Reliability and criterion validity of two-dimensional movement assessments in those with patellofemoral pain

Determine criterion validity and intra/inter-rater reliability of 2-dimensional (2D) knee frontal plane projection angle (kFPPA), hip frontal plane projection angle (hFPPA), and dynamic valgus index (DVI) during forward step-downs in those with patellofemoral pain (PFP). Cross-sectional. University research laboratory. 39 participants with PFP (34.18 ± 7.41years, 170± .1 cm, 81.03 ± 19.36 kg, duration of pain: 68.67 ± 85.08months, anterior knee pain scale: 80.49 ± 7.87, visual analog scale:2.08 ± 2.02) Average 3D hip and knee sagittal, frontal, and transverse joint angles and 2D kFPPA, hFPPA, and DVI at maximum knee flexion were variables of interest. 3D DVI was calculated as the sum of hip and knee frontal and transverse angles. 2D kFPPA, hFPPA, and DVI were calculated by two raters independently on two occasions. Intra- and inter-rater reliability of all 2D angles were excellent. kFPPA was moderately correlated to 3D knee transverse angles. hFPPA was moderately correlated to 3D hip frontal and transverse angles and largely correlated to 3D DVI. 2D DVI was moderately correlated to hip transverse angles. kFPPA, hFPPA, and DVI are reliable. hFPPA may be reflective of 3D hip and knee frontal and transverse motion during forward step-downs in those with PFP. •kFPPA, hFPPA, and DVI have excellent between and within clinician reliability. .•hFPPA may be an alternative to hip and knee 3D frontal and transverse angles.•Correlation coefficients were strong when hFPPA was compared to 3D DVI.