Distal Biceps Femoris Tendon: Anatomy, Insertion, Relations, Function, Clinical Significance, MRI & CT Imaging

Topic

Distal biceps femoris tendon

The distal biceps femoris tendon is the terminal structure of the biceps femoris muscle, one of the hamstring muscles. It plays a crucial role in knee stability, particularly as part of the posterolateral corner (PLC) of the knee joint. The tendon has complex attachments and is frequently involved in sports injuries, trauma, and posterolateral knee instability.

Synonyms

Distal hamstring tendon (biceps femoris)
Lateral hamstring tendon
Posterolateral corner stabilizer (component)

Origin and Insertion

Origin (muscle belly): Long head of biceps femoris arises from the ischial tuberosity; short head arises from the linea aspera and lateral supracondylar ridge of femur
Course: Fibers converge laterally in the thigh and descend toward the knee, forming a strong distal tendon
Insertion:
- Main tendon inserts on the fibular head (anterolateral aspect)
- Additional expansions attach to the lateral collateral ligament (LCL), iliotibial band (ITB), lateral tibial condyle, and posterolateral capsule

Relations

Anteriorly: Lateral collateral ligament and capsule of knee joint
Posteriorly: Popliteal fossa contents (popliteal vessels, tibial nerve)
Medially: Lateral tibial condyle and popliteus tendon
Laterally: Iliotibial band

Nerve Supply

Tibial division of sciatic nerve (long head)
Common fibular division of sciatic nerve (short head)

Arterial Supply

Branches from profunda femoris artery
Genicular branches of popliteal artery

Venous Drainage

Popliteal vein via corresponding venous tributaries
Profunda femoris vein

Function

Flexion of the knee
External rotation of the tibia when the knee is flexed
Contributes to posterolateral corner stability by reinforcing the fibular head and LCL region

Clinical Significance

Injuries: Frequently strained or torn in hamstring injuries, especially in sprinting athletes
PLC injuries: Critical stabilizer; damage can cause posterolateral rotatory instability
Avulsion injuries: Tendon avulsion at fibular head may mimic lateral collateral ligament rupture
Surgical relevance: Landmark in PLC reconstruction and knee ligament surgeries
Imaging importance: Must be carefully evaluated in multi-ligament knee injuries

MRI Appearance

T1-weighted images:

Tendon appears as a low-signal linear structure inserting on the fibular head
Surrounded by high-signal fat planes, aiding identification

T2-weighted images:

Normal tendon remains dark/low signal
Tendinopathy, strain, or partial tear shows linear or focal bright signal within tendon fibers
Complete tear shows tendon discontinuity with surrounding bright edema

STIR (Short Tau Inversion Recovery):

Normal tendon remains dark
Pathology (strain, tear, inflammation) shows bright hyperintensity around or within tendon substance

Proton Density Fat-Saturated (PD FS):

Normal tendon: dark low-signal band
Pathology: bright hyperintensity at site of tendinosis or tear, with surrounding edema well depicted

T1 Fat-Sat Post-Contrast:

Normal tendon shows minimal or no enhancement
Pathology shows contrast enhancement in cases of tendinopathy, enthesitis, or peritendinous inflammation

CT Appearance

Non-Contrast CT:

Tendon not distinctly seen, appears as a soft tissue band inserting on fibular head
Avulsion fractures may be detected at insertion site on fibular head
Chronic calcific tendinopathy may show focal calcification

Post-Contrast CT:

Normal tendon shows no significant enhancement
Inflammatory or neoplastic processes show enhancement of tendon sheath or adjacent soft tissues
Avulsion injuries or hematomas may show surrounding soft tissue changes

MRI images