Author(s): ZHANG, G., BRINK, M., SZYMSKI, D., HUBER, L., KRUTSCH, W., ALT, V., AUS DER FÜNTEN, K., TROß, T., MEYER, T., LEMMINK, K., HECKSTEDEN, A., Institution: UNIVERSITY MEDICAL CENTER GRONINGEN (UMCG), UNIVERSITY OF GRONINGEN, Country: NETHERLANDS, Abstract-ID: 1860

INTRODUCTION:
Lower-extremity muscle injuries contribute to nearly half of the overall injury burden in professional football, with incidence rates differing across major muscle groups for acute as well as overuse injuries. Importantly, lower-extremity muscle injuries are commonly associated with an increased susceptibility to subsequent injury especially in the weeks after return-to-play (RTP). However, the post-RTP risk trajectories following different lower-extremity muscle injuries remain insufficiently characterised. This descriptive study aimed to investigate the risk trajectories for non-contact subsequent injury after returning from major lower-extremity muscle injuries in professional football, differentiating acute from overuse index injuries.
METHODS:
Prospectively collected injury data from clubs in 1st and 2nd German Bundesliga over three seasons (2022/23 to 2024/25) were used for time-to-event analysis. Index injuries (i.e., injuries from which players returned to play) of interest included muscle injuries to hamstrings, quadriceps, adductors, and calf. Acute and overuse index muscle injuries were analysed separately across these locations. Non-contact time-loss subsequent injuries were considered as the event of interest. Built upon previously published methodology [1], the Kaplan-Meier survival function was used to estimate the cumulative hazard function, from which the continuous hazard function was derived.
RESULTS:
Over the three seasons, 374 acute and 304 overuse index injuries were identified at the four lower-extremity muscle groups. Observed subsequent-injury rates were hamstring 27.9%, quadriceps 26.2%, adductor 39.3%, and calf 21.2% for acute index injuries, and hamstring 28.1%, quadriceps 27.7%, adductor 27.2%, and calf 27.4% for overuse index injuries. While the time course of subsequent injury risk globally aligned with previous findings, differences between muscle groups were observed. Players returning from acute hamstring and adductor injuries showed elevated risk which diminished within approximately twelve and four weeks, respectively, and levelled off thereafter. By contrast, a delayed risk peak around three weeks after RTP was found for overuse calf index injuries.
CONCLUSION:
This descriptive study characterised the time-varying nature of subsequent injury risk for specific lower-extremity muscle injuries. The observed differences in risk trajectories across muscle groups highlighted the need for careful RTP decision-making based on each index injury.

References
1. Zhang G, Brink M, Tröß T, et al. The time course of injury risk after return-to-play in professional football (soccer). Sports Medicine. 2024:1-9.