Hamstring Injuries
What Is a Hamstring Injury?
A hamstring injury is a strain, partial tear or complete rupture of the hamstring muscle group at the back of the thigh, caused by loading the muscle beyond what it can tolerate. Commonly described as a pulled or torn hamstring, it is frequent in sports that demand sprinting, sudden acceleration, changes of direction and abrupt braking, such as football, athletics, basketball and water skiing. The injury usually happens at the moment the muscle is lengthening rapidly while still generating high force. The large majority of hamstring injuries heal without surgery, with a period of relative rest followed by a structured, progressive loading programme.
Hamstring Anatomy: Three Muscles
The hamstring muscle group lies at the back of the thigh and is made up of three main muscles:
- Biceps femoris: located on the outer-posterior side of the thigh.
- Semitendinosus: sits superficially on the inner-posterior side.
- Semimembranosus: lies on the inner-posterior side, beneath the semitendinosus.
These muscles originate from the sitting bone of the pelvis (the ischial tuberosity), cross both the hip and the knee joint, and attach to the upper part of the lower leg. In this way they bend the knee and extend the hip, drawing the leg backwards. The muscle fibres connect to bone through tendons, and the musculotendinous junction — where muscle meets tendon — is the area most prone to injury.
What Causes It? The Injury Mechanism
Hamstring injuries are fundamentally a problem of overload: the muscle is asked to absorb more force than it can handle. The injury most often occurs during an eccentric contraction, when the muscle is contracting and lengthening at the same time. In the late swing phase of a sprint, as the trailing leg reaches forward, the hamstrings lengthen while producing high force — the moment at which the muscle is most vulnerable. Kicking a ball forcefully, slipping, being pulled forward by the leg while water skiing, or an unexpected deep stretch can tear muscle fibres by the same mechanism.
Who Is at Risk? Risk Factors
The main factors that increase the risk of a hamstring injury are:
- A previous hamstring injury (the strongest single risk factor)
- Limited flexibility and muscle tightness
- Muscle imbalance, with the quadriceps markedly dominant over the hamstrings
- Muscle fatigue and poor conditioning
- Inadequate warm-up and sudden increases in training load
Footballers, sprinters, dancers and water skiers are the groups most often affected. In adolescents going through a growth spurt, bone can lengthen faster than muscle, so the growth plate where the tendon attaches to the sitting bone (the apophysis) may be more vulnerable to strain and to bony avulsion.
Symptoms and Injury Grades
The most characteristic symptom is a sudden, sharp pain at the back of the thigh during running or sprinting. Swelling, tenderness, bruising over the first few days and a loss of muscle strength usually follow. Injuries are graded according to severity:
- Grade 1 (mild): a small number of fibres are strained; pain is mild and settles quickly.
- Grade 2 (moderate): a partial tear, with clear pain, loss of strength and a longer recovery.
- Grade 3 (severe): a complete tear of the muscle or tendon, with marked weakness and sometimes a palpable gap.
In the most severe form the tendon detaches completely from the bone, occasionally pulling a small bone fragment with it. This is called an avulsion injury; it typically occurs near the sitting bone and presents with extensive bruising and pain just below the buttock.
What Can It Be Confused With? (Differential Diagnosis)
Not every pain at the back of the thigh is a hamstring injury. Sciatic pain from a lumbar disc problem, chronic proximal hamstring tendinopathy, bursitis over the sitting bone and pain referred from the hip can all produce a similar picture, so the hip and pelvis need to be assessed as well. When the pain may be arising from joint problems around the knee, the assessment is widened accordingly. One-sided swelling of the leg with increased warmth and tightness in the calf is a warning sign for a blood clot (deep vein thrombosis) and carries its own urgency.
Diagnosis: Examination and Imaging
Diagnosis begins with a detailed history and physical examination. The doctor palpates the painful area, checks whether a gap can be felt, and measures strength and pain with resisted knee flexion and stretch tests. Magnetic resonance imaging (MRI) shows the location of the tear, involvement of the musculotendinous junction and the grade of injury in the greatest detail; ultrasound can help with a dynamic assessment in experienced hands. X-rays do not show soft tissue but are valuable, particularly in adolescents, for detecting a bony avulsion from the growth plate of the sitting bone.
Non-Surgical Treatment
The large majority of hamstring injuries heal with non-surgical care, and this remains the foundation of treatment. In the first days the usual approach is the RICE protocol:
- Rest: pausing the activity that caused the injury.
- Ice: cold application several times a day, for no more than 20 minutes at a time.
- Compression: limiting swelling with an elastic bandage.
- Elevation: keeping the leg above the level of the heart.
As pain and swelling settle, relative rest gives way to controlled, progressive loading. Biological injections such as platelet-rich plasma (PRP) have been studied, but the evidence that they speed up healing in hamstring injuries is inconsistent; these methods are considered on an individual basis in selected cases.
Rehabilitation and Eccentric Strengthening
Rehabilitation is the backbone of hamstring healing and of a safe return to sport. The programme first restores pain-free range of motion and flexibility, then focuses on strengthening the muscle at long lengths through eccentric work. Eccentric exercises — the Nordic hamstring exercise above all — both support healing and reduce the risk of re-injury. As strength returns, running, acceleration and change-of-direction drills are added step by step. Progression should follow the strength and function targets that have actually been reached rather than a fixed calendar.
When Is Surgery Needed?
Most hamstring injuries do not require surgery. It comes into consideration mainly for proximal avulsions, where the tendon has detached completely from the sitting bone, and for complete tears accompanied by marked weakness and retraction, particularly in active patients. In these operations the detached tendon is re-attached to the sitting bone in the hip region using specialised suture anchors. The decision is individual and depends on the type of injury, the amount of retraction, the patient's age and their activity goals.
Recovery and Return to Sport
Recovery time varies with the grade of the injury. Mild strains usually settle within a few weeks, partial tears take longer, and complete ruptures treated surgically may require several months of rehabilitation. Return to sport should be planned not around a fixed date but around meeting defined criteria for strength, flexibility and function. Returning early and under pressure clearly increases the risk of re-injury, and that risk is highest in the first weeks after returning. A criterion-based, staged return programme is therefore essential.
Prevention and When Should You See a Doctor?
Regular eccentric strengthening (especially the Nordic hamstring exercise), balanced training loads, adequate warm-up and flexibility work are effective in preventing hamstring injuries. Pain at the back of the thigh that does not settle within a few days, or that makes walking or everyday movement difficult, should be assessed. Sudden severe pain, a palpable gap, extensive bruising just below the buttock or an inability to bear weight on the leg suggest a severe injury such as an avulsion and require prompt medical assessment. You can find detailed information on other knee problems and contact Assoc. Prof. Serkan Sürücü for an assessment.