Introduction Patellar tendinopathy (jumper’s knee – pain in the tendon and dysfunction) has a high prevalence, especially in jumping athletes like volleyball players. Excess load on the patellar tendon through high volumes of training and competition is an important risk factor [Visnes, 2014]. Structural changes in the tendon are related with a higher risk of developing patellar tendinopathy [Cook, 2000]. The critical load that affects tendon structure is unknown. The aim of this study was to investigate patellar tendon structure on each day of a five day volleyball tournament in an adolescent population (16–18 years old).
Methods The right patellar tendon of 41 players in the Australian Volleyball Schools Cup (AVSC) was scanned with Ultrasound Tissue Characterisation (UTC) on every day of the tournament (Monday-Friday). UTC can quantify structure of a tendon into four echo-types based on the stability of the echopattern. Hypoechoic abnormalities on grey-scale were also recorded at baseline. Generalised Estimating Equations (GEE) were used to test for change of echo-type I and II over the tournament. Echo-type was used as dependent variable; main effect of time (days of tournament) was determined. In a second analysis the interaction effect time by hypoechoic abnormality was determined.
Results Participants played between 8 and 9 matches during the tournament. Hypoechoic abnormalities were recorded in 14 athletes. There was no significant change in echo-types over the 5 days of the study (echo-type I: Wald χ2 =4.603, df = 4, p = 0.331; echo-type II: Wald χ2 = 6.070, df=4, p = 0.194; see figure 1). Overall echopattern was stable across the tournament in participants without hypoechoic abnormalities while a (non-significant) decrease in echo-type I (less stable echopattern) over time (Wald χ2 = 3.853, df =4, p = 0.426) was seen in athletes with hypoechoic abnormalities (figure 2). Echo-type I was significantly lower in athletes with abnormalities (Wald χ2 = 16.545, df=1, p < 0.001).
Discussion This study shows that patellar tendon structure of 16–18 year old volleyball players is not affected during 5 days of cumulative loading during a volleyball tournament. Subgroups might exist with a different response to load (e.g. existing hypoechoic abnormality). Further research should focus on different loads and subgroups.
References Visnes et al. Scan J Med Sci Sports. 2014;[Epub]
Cook et al. J Ultrasound Med. 2000;19:473–479