Objective: The aetiology of patellar tendinopathy (jumper's knee) remains unclear. To see whether landing strategy might be a risk factor for the development of this injury, this study examined whether landing dynamics from drop jumps differed among healthy volleyball players (CON) and volleyball players with a jumper's knee. The patients with jumper's knee 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 analysis of variance was used to compare the different landing techniques. Results: Data analysis of the landing dynamics revealed that PJK showed higher knee angular velocities (p,0.01), and higher ankle plantar flexion moment loading rate (p,0.01). Furthermore, strong tendencies of higher loading rate of vertical ground reaction force (p = 0.05) and higher knee extensor moment loading rate (p = 0.08) were found compared with CON. Higher values for peak knee moment, peak knee power and knee work (all p,0.01) were found for CON compared with RJK. The comparison of the two jumper's knee groups yielded higher knee angular velocities (p,0.01), together with higher ankle plantar flexion and knee extensor moment loading rate (p,0.01 and p,0.05, 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. P atellar tendinopathy (jumper's knee) is the most common injury among volleyball players, with a prevalence between 40% and 50% among elite players.1 2 In many cases, this injury causes a reduction in playing level and a long interruption of training and competition. The high prevalence induces further research to focus on the underlying mechanism that plays a role in the aetiology of patellar tendinopathy, to develop suitable preventive strategies.3 Patellar tendinopathy originates from repetitive loads exposed to the quadriceps extensor mechanism (eg, patellar tendon) during the jump-landing sequence. After cumulative microtrauma, degenerative changes of the tendon can take place.
4Factors such as training volume and floor type were associated with the incidence of patellar tendinopathy. 5 The latter was in line with a lower prevalence in elite beach volleyball players, who play on soft sandy undergrounds. 6 Female elite athletes are twice less vulnerable to patellar tendinopathy than their male counterparts, 2 7 which might be caused by the fact that women in general generate less power. Furthermore, the demonstration that patients with jumper's knee show better jumping ability and power generation than healthy players suggests that volleyball players with a jumper's knee subject their quadriceps extensor mechanism to higher loads.
