Single-Leg Squat as a Tool to Evaluate Young Athletes' Frontal Plane Knee Control

Objective: To determine the agreement between 2-dimensional video analysis and subjective visual assessment by a physiotherapist in evaluating young athletes' knee control, and to determine the intra-rater reliability and inter-rater reliability of the single-leg squat test. Design: Frontal plane knee control was assessed by a physiotherapist on a 3-point scale. Frontal plane projection angles were calculated from video images. To determine the intrarater reliability, a physiotherapist reassessed 60 subjects' performances from a video. For the inter-rater reliability, 20 subjects were assessed by both the physiotherapist and a nonexperienced tester. The study continued for 3 test years. Setting: Research institute. Participants: Three hundred and seventy-eight floorball, basketball, ice hockey, and volleyball players. Assessment of Variables: Knee control was assessed to be good, reduced, or poor. Main Outcome Measures: Agreement between the video analysis and subjectively assessed frontal plane knee control. Intrarater reliability and inter-rater reliability. Results: There were statistically significant differences in the mean frontal plane knee angles between subjects rated as having "good," "reduced," or "poor" knee control. Intrarater reliability was fair for the assessments in the first year, moderate (dominant leg) and good (nondominant leg) for the second year, and very good (dominant leg) and good (nondominant leg) for the third year. Inter-rater reliability was fair/poor. Conclusions: This study suggests that by using the subjective assessment of the single-leg squat task, it is possible to detect differences in frontal plane knee control in young team sport athletes. The assessment can be considered to be reliable for clinical use when performed by an experienced tester.