Reliability of Single Limb Squat and Lateral Step Down Assessment in Novice and Expert Clinicians

Abstract

The single limb squat (SLS) and lateral step down (LSD) are common lower extremity tests used to assess gross lower extremity strength and motor control. PURPOSE: To compare intra-rater reliability of lower extremity tests between novice and expert clinicians between sessions. METHODS: Six licensed physical therapists (3 “novice” and 3 “expert”) rated 20 frontal plane video recordings of healthy adults who participated in a previous study performing the SLS and LSD. The sample size required to find a kappa of at least 0.50 with a 95% confidence interval of ±0.40 was estimated to be 18. Novice physical therapists were operationally defined as those within 3 years of initial licensure. Expert physical therapists were licensed for at least 10 years and held a board certification in either orthopedics or sports. Prior to data collection, clinicians practiced rating the SLS and LSD on a separate set of recordings. Kappa statistics were calculated based on previous reported formula and interpreted using a standard index. If bias or prevalence indices were above 0.5, the prevalence-adjusted bias-adjusted kappa (PABAK) was calculated. RESULTS: For the SLS, intra-rater reliability of all raters, except one, had moderate reliability or better. For the LSD, most raters had substantial reliability except for two raters, one novice and one expert, who had fair and moderate reliability, respectively. CONCLUSIONS: Our findings suggest using the SLS to assess lower limb strength and control given its higher reliability in novice and experts. The SLS rating was based on knee movement, while LSD was based on trunk, arm, pelvis, knee, and foot. The higher reliability on SLS than LSD may be due to evaluating only one component rather than several simultaneously.Table 1: Intra-rater reliability of single leg squat and lateral step down test performance by novice and expert raters; kappa (95% confidence interval)