Classification of lower extremity movement patterns based on visual assessment: reliability and correlation with 2-dimensional video analysis

Abstract

Context: Abnormal movement patterns have been implicated in lower extremity injury. Reliable, valid, and easily implemented assessment methods are needed to examine existing musculoskeletal disorders and investigate predictive factors for lower extremity injury.

Objective: To determine the reliability of experienced and novice testers in making visual assessments of lower extremity movement patterns and to characterize the construct validity of the visual assessments.

Design: Cross-sectional study.

Setting: University athletic department and research laboratory.

Patients or other participants: Convenience sample of 30 undergraduate and graduate students who regularly participate in athletics (age = 19.3 ± 4.5 years). Testers were 2 experienced physical therapists and 1 novice postdoctoral fellow (nonclinician).

Main outcome measure(s): We took videos of 30 athletes performing the single-legged squat. Three testers observed the videos on 2 occasions and classified the lower extremity movement as dynamic valgus, no change, or dynamic varus. The classification was based on the estimated change in frontal-plane projection angle (FPPA) of the knee from single-legged stance to maximum single-legged squat depth. The actual FPPA change was measured quantitatively. We used percentage agreement and weighted κ to examine tester reliability and to determine construct validity of the visual assessment.

Results: The κ values for intratester and intertester reliability ranged from 0.75 to 0.90, indicating substantial to excellent reliability. Percentage agreement between the visual assessment and the quantitative FPPA change category was 90%, with a κ value of 0.85.

Conclusions: Visual assessments were made reliably by experienced and novice testers. Additionally, movement-pattern categories based on visual assessments were in excellent agreement with objective methods to measure FPPA change. Therefore, visual assessments can be used in the clinic to assess movement patterns associated with musculoskeletal disorders and in large epidemiologic studies to assess the association between lower extremity movement patterns and musculoskeletal injury.

Keywords: athletic injuries; knee valgus; movement analysis; screening.

Figures

Figure.

Methods for objective measurement of the frontal-plane projection-angle (FPPA) change. We drew 2 lines to represent the FPPA: 1 bisected the thigh segment, and 1 bisected the lower leg. The angles were then measured using a protractor function in the measurement software. The FPPA change was calculated by subtracting the ending FPPA from the starting FPPA. Representative examples of the 3 lower extremity movement classifications are shown. A, Dynamic valgus: angle between the femoral bisection and lower leg bisection changed more than 10°, and the knee moved toward the midline of the body. B, No change: angle between the femoral bisection, and lower leg bisection changed less than 10° during the motion. C, Dynamic varus: angle between the femoral bisection and lower leg bisection changed more than 10°, and the knee moved away from the midline of the body.