Biceps femoris tendonitis (also called biceps femoris tendinitis) is an overuse injury that affects the lower portion of the biceps femoris tendon, located near the outside of the back of the knee. The biceps femoris is one of the three hamstring muscles. The muscle inserts on the fibular head just below the outer aspect of the knee. Tendonitis caused by inflammation or irritation at this site can lead to knee pain and dysfunction, particularly in active individuals. So, what is biceps femoris tendonitis, and how do we treat it? 

Causes of Biceps Femoris Tendonitis

Biceps femoris tendonitis is typically caused by repetitive strain or overload at the tendon insertion onto the fibular head. Several contributing factors can predispose an athlete to this condition:

  • Training errors such as sudden increases in running intensity, hill work, or sprinting

  • Weak gluteal and core muscles, placing excessive load on the hamstrings

  • Tightness in the hamstring or iliotibial band, increasing traction on the biceps femoris tendon

  • Poor lumbopelvic control, which can increase posterior chain strain during activity

Over time, these repetitive stresses result in swelling and inflammation of the tendon, leading to pain and altered function. 

Biceps femoris Tendonitis Symptoms 

Patients typically report pain at the back and outer part of the knee, often just below the joint line. The pain usually develops gradually and may worsen with activity, especially sprinting, squatting, cycling, or pushing off from a bent knee. Some describe aching pain after exercise. Occasionally, the pain may radiate into the lateral hamstring or calf region, though the tenderness remains localised to the distal tendon.

In more advanced cases, swelling or thickening near the tendon insertion may be palpable. 

Medical Assessment

A thorough history and physical examination are key to diagnosing biceps femoris tendinitis. On examination, the following findings are typical:

  • Tenderness at the fibular head or along the distal biceps femoris tendon

  • Pain with resisted hamstring activities

  • Discomfort on stretching the hamstrings

  • Negative joint tests  help rule out intra-articular knee pathology

  • Functional testing (e.g., single leg bridge, Nordic curl) may reveal weakness or pain in the posterior chain

It is essential to differentiate outer knee pain from other causes, such as iliotibial band syndrome, lateral meniscal injury, or LCL strain. If the diagnosis is uncertain, imaging may be required.

Imaging

Ultrasound is a valuable imaging tool for evaluating the biceps femoris tendon. It can show tendon thickening or neovascularity, particularly near the fibular head. 

MRI offers a more detailed view of the hamstring tendons and helps identify other pathologies, such as lateral meniscus degeneration or bursitis. 

Treatment of Biceps Femoris Tendonitis

Rehabilitation

The foundation of treatment for biceps femoris tendonitis is a structured rehabilitation program involving the following key aspects: 

  • Activity modification to reduce tendon load

  • Isometric hamstring exercises to reduce pain while maintaining strength

  • Progression to isotonic loading, such as hamstring bridges, step-ups, lunges, hamstring curls and Nordic curls.

  • As strength improves, we introduce our-level hamstring plyometric

  • Careful reintroduction to sport-specific drills, gradually building sprinting and deceleration work

Adjuncts to rehabilitation 

Extracorporeal shockwave therapy (ESWT) is a noninvasive treatment that can stimulate healing in chronic tendon conditions by promoting tendon regeneration. Several studies have shown benefit in lower limb tendinopathies, and we may consider it for biceps femoris tendinitis that has not responded to basic rehab.

Topical glyceryl trinitrate (GTN) patches have been explored in treating chronic tendinopathy. Applied near the painful tendon, GTN patches may improve tendon healing by increasing local nitric oxide levels, which enhance collagen synthesis. However, we must monitor side effects like skin irritation and headaches. 

Collagen Supplements for Tendonitis

Recent evidence suggests that hydrolysed collagen taken 30 minutes before may improve pain associated with tendonitis. 

Injection Therapy

In cases resistant to conservative treatment, we consider ultrasound-guided injections. Options include:

  • Corticosteroid injection, typically around the tendon insertion, for short-term pain relief. This is used cautiously due to the risk of tendon weakening and rupture.

  • Platelet-rich plasma (PRP) injections stimulate tendon healing by delivering growth factors. We obtain PRP by spinning down whole blood and separating the plasma from the red and white cells. Evidence for PRP in hamstring tendinopathy is evolving. Still, it may offer benefits in selected chronic cases.

Surgical intervention is rarely needed and is reserved for cases with structural tendon tears or fibrotic adhesions that fail non-operative care.

Final Word from Sportdoctorlondon regarding Biceps Femoris Tendonitis 

Biceps femoris tendonitis is a relatively under-recognised cause of outer knee pain, particularly in athletes who rely on robust hamstring activation. Early diagnosis and a structured, progressive rehab program are essential to recovery. In more persistent cases, we consider adjunctive treatments such as shockwave therapy, GTN patches, and injections. With the right approach, most individuals can return to full activity without surgery. 

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