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Hamstring Injury: Causes, Symptoms, Risk factors, Complications, Treatment and Prevention

The hamstring is a large muscle at the back of the thigh. It helps in bending of the leg at the knee joint. Hamstring injury (aka hamstring strain) is a common leg injury in athletes.

Some of the common symptoms of hamstring injury include severe pain at the back of the thigh and difficulty in performing movements like bending at the knee. Treatment mainly consists of rest and icing. Surgery is rarely considered for treatment.

Hamstring injury

What is Hamstrings Injury?

A pull or an injury to the muscle on the back of the thigh is called a hamstring injury. Hamstring is a bulky muscle, which extends from the buttocks to the knee joint on the back side of the thigh. It is responsible for straightening the leg at the hip and bending of the knee.

Hamstring muscle strain is categorized into different grades, they are:

  • Grade-1: A mild muscle pull or strain
  • Grade-2: A partial muscle tear
  • Grade-3: A complete muscle tear

The time for recovery from a hamstring injury depends on the grade of injury. Grade 1 injury heals rapidly, but other grades (grade 2 and 3) of injuries may recover gradually (few weeks or months of time).

In severe cases of hamstrings injury, the muscle tears entirely and pulls along a piece of bone with them. Such injuries are called avulsion injuries.

What Causes Hamstring Injury?

Hamstring injury mainly occurs due to overstretching of the muscles in specific activities like running and jumping. Some of the common factors that cause hamstring strain include:

  • Sudden increase in muscle load: Sudden overloading of the hamstring muscle during sports activities like sprinting (running for a short distance for a limited time to reach the target).
  • Sports injuries: Overstretching of the muscles while playing certain sports like football.
  • Traumatic events: Any severe injury to the spine or hip joints during accidents.

What are the Risk Factors for Hamstring Injury?

Several factors can increase the risk of hamstring muscle injury. Some of them are listed below:

  • Age: Hamstring injury is commonly seen in older patients, because the muscles tend to weaken with ages. This weakness can be due to underlying conditions like the osteoarthritis of the knee. The risk of occurrence of hamstring injuries increases with weaker hamstrings muscle.
  • Weak muscles: A weak muscle is more prone to injuries. Hamstrings muscle may become weak, if it did not recover completely from a previous hamstring strain.
  • Muscle tightness: No regular warm-up or stretching exercises, sets in muscle tightness, in sports players. Tightness of muscles makes them less efficient and more prone to injuries.
  • Muscle imbalance: The knee joint is surrounded by two major muscle groups, quadriceps, at the front of the thigh and hamstrings, at the back of the thigh. These muscle groups work in coordination to allow for the normal movements in the knee joint. If one group of muscles is weaker than the other group, this increases the risk of injury to the weakened muscles. In knee joint, usually the quadriceps is stronger than the hamstrings muscle and this makes the hamstrings more susceptible to injuries.
  • Muscle fatigue: Repeated, continuous and strenuous physical activities involving the knees makes the hamstrings extremely fatigued. This reduces the efficiency of the muscle to perform strenuous physical activity and makes it prone to injury.
  • Sports activities: Sports like running and basketball involve sudden jumps and high pressure on the legs and make them prone to muscle injuries.

What are the Complications of Hamstring Injury?

Complications associated with hamstring injury vary, depending on their onset (early or late onset of complications). Some of the common complications include:

  • Deep vein thrombosis: Damage to the hamstrings muscle owing to trauma may also lead to the formation of a blood clot in the leg. This clot may impede the circulation in the veins supplying lower legs and cause deep vein thrombosis (DVT).
  • Acute compartment syndrome: Bleeding due to hamstring injury would increase THE pressure in the thigh region thereby compressing the major nerves and blood vessels that pass through the back of the thigh. This is an emergency condition.
  • Repeated injuries: It is mainly seen in those individuals who have persistent muscle weakness after recovering from a previous hamstrings injury or surgery. It is also common in athletes who return early to sports without complete recovery.
  • Myositis ossificans: The recovery from a severe hamstring injury may involve the formation of bony tissues in the affected region, this condition is called as myositis ossificans. It is one of the most common complications, in case of hamstring injury.

What is the Diagnosis of Hamstring Injury?

Early diagnosis of hamstring muscle injuries is essential to avoid further damages to the leg (or knee). Diagnosis includes:

Clinical Evaluation:

Physical examination provides observation for swelling behind the thigh and checking if the area is tender. It also includes an evaluation for the muscle strength of hamstrings.

Along with this, a complete medical history is done to understand the type of injury and the severity of the injury.


In this test, ultrasonic waves are passed through the affected thigh to observe for any abnormal findings such as a swelling of the internal tissues (edema).

Magnetic Resonance Imaging (MRI) Scans:

During this scan, a series of magnetic fields and radio waves are passed through the patient’s body to obtain a detailed image of the leg. It helps in viewing the deeper muscle injuries more accurately.

What is the Treatment for Hamstring injury?

Treatment of hamstring injuries does not require surgery in most of the cases. The treatment aims to make the patient return to his or her daily activities, as early as possible, and to prevent repeated recurrence of muscle strain.

Non-surgical Management:

The RICE (rest, ice, compression and elevation) protocol is recommended for most of the muscle injuries. It includes:

  • Rest: Patient has to take rest by refraining from doing any physical activities that cause pressure on the hamstring muscle. Doctors may also recommend crutches for walking to avoid exerting weight on the affected leg.
  • Ice: Applying ice or cold therapy helps in, reducing pain and swelling associated with the hamstring injury. Ice packs are to be applied for every 2-3 hours, for at least 15 minutes, from the time of injury until the pain subsides.
  • Compression: Applying a compression or elastic bandage around the affected thigh, to reduce swelling and to restrict the further movement of the leg.
  • Elevation: The affected leg has to be raised above the heart level, to reduce swelling and to drain the accumulated fluid towards the centre of the body.

Medical management:

Medications such as ibuprofen or acetaminophen are helpful in treating pain associated with muscle injury.

Physical therapy management:

Physiotherapy sessions start once the pain and swelling subsides. It includes:

  • Stretching exercises: These exercises are recommended initially to improve the flexibility of the muscle.
  • Strengthening exercises: Once the patient gains (full range of) movements in the affected leg, strengthening exercises are prescribed to build the muscle strength.

Surgical Management:

Surgery is recommended only in patients with a severe or grade-3 muscle injury and in cases, where there is a detachment of the bony fragment along with a muscle tear.

Doctors treat the complete tear in the muscle by stitching the muscle fibers together to restore the muscle structure.

In patients with detached bone (avulsion injury), hamstring muscle is pulled back to its original place, and the tendon is reattached to the bone.

In the acute stage of recovery from surgery, patients have to rest their leg to avoid immediate load on the repaired tendon. Use of crutches is recommended to prevent weight bearing on the operated leg for 3-4 weeks post-surgery.

Post-surgical physiotherapy is also recommended to improve the muscle strength and range of motion of the hip and knee joint.

How can Hamstrings Injury be Prevented?

Prevention of hamstrings injury is possible by taking the following measures:

  • Engaging of athletes in a regular warm-up program with or without a schedule of the sporting event.
  • Avoiding strenuous physical activities with tight leg muscles.
  • Practicing yoga, to improve the overall flexibility of the muscles.
  • Avoiding oneself from a sport or play until complete recovery from a muscle tear.
  • Practicing regular stretching and strengthening exercises to reduce muscle injuries.

Hamstring injuries are prevalent, but quick diagnosis and appropriate treatment help in the early prognosis of the patients.

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