Squatting in adolescents with unilateral and bilateral hip dysplasia.

Background: Adolescent hip dysplasia is a condition that often affects hip mechanics, leading to loss of function, pain, and early onset osteoarthritis. Objective literature investigating functional activities remains sparse within this population. A traditional body weight deep squat has translation to everyday tasks, is a clinical screening tool, and is also a common pre/rehabilitation exercise. However, the biomechanical approach and potential movement compensations have not been investigated in this population.

Methods: Thirty patients diagnosed with dysplasia from a pediatric hip registry were included. Each patient completed 3D motion capture with minimal instructions during the squat. Wilcoxon signed-rank tests were conducted to compare differences between: affected and unaffected limbs, unilateral and bilateral patients, patients and controls. A Spearman correlation assessed the relationship between symptom severity (modified Harris Hip Score) and squat depth.

Findings: Unilateral and bilateral patients demonstrated similar biomechanical movement patterns across both limbs (p > 0.05). When compared to controls, dysplasia patients squatted with less sagittal plane range of motion throughout the lower extremities, reducing achievable squat depth (p < 0.05). Upright trunk positioning was identified as a movement compensation that led to a reduction in the hip flexor moment. Symptom severity was not associated with squat depth (r = -0.282, p = 0.058).

Interpretation: An upright trunk compensation (i.e. knee dominant squat) may be utilized by adolescent hip dysplasia patients. When incorporating squats for targeted hip strengthening in this population, it may be advisable for clinicians to encourage greater trunk flexion to effectively engage the hip musculature.