Knee Extensor Dynamics in the Volleyball Approach Jump: The Influence of Patellar Tendinopathy

STUDY DESIGN: Controlled laboratory study using a cross-sectional design. OBJECTIVES: To evaluate knee joint dynamics in elite volleyball players with and without a history of patellar tendinopathy, focusing on mechanical energy absorption and generation. We hypothesized that tendinopathy would be associated with reduced net joint work and net joint power. BACKGROUND: Patellar tendinopathy is a common, debilitating injury affecting competitive volleyball players. METHODS: Thirteen elite male players with and without a history of patellar tendinopathy (mean +/- SD age, 27 +/- 7 years) performed maximum-effort volleyball approach jumps. Sagittal plane knee joint kinematics, kinetics, and energetics were quantified in the lead limb, using data obtained from a force platform and an 8-camera motion analysis system. Vertical ground reaction forces and pelvis vertical velocity at takeoff were examined. Independent sample t tests were used to evaluate group differences (alpha = .05). RESULTS: The tendinopathy group, compared to controls, demonstrated significant reductions (approximately 30%) in net joint work and net joint power during the eccentric phase of the jump, with no differences in the concentric phase. Positiveto-negative net joint work and net joint power ratios were significantly higher in the tendinopathy group, which had a net joint work ratio of 1.00 (95% Cl: 0.77, 1.24) versus 0.76 (95% Cl: 0.64, 0.88) for controls, and a net joint power ratio of 1.62 (95% Cl: 1.15, 2.10) versus 1.00(95% Cl: 0.80, 1.21) for controls. There were no significant differences in net joint moment, angular velocity, or range of motion. Peak vertical ground reaction forces were lower for the tendinopathy group, while average vertical ground reaction forces and pelvis vertical velocity were similar. CONCLUSION: Patellar tendinopathy is associated with differences in sagittal plane mechanical energy absorption at the knee during maximum-effort volleyball approach jumps. Net joint work and net joint power may help define underlying mechanisms, adaptive effects, or rehabilitative strategies for individuals with patellar tendinopathy. J Orthop Sports Phys Ther 2010;40(9):568576. doi:10.2519/jospt.2010.3313