Evidence for Reliability and Validity of Functional Performance Testing in the Evaluation of Nonarthritic Hip Pain

Abstract

Context The single-legged–squat test (SLST) and step-down test (SDT) are 2 functional performance tests commonly used to evaluate active people with nonarthritic hip pain and dysfunction. However, evidence to support the use of the SLST and SDT in this population is lacking. Objective To offer evidence of reliability and validity for the SLST and SDT in evaluating patients with nonarthritic hip pain. Design Cross-sectional study. Setting Orthopaedic surgeon's clinical office. Patients or Other Participants Forty-five patients (27 female and 18 male participants; age = 28.5 ± 10 years, height = 171.6 ± 10.1 cm, weight = 73.9 ± 15.2 kg, and body mass index = 25 ± 4.1) diagnosed with nonarthritic hip pain. Main Outcome Measure(s) Participants performed the SLST and SDT. Interrater reliability and validity of passive internal rotation of the hip, visual analog scale (VAS) scores, and hip outcome scores (HOSs) for limitations in activities of daily living and sport-related activities (SRAs) were collected. Results Interrater reliability was moderate to excellent for both the SLST (0.603–0.939) and SDT (0.745–0.943). Participants who passed or failed the SLST and SDT differed on the following measures: VAS for the SLST (F1,43 = 16.21, P < .001); VAS for the SDT (F1,43 = 13.41, P = .001); HOS-activities of daily living for the SLST (F1,40 = 5.15, P = .029); HOS-SRAs for the SLST (F1,40 = 7.48, P = .009); and HOS-SRAs for the SDT (F1,40 = 6.42, P = .015). Conclusions Our study offers evidence for the use of the SLST and SDT as reliable and valid functional performance tests in the evaluation of physical function for patients with nonarthritic hip pain.