Hamstring injuries are more common than ever

A recent study published in the British Journal of Sports Medicine suggested hamstring injuries are increasing both in number and the burden of injury in a late European football.

The UEFA Elite Club Injury Study (ECIS) has for more than 20 years evaluated the risk of injury for top-level men’s soccer leagues in Europe. Led by Jan Ekstrand, it is surely the outstanding ongoing research project related to injuries in elite sport.

The ECIS has previously published data on the incidence of hamstring injuries, labelling them “the most common injury in football”, comprising 12-17% of all time-loss injuries in male professional football. Recently the group has updated its data and now has data from 21 seasons. This study added the last eight seasons to the previous work.

During the 2001/02 to 2021/22 seasons, team medical staff reported 2636 hamstring injuries during 2131561 total expo-sure hours; 922 injuries (34%) during 1787823 training hours and 1714 injuries (66%) during 343738 match hours. The proportion of reported injuries that were diagnosed as hamstring injuries increased from 12% in the first season to 24% in the last season and constituted 19% of all 14057 injuries registered during the 21-season study period. In terms of absence days, hamstring injuries caused 14% of the total injury lay-off days, increasing from 10% to 20% between the 2001/02 and the 2021/22 seasons.

The median lay-off following a hamstring injury was 13 days (IQR 7–22). In general, 20% of players missed training or match play due to hamstring injury during a season, and a 25-player squad can expect about eight hamstring injuries per season. Of all the hamstring injuries, 475 (18%) were recurrences, and early recurrences (within 2months, n=325) made up 69% of these

In the period 2014/15 to 2021/22, time trend analysis revealed a significant increase in both training hamstring injury incidence and training hamstring injury burden. Almost 50% of match hamstring injuries occurred during the last 15min of the first and second halves, which deviated from the expected match distribution

Of the 1843 injuries reported since the 2011/12 season, 1319 (72%) were given diagnoses specific to either biceps femoris or semitendinosus/semimembranosus. Biceps femoris injuries (n=1054, 80%) were more common, especially in match play (n=761, 84%). a significant overall difference in the frequency of injury mechanisms between biceps femoris and semitendinosus/semimembranosus injuries (p=0.009), with a higher proportion of lateral injuries caused by running/sprinting while fewer lateral injuries were caused by stretching. Lateral injuries were also associated with longer absence than medial injuries (p=0.010) with a larger proportion of the medial inju- ries being minimal or mild (p=0.009).

• The most important findings were that the proportion of all injuries diagnosed as hamstring injuries increased from 12% to 24%, and that the proportion of all injury absence days caused by hamstring injuries increased from 10% to 20% during the 21-year study period.
• The most worrying finding was that the injury rates have increased during the recent eight seasons.
• The most surprising finding was that structural injuries were more common than functional injuries during the most recent 11 seasons.
• The most expected findings (extending previous studies) were that hamstring injuries were: (1) most commonly due to running/sprinting; (2) more likely to occur in the last 15min of match halves; (3) affect the biceps femoris rather than the semimembranosus/semitendinosus muscles; and (4) predisposed to recur within 2 months in the same location.

The authors propose two possible explanations for the increase –  the increased intensity of elite mens football, and the increase in the total amount of international team travel and matches .

They also ask why are the hamstring injury rates not decreasing despite studies showing the the Nordic Hamstring Exercise can reduce injury rates by 65-70%. They note that the programme has not been widely adopted in men’s professional football in Europe.

Challenges to implementing the programme include:

• limited influence by the medical team on coaching practices
• limited time to include preventive exercises in training before a match
• players indicating that the exercise gives them muscle soreness

As for suggestions on what can be done to reduce the burden of hamstring injuries, the authors suggest collaboration between medical staff, coaches, players and directors will provide the best perspective of how the game of football evolves. Such interdisciplinary discussion is likely to help find solutions to keep players safe and at reduced injury risk . Noting the high incidence of recurrence, they recommend that clinicians discuss this crucial point with players and coaches/managers/‘the football department’ so that appropriate programmes can be implemented .

Ekstrand J, et al. Br J Sports Med 2023;57:292–298. doi:10.1136/bjsports-2021-105407

This study and others will be included in the hamstring chapter of the 6^th edition of Clinical Sports Medicine currently “under construction”. We really value your input so if you have any suggestions at all regarding possible changes to the hamstring chapter (Chapter 34 – Posterior Thigh Pain) from the 5^th edition, please add your comments here.