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

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. To evaluate the influence of physical characteristics and use of a decline board on squat performance in a hip pain population. Cross-sectional study setting. Clinical Patients: In total, 33 individuals scheduled for arthroscopic hip surgery were matched with 33 healthy controls. Hip and ankle ROM, hip strength, and trunk endurance were assessed, along with knee and trunk kinematics during squat on flat and 25° decline surfaces. 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. 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 trunk (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. 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.