Changes in Knee and Trunk Alignment in People With Hip Pain and Healthy Controls When Using a Decline Board During Single-Leg Squat

Context: Hip pain is associated with reduced hip muscle strength. range of movement (ROM), and decreased postural stability. Single-leg squat is a reliable and valid method to measure dynamic balance. Objective: To evaluate the influence of physical characteristics and use of a decline board on squat performance in a hip pain population. Design: Cross-sectional study setting. Clinical Patients: In total, 33 individuals scheduled for arthroscopic hip surgery were matched with 33 healthy controls. Interventions: Hip and ankle ROM, hip strength, and trunk endurance were assessed, along with knee and trunk kinematics during squat on flat and 25 degrees decline surfaces. Main Outcome Measures: Between-group and surface differences in alignment, between-group strength and ROM. and associations between alignment and physical characteristics were assessed and determined using mixed model analysis of variance and Pearson R. Results: The hip pain group had significantly less strength and ROM for all directions except abduction strength and ankle dorsiflexion (P > .02). No differences existed between the 2 groups for mink (P < .70) or knee displacement (P < .46) during squat on either surface. When the 2 groups were combined (n = 66), decline squat significantly reduced knee medial displacement in both limbs by approximately 1 cm (P < .01). Decline squat reduced trunk lateral movement on 1 side only (P= .03). Reduced knee displacement during decline squat showed fair association with less hip-extension strength (r= -.29), hip-flexion strength (r= -.25), and less dorsiflexion (r= -.24). Strength and range were not associated with trunk displacement. Conclusions: Decline squat reduced medial knee and lateral trunk displacement regardless of hip pain. Reductions may be greater in those with lesser hip muscle strength and dorsiflexion. Use of a decline board during squat for improving knee and trunk alignment should be considered as a goal of exercise intervention.