Frontal plane projection angle predicts patellofemoral pain: Prospective study in male military cadets.

BACKGROUND: Patellofemoral pain (PFP) is a major source of knee pain. Identifying who may develop PFP is of paramount importance. PURPOSE: To assess whether Frontal plane projection angles (FPPA) and hand held dynamometry (HHD) strength measures can predict development of PFP. STUDY DESIGN: Prospective evaluation of individuals undertaking a military training programme. METHODS: Male military recruits were enrolled and prospectively followed up from enrolment to completion of 12-weeks training. Lower limb kinematics (FPPA, Q-angle, hip adduction angle, knee flexion, ankle dorsiflexion, and rearfoot eversion angle) measured during running, single leg squatting (SLS), and single leg landing (SLL) and isometric muscle strength of hip abductors and knee extensors. RESULTS: Body mass, hip abductor muscle strength, Q-angle during SLS and SLL, FPPA during SLL all significantly different between the PFP and non-injured groups and predicted PFP, highest predictor variable was FPPA during SLL (Odds Ratio = 1.13, P = 0.01). A FPPA≥5.2° during SLL predicting PFP with a sensitivity of 70% and a specificity of 70%. CONCLUSION: Participants who developed PFP had a number of physical factors significantly different than the non-injured group, most predictive was a larger FPPA during SLL, with angles greater than 5.2° associated with a 2.2x greater risk. CLINICAL RELEVANCE: Assessing FPPA during SLL could be used to determine who was predisposed to PFP.