Proximal Hamstring Injury

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Proximal Hamstring Injury

Proximal hamstring injury occurs frequently in individuals participating in running, jumping, and kicking sports. The peak incidence is reported to be in the 16 to 25-year age group.

The hamstring muscles are located in the posterior thigh and are comprised of the semimembranous medially, long, and short heads of the biceps femoris laterally and the semitendinosus in between. The long head of the biceps femoris, semimembranosus, and semitendinosus muscles are innervated by the tibial portion of the sciatic nerve, while the short head of the biceps femoris muscle is innervated by the peroneal portion of the sciatic nerve.

The semimembranosus, semitendinosus, and the long head of the biceps femoris muscles all originate from the ischial tuberosity and insert below the knee, contributing to hip extension and knee flexion.

Proximal hamstring injuries, including tendon avulsion, are more common than distal injuries regardless of the muscle involved. Sports requiring high-speed running and maximum stretch of the hamstrings are associated with an increased risk of first-time hamstring injury. In high-speed running, the hamstrings are required to contract eccentrically to decelerate the leg during the end of the swing phase of running (when the leg is fully forward). Injury results from overloading the muscle when a sudden forceful eccentric contraction occurs. Injuries resulting from the maximum stretch of the hamstrings occur when the muscle is stretched beyond its elastic capacity with the hip and knee joints at their extreme limits of motion (e.g., a high leg raise performed by a dancer, or in hurdling).

Most hamstring injuries occur in the musculotendinous junction and are graded according to their severity (as described below). Tendon avulsion injuries (where a piece of the ischial tuberosity is separated) are more common in young (skeletally immature) individuals and are rare in adults. A previous hamstring injury is the most recognized risk factor for recurrent hamstring injuries. 

Types of Hamstring Injury

Type 1 hamstring injuries usually occur during high-speed running or sprinting and typically affect the long head of the biceps femoris muscle. The pain is usually felt further down from the ischial tuberosity and can cause a significant decline in function initially. However, this type of injury typically has a quicker rehabilitation time when compared to Type 2 hamstring injuries.

Type 2 hamstring injuries usually occur due to excessive lengthening of the muscle and usually affect the proximal free tendon of the semimembranosus muscle. The pain is usually felt closer to the ischial tuberosity and can extend up into the buttock. Rehabilitation for Type 2 injuries may take slightly longer than for Type 1 injuries.

Grading of Hamstring Injury

The severity of hamstring injury is classified according to the severity of pain, weakness, and loss of function:

• Grade I – Mild pain or swelling, non-appreciable tissue disruption, with no or minimal loss of strength
• Grade II – Moderate pain and swelling, partial or incomplete tear of the hamstring, with moderate loss of strength
• Grade III – Severe pain and swelling, complete tear of the hamstring, with significant loss of function

Risk Factors for Hamstring Injury

• Previous hamstring injury
• High-speed running
• Inadequate warm-up
• Increased training volume
• Muscle fatigue
• Hamstring inflexibility
• Hamstring weakness (particularly in comparison to quadriceps strength)
• Lower Crossed Syndrome (also known as Pelvic Crossed Syndrome)
• Biomechanical dysfunction of the kinetic chain

Differential Diagnosis for Proximal Posterior Thigh Pain

• Proximal hamstring injury
• Myofascial pain syndrome
• Hamstring syndrome
• Lumbosacral facet syndrome
• Lumbosacral radiculopathy
• Piriformis syndrome
• Sacroiliac joint injury
• Lumbosacral discogenic pain syndrome
• Sciatic nerve compression by inferior or superior gluteal artery aneurysm
• Pelvic bone tumor

• Localised pain in the upper posterior thigh or lower buttock
• Pain onset is often sudden, occurring during high-risk activities (e.g., high-speed running or kicking)
• Pain is aggravated by activities such as running, jumping and climbing stairs
• Pain or discomfort when sitting
• The patient may report a popping sensation or sound at the time of the injury
• Tightness in the posterior thigh

• May present with an antalgic gait
• Swelling may be present in the area of the proximal hamstring tendons
• A visible or palpable muscle defect may be present
• Ecchymosis over the buttock and the posterior thigh may be present in more severe injuries
• Local tenderness in the upper posterior thigh
• Knee flexion and hip extension weakness are typically present
• A positive Modified Bent-Knee test
• A positive Puranen-Orava test
• Pain on resisted knee flexion

Musculoskeletal Ultrasonography and Magnetic Resonance Imaging (MRI) are considered the best imaging methods for assessing hamstring injuries.

Ultrasonography is most useful in the acute phase in detecting inflammatory fluid in the soft tissue, but its sensitivity declines if scanning is delayed. Ultrasonography is also useful for detecting avulsion injuries and damaged muscle tissues.

MRI is more reliable than Ultrasonography in detecting hamstring tendon injuries, injuries in the deeper musculotendinous junction, and osseous avulsions.

Plain radiographs may also be useful in helping to rule out bony fractures and osseous avulsions.

The following are examples of red flags for patients presenting with posterior upper thigh and buttock pain:

• History of a significant injury
• Severe pain
• Unrelenting pain
• Nocturnal pain
• Unexplained weight loss
• Fever
• Deformity
• Significant swelling
• Presence of tingling, numbness, burning, or other neurological impairment
• Loss of distal leg pulses
• Significant loss of range of motion
• Severe tenderness on palpation or severe pain with any examination procedure

If any red flags are identified during history taking and clinical examination, referral for urgent medical evaluation and further investigation is warranted.

Ice or Heat?

The application of ice, particularly in the acute phase of an injury, is a safe and effective means of reducing pain whilst also reducing secondary hypoxic injury to the surrounding uninjured tissue by lowering tissue metabolism. This means that the damage is potentially confined to the injured area.

Some practitioners advocate using moist heat in the subacute or chronic phase of an injury. However, we have found that patients often benefit from the continued application of ice to reduce discomfort and manage inflammation. The application of ice helps to decrease the patient’s pain which then allows them to tolerate some movement. This helps the patient to maintain range of motion, stimulates circulatory perfusion, and prevents potential atrophy, all of which help to speed up recovery.

Heat therapy may not be the best option for some musculoskeletal injuries as they often involve inflammation of the damaged tissues. Applying heat can potentially increase blood flow to the area and worsen the inflammation, leading to more pain and discomfort. Whilst heat therapy may provide temporary pain relief, by relaxing muscles and increasing blood flow, it does not address the underlying cause of the impingement. Therefore the use of heat therapy may delay recovery.

Lower Crossed Syndrome

Lower Crossed Syndrome (LCS) is considered a risk factor for the development of proximal hamstring injuries. LCS is a postural imbalance characterized by tightness and/or overactivity of the hip flexors and lower back muscles, and weakness and/or underactivity of the gluteal and abdominal muscles. The term ‘crossed’ refers to the diagonal relationship between the overactive and underactive muscle groups.

Treatment for LCS typically involves stretching the tight and/or overactive muscles and strengthening the weak and/or underactive muscles, as well as performing other postural correction exercises such as core strength exercises.

Proximal Posterior Thigh Pain Caused by Myofascial Pain Syndrome

In patients presenting with proximal posterior thigh pain, a complete clinical examination should include checking for any myofascial pain syndrome as a concomitant or the primary cause of the patient’s pain. In patients presenting with upper posterior thigh pain, the main muscle to examine for myofascial trigger points is the hamstring muscle.

• The trigger points associated with myofascial pain syndrome may be located anywhere within a muscle and its fascia. Therefore, the entire muscle should be examined thoroughly. However, based on our clinical experience, the common locations for trigger points are presented below.