Snapping biceps femoris tendon

Snapping biceps femoris tendon or snapping biceps femoris syndrome is an infrequent pathology where the distal biceps tendon dislocates over the fibular head and relocates painfully.

Epidemiology

Snapping biceps femoris tendon is considered an uncommon entity ^1-4.

Associations

It has been associated with morphological variations of the distal biceps femoris tendon insertion and the fibular head ^1,2.

Diagnosis

Major clues to the diagnosis include a typical clinical history and typical findings on clinical examination.

There are no definite diagnostic criteria due to the infrequency of this condition.

Clinical presentation

Presenting symptoms include chronic lateral knee pain associated with a visible and/o audible clicking or snapping especially on activities with deep knee flexion as e.g. squats or sitting in a low seat ^2-4.

Physical examination typically reveals a visible subluxation of the biceps femoris tendon over the lateral aspect of the knee ^2-4. Preventing the tendon from subluxation by manual pressure on the point of the fibular head, where it crosses can aid in the verification of the diagnosis ³.

Pathology

Snapping biceps femoris tendon is a result of distal biceps femoris tendon subluxation over the fibular head on deep knee flexion and relocation on knee extension ³.

Radiographic features

Ultrasound

The snapping distal biceps femoris tendon might be reproduced on dynamic ultrasound examination while flexing the knee. 

MRI

MRI might show thickening or tear of the distal biceps femoris tendons or it might not show any abnormality ^3,4. It will also aid in excluding any injury to other posterolateral corner structures of the knee and/or meniscal tears ³.

Radiological report

The radiological report should include a description of the definable distal biceps tendon morphology including:

• distal biceps femoris tendon injury
• lateral collateral ligament injury
• injury of other posterolateral corner structures
• meniscal tears

Treatment and prognosis

Due to its rarity, there is little evidence concerning the treatment. Surgery is an acceptable option if conservative measures fail and include a variety of techniques including direct reattachment of the affected arms with suture anchors ³ rerouting the tendon through a bone tunnel or partial resection of the tendon ^2,4.

History and etymology

The first report of a snapping distal femoris tendon in the literature might have been made by G Kristensen and colleagues in 1989 ^5,6.