Are all hamstring injuries equal? A retrospective analysis of time to return to full training following BAMIC type ‘c’ and T-junction injuries in professional men's rugby union

Brief Summary

Fearghal Kerin, Stuart O’Flanagan, Joe Coyle, Darragh Curley, Garreth Farrell, Ulrik McCarthy Persson, Giuseppe De Vito, Eamonn Delahunt


Hamstring muscle injuries (HMIs) are the most prevalent lower limb muscle injury during participation in field sports. They are also common in many locomotion-based sports and have been described during specific game-related tasks including running, decelerating, kicking and tackling. The prevalence and incidence of HMIs are amplified by their high rate of recurrence. 

The aims of this retrospective study were to:

  • Describe the characteristics of HMIs (injury location, BAMIC grade, time to return to full training, and the rate of re-injury/subsequent injury) 
  • Analyse the influence of intramuscular tendon injury (BAMIC class ‘c’) on the time to return to full training and the rate of re-injury/subsequent injury 
  • Analyse the influence of T-Junction injury on the time to return to full training and the rate of re-injury/sub- sequent injury. 


This retrospective cohort investigation was conducted within a sole European professional men's rugby team. Time lost with HMIs sustained by Leinster Rugby players across 5 competitive seasons (July 2015–June 2021) in 60 players were recorded. All acute HMIs confirmed radiologically through MRI within 5 days of injury, which led to an absence from regular training and match participation exceeding 7 days, were deemed eligible for inclusion.

A total of 143 injuries recorded across 5 competitive seasons were evaluated for eligibility. Out of these, 18 injuries allowed full training in less than 7 days, while in 22 cases, MRI investigation was not conducted. Of the remaining 114 injuries, 23 were subsequently excluded from further analysis. Consequently, 91 HMIs sustained by 46 players throughout the 5 competitive seasons were included for final analysis. Among these, 16 players (18%) encountered two or more HMIs. 


Twenty-six injuries (29%) were proximal, while thirty-seven (41%) were distal. Biceps femoris long head was the most frequently isolated muscle injured (53%), followed by semitendinosus (22%). Grades 1, 2, 3, and 4 accounted for 27, 49, 13, and 2 HMIs respectively. BAMIC ‘b’ was the most common class (n=52, 57%), followed by BAMIC ‘c’ (n=26, 29%), and BAMIC ‘a’ (n=13, 14%). Sixteen of the 26 BAMIC ‘c’ injuries involved partial (n=8) or complete (n=8) loss of tension. Eighteen of 30 distal biceps femoris injuries disrupted the T-Junction. The average time to return to full training was 39.5 days (SD = 38 days; 95% CI = 31–47 days). Ten percent of HMIs re-injured early (<3 months), with 13% re-injuring within 12 months of return. Additionally, 10% of HMIs had a subsequent early injury (<3 months) to the same leg, with 15% having a subsequent injury within 12 months of return. Seven percent suffered a subsequent HMI to the opposite leg within 3 months of return, with 18% experiencing this within 12 months.

Intramuscular Tendon Injury

The median time to return to full training was 18 days (inter-quartile range=14–24days) for the HMIs without intramuscular tendon involvement, and 81days (inter- quartile range = 38–112 days) for the HMIs with intramuscular tendon involvement. This difference was statistically significant for the HMIs that had no intramuscular tendon involvement. There was no statistically significant difference in the rate of re-injury/subsequent injury for HMIs with or without intramuscular tendon involvement.

T Junction Injury

The median time to return to full training was 18 days (inter-quartile range=12–30days) for biceps femoris injuries with no T-junction involvement and 24 days (inter- quartile range=10–44days) for biceps femoris injuries with T-junction involvement. This difference was not statistically significant for the biceps femoris injuries that had no T-junction involvement. There was no statistically significant difference in the rate of re- injury/subsequent injury for biceps femoris injuries with or without T-junction involvement.

This study revealed that rugby players experiencing a hamstring muscle injury (HMI) with intramuscular tendon involvement typically face a longer recovery period, estimated at three times longer than HMIs not involving the intramuscular tendon. While this aligns with prior research, a separate study (Made et al, 2018), where both players and clinicians were unaware of MRI findings, noted only an 8-day disparity in return to full training between HMIs with and without intramuscular tendon involvement. No discrepancy was observed in subsequent HMI rates at 12 months between the two groups. 

T-Junction involvement occurred in 20% of HMIs in this study, a higher rate compared to previous reports (6%). No notable difference in return to full training time or subsequent injury was identified when comparing T-Junction-related biceps femoris injuries to those not involving the T-Junction.

For medical practitioners, these findings emphasise the importance of differential diagnosis and assessment of hamstring injuries when intramuscular tendon involvement and T-Junction injury is suspected. Tailoring the time frame and content of rehabilitation protocols based on the specific injury characteristics is crucial for optimising outcomes and minimising the risk of re-injury.

To this end, having access to KT360 can provide the accurate and reliable strength profiling data necessary for return to high end function and training decisions. The system also provides the ability to accurately progress tendon loads and establish adequate tendon compliance and tolerance prior to undertaking dynamic tasks.

If you would like to learn more about how KangaTech can help your organisation measure strength and mitigate injury risk, please contact