REDUCTION IN PATELLOFEMORAL PAIN IS ASSOCIATED WITH INCREASES IN CONTACT AREA FOLLOWING PATELLAR BRACING

Abstract

Elevated patellofemoral joint stress (force/unit area) as a result of patellar malalignment has been hypothesized as being contributory to patellofemoral pain. Clinically, bracing has been reported to decrease patellofemoral pain, however studies have shown minimal or no changes in patellar alignment. It is our hypothesis that decreases in pain are associated with increases in patellofemoral contact area, as forces would be distributed over a larger surface area. PURPOSE: To evaluate the relationship between changes in patellofemoral pain and changes in patellofemoral joint contact area. METHODS: Seven females (age: 31 ± 8y; height: 165 ± 9cm; body mass: 56 ± 6kg) with readily reproducible pain participated in this study. Subjects were first asked to rate their pain during a unilateral squat using a visual analog scale. A patellofemoral joint brace was then applied and the unilateral squat and visual analog scale pain rating was repeated. Following the pain assessment, magnetic resonance imaging was conducted while performing isometric contractions against 25% body weight at 0, 20, 40, & 60 degrees of knee flexion. This was repeated for both braced and non-braced conditions. Using a previously established protocol, measurements of patellofemoral joint contact area were made using NIH imaging software. Pearson's correlation coefficients were used to quantify the relationship between changes in contact area and changes in patellofemoral pain. RESULTS: On the average, subjects reported a 40% decrease in pain following bracing. Significant increases in contact area were observed in the braced condition across all knee flexion angles evaluated. Decreases in patellofemoral pain were found to be significantly associated with increases in contact area at 0° (r = .42), 20° (r = .69), and at 40° (r = .56.) CONCLUSION: These results indicate that increases in contact area may contribute to decreased symptoms in persons with patellofemoral pain. The compression imparted to the patellofemoral joint as a result of bracing likely seats the patella more firmly in the trochlear groove, thereby distributing joint reaction forces over a greater surface area (ie. decreased stress.) These findings support the use of patellofemoral bracing as an intervention to reduce patellofemoral pain. Supported by the unrestricted grant from Don Joy, Inc.