Reliability And Validity Of Dynamic Frontal Plane Motion Visual Assessments During A Lateral Step Down

Abstract

Quantitative assessment of dynamic frontal plane knee motion has been reported to be reliable and valid in a female population. Research investigating the qualitative assessment is limited and small in numbers. PURPOSE: To test the inter- and intra-tester reliability and validity of a qualitative assessment of frontal plane knee motion during a lateral step down. METHODS: Twenty-four men (age=23.7±4.6 years, height=180.7±6.6 cm, weight=86.9±4.8 kg) and thirty women (age = 22.7±4.7 years, height = 168.7±6.9 cm, weight = 66.7±15.4 kg) who self-reported as healthy, active, and free from lower extremity pain/injury participated. Five lateral step-downs were recorded using a video camera and 3D motion capture system on two separate testing dates. Images and knee frontal plane angles were extracted from the video and 3D motion analysis data, respectively, at standing and maximum knee flexion. Two testers observed the videos and images to classify the movement as dynamic valgus (>10°), no change (-10 to 10), or dynamic valgus (<-10°). The classification was based on the estimated change in frontal plane projection angle (FPPA) of the knee from single-legged stance to maximum knee flexion. The FPPA and actual change values were calculated separately. Kappa (κ) values were used to determine reliability and construct validity. RESULTS: A total of 274 videos were analyzed. The intratester reliability was κ=0.724 (women [w]: 0.766, men [m]: 0.642) for tester one and κ=0.626 (w: 0.654, m: 0.581) for tester two. The intertester reliability was κ=0.481 (w: 0.554, m: 0.370) on day one and κ=0.505 (w: 0.473, m: 0.529) on day two. Compared to FPPA, visual assessment resulted in κ=0.602 (w: 0.635, m: 0.475), κ=0.371 (w: 0.497, m: 0.190), κ=0.516 (w: 0.698, m:0.153), κ=0.364 (w: 0.455, m: 0.155) for testers one and two, respectively, on days one and two, respectively. CONCLUSIONS: This study is the first to test reliability and validity in a large sample of men and women. Reliability was fair to substantial and agreement with FPPA was slight to moderate. Results were typically better in women because they rarely demonstrated dynamic varus. Use of visual assessment in the categorization of dynamic frontal plane motion is questionable, especially in a male population.