Abstract

Objective: The etiology of patellar tendinopathy (jumper's knee) remains unclear. In order to see if landing strategy might be a risk factor for the development of this injury, this study examined whether landing dynamics from drop jumps differed amongst healthy volleyball players (CON) and volleyball players with a jumper's knee. The jumper's knee patients were divided into an asymptomatic group with a previous jumper's knee (PJK) and a symptomatic group with a recent jumper's knee (RJK).

Methods: Inverse dynamics analyses were used to estimate lower extremity joint dynamics from 30, 50 and 70 cm drop jumps in the three groups (CON n=8; PJK n=7; RJK n=9). A univariate repeated measures ANOVA analysis was used to compare the different landing techniques.

Results: Data analysis of the landing dynamics revealed that PJK showed higher knee angular velocities (p<.01), strong tendencies of higher loading rate of VGRF (p=.05) and higher knee extensor moment loading rate (p=.08), and higher ankle plantar flexion moment loading rate (p<.01) compared to CON. Higher values for peak knee moment, peak knee power and knee work (all p<.01) were found for CON compared to RJK. The comparison of the two jumper's knee groups yielded higher knee angular velocities (p<.01), together with higher ankle plantar flexion and knee extensor moment loading rate (p<.01, p<.05 respectively).

Conclusion: Where RJK used a landing technique to avoid high patellar tendon loading, PJK used a stiffer landing strategy, which may be a risk factor in the development of patellar tendinopathy.