain and health status in females with PFP compared to a no-exercise control group. The incorporation of hip-strengthening exercises should be considered when designing a rehabilitation program for females with PFP. Level of Evidence Therapy, level 2b. J Orthop Sports Phys Ther 2012;42(1):22–29, Epub 25 October 2011. doi:10.2519/jospt.2012.3704

Controlling dynamic interactions between the lower limb and ground is important for skilled locomotion and may influence injury risk in athletes. It is well known that female athletes sustain anterior cruciate ligament (ACL) tears at higher rates than male athletes, and exhibit lower extremity biomechanics thought to increase injury risk during sport maneuvers. The purpose of this study was to examine whether lower extremity dexterity (LED) – the ability to dynamically control endpoint force magnitude and direction as quantified by compressing an unstable spring with the lower limb at submaximal forces – is a potential contributing factor to the “at-risk” movement behavior exhibited by female athletes. We tested this hypothesis by comparing LED-test performance and single-limb drop jump biomechanics between 14 female and 14 male high school soccer players. We found that female athletes exhibited reduced LED-test performance (p=0.001) and higher limb stiffness during landing (p=0.008) calculated on average within 51 ms of foot contact. Females also exhibited higher coactivation at the ankle (p=0.001) and knee (p=0.02) before landing. No sex differences in sagittal plane joint angles and center of mass velocity at foot contact were observed. Collectively, our results raise the possibility that the higher leg stiffness observed in females during landing is an anticipatory behavior due in part to reduced lower extremity dexterity. The reduced lower extremity dexterity and compensatory stiffening strategy may contribute to the heightened risk of ACL injury in this population.

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In this study, we sought to identify sensory circuitry responsible for motor deficits or compensatory adaptations after peripheral nerve cut and repair. Self-reinnervation of the ankle extensor muscles abolishes the stretch reflex and increases ankle yielding during downslope walking, but it remains unknown whether this finding generalizes to other muscle groups and whether muscles become completely deafferented. In decerebrate cats at least 19 wk after nerve cut and repair, we examined the influence of quadriceps (Q) muscles' self-reinnervation on autogenic length feedback, as well as intermuscular length and force feedback, among the primary extensor muscles in the cat hindlimb. Effects of gastrocnemius and soleus self-reinnervation on intermuscular circuitry were also evaluated. We found that autogenic length feedback was lost after Q self-reinnervation, indicating that loss of the stretch reflex appears to be a generalizable consequence of muscle self-reinnervation. However, intermuscular force and length feedback, evoked from self-reinnervated muscles, was preserved in most of the interactions evaluated with similar relative inhibitory or excitatory magnitudes. These data indicate that intermuscular spinal reflex circuitry has the ability to regain functional connectivity, but the restoration is not absolute. Explanations for the recovery of intermuscular feedback are discussed, based on identified mechanisms responsible for lost autogenic length feedback. Functional implications, due to permanent loss of autogenic length feedback and potential for compensatory adaptations from preserved intermuscular feedback, are discussed.