How common are hamstring strain injuries?
Hamstring strains are one of the most common soft tissue injuries seen in sport and everyday activity. This is particularly evident in field-based sports involving sprinting, such as Gaelic football, soccer and rugby where hamstring strain injuries make up 15-24% of all injuries (Roe et al. 2018; Chavarro-Nieto et al. 2023; Ekstrand et al. 2023).
How hamstring injury occurs?
Hamstring strains are most commonly the result of high-speed running, particularly in the terminal swing phase of running (Schache et al. 2009). However, other mechanisms of injury exist and include decelerating, kicking, tackling and stretch related injuries (Danielsson et al. 2020; Kerin et al. 2022).
The hamstrings are bi-articular muscles which mean they cross two joints, the hip and knee. This means that the hamstrings are responsible for movements at the hip and the knee (i.e knee flexion, hip extension, and tibial internal and external rotation). There are 3 hamstring muscles, the biceps femoris, semimembranosus and semitendinosus. The biceps femoris muscle accounts for 83% of all hamstring strain injuries (Ekstrand et al. 2023).
Are there different types of hamstring injury?
Hamstring strain injury involves tearing or overstretching of the muscle fibres of one of the hamstring muscles. They are graded depending on the severity of the tear which give us an idea of how long the injury will take to recover and how long rehabilitation will take. The most up to date grading system is the British athletic muscle injury classification (BAMIC) system. This system uses MRI to grade injuries, using a numerical scale (0-4) t indicate the severity of the injury and letter classification (a, b, c) to indicate the anatomical site injured.
1. Grading (Severity of Injury)
The numerical grade (0–4) indicates how much structural damage there is:
- Grade 0: No MRI evidence of muscle injury (may be muscle soreness or delayed onset muscle soreness).
- Grade 1: Small injury, involving minimal structural damage. Typically affects a few muscle fibres with little or no loss of strength.
- Grade 2: Moderate injury involving partial tear of the muscle with more extensive fibre disruption.
- Grade 3: Extensive partial tear with significant loss of muscle fibres, often seen as a gap on MRI.
- Grade 4: Complete muscle or tendon rupture.
2. Letter Classification (Anatomical Site of Injury)
The letter (a, b, or c) describes where in the muscle-tendon unit the injury occurs:
- a – Myofascial injury: Involves the muscle belly or fascia (outer connective tissue).
- b – Musculotendinous junction injury: Occurs where the muscle fibres join the tendon (most common site). Takes a little longer than an injury to heal.
- c – Intratendinous injury: Involves the tendon itself; typically, more severe with longer rehabilitation time than a or b injuries.
What can physiotherapy do to help?
Hamstring Rehabilitation is guided by the severity of the injury and the individual’s activity level. The main goals are to restore flexibility, strength, and control, while gradually reintroducing sport-specific/functional movements. Physiotherapists will design a structured program that progresses through the following stages which are not independent to each other:
Early Phase: After an initial 48 hours of rest, we can start to load the injured tissue. The aims of the early phase are to regain mobility and early loading to optimise tissue remodelling.
Strengthening Phase: Gradual introduction of progressive hamstring strengthening exercises, particularly eccentric (lengthening) contractions that are both hip and knee dominant, which are vital for recovery and reduce risk of re-injury. The aim of this phase restores equal strength in both legs.
Return-to-Sport Phase: Progressive sprinting, agility, and sport-specific training to ensure full readiness to return to play and reduce risk of re-injury. (Sports Injuries)
Take home message
With early assessment and a structured rehabilitation plan, hamstring strains recover fully. However, rushing the process or neglecting key aspects of rehab can lead to recurrence. If you suspect a hamstring injury, seek advice from your chartered physiotherapist for an accurate diagnosis and tailored treatment plan. BOOK NOW
Oisin Kelly BSc, MSc (Sports Medicine) recently completed a masters in sports medicine at TCD, his thesis investigated “The reliability and muscle activity of hamstring strength tests” (Meet the Team)
References:
Chavarro-Nieto C, Beaven M, Gill N & Hébert-Losier K. (2023). Hamstrings injury incidence, risk factors, and prevention in Rugby Union players: a systematic review. Phys Sportsmed 51, 1-19.
Danielsson A, Horvath A, Senorski C, Alentorn-Geli E, Garrett WE, Cugat R, Samuelsson K & Hamrin Senorski E. (2020). The mechanism of hamstring injuries – a systematic review. BMC Musculoskelet Disord 21, 641.
Ekstrand J, Bengtsson H, Waldén M, Davison M, Khan KM & Hägglund M. (2023). Hamstring injury rates have increased during recent seasons and now constitute 24% of all injuries in men’s professional football: the UEFA Elite Club Injury Study from 2001/02 to 2021/22. British Journal of Sports Medicine 57, 292-298.
Kalkhoven JT, Lukauskis-Carvajal M, Sides DL, McLean BD & Watsford ML. (2023). A Conceptual Exploration of Hamstring Muscle-Tendon Functioning during the Late-Swing Phase of Sprinting: The Importance of Evidence-Based Hamstring Training Frameworks. Sports Med 53, 2321-2346.
Kerin F, Farrell G, Tierney P, McCarthy Persson U, De Vito G & Delahunt E. (2022). Its not all about sprinting: mechanisms of acute hamstring strain injuries in professional male rugby union-a systematic visual video analysis. Br J Sports Med 56, 608-615.
Roe M, Murphy JC, Gissane C & Blake C. (2018). Hamstring injuries in elite Gaelic football: an 8-year investigation to identify injury rates, time-loss patterns and players at increased risk. Br J Sports Med 52, 982-988.
Schache AG, Wrigley TV, Baker R & Pandy MG. (2009). Biomechanical response to hamstring muscle strain injury. Gait Posture 29, 332-338.