Gracilis Tendon (Distal): Anatomy, Insertion, Function, Clinical Significance, MRI & CT Imaging

Topic

Gracilis tendon (Distal)

The gracilis tendon is the distal continuation of the gracilis muscle, a long, slender muscle of the medial thigh. The tendon descends along the medial side of the knee and inserts on the anteromedial surface of the tibia. Together with the tendons of the sartorius and semitendinosus, it forms the pes anserinus. The distal gracilis tendon is clinically significant because it is frequently harvested for tendon grafts in ACL and other ligament reconstructions, and it is a common site of overuse injuries and bursitis.

Synonyms

Distal tendon of gracilis
Gracilis insertion tendon
Pes anserinus tendon (part)

Origin and Insertion

Origin: From the gracilis muscle belly in the medial thigh
Course: The tendon runs distally along the medial aspect of the thigh, narrows as it passes the medial knee, and joins the tendons of sartorius and semitendinosus
Insertion: Inserts onto the anteromedial surface of the tibia just below the tibial tuberosity, forming part of the pes anserinus complex

Nerve Supply

Supplied by the obturator nerve (anterior branch, L2–L3)

Arterial Supply

Medial circumflex femoral artery
Obturator artery branches
Genicular branches of the popliteal artery (distal tendon region)

Venous Drainage

Parallels the arterial supply, draining into profunda femoris and femoral vein

Function

Contributes to knee flexion
Aids in internal rotation of the tibia on the femur when the knee is flexed
Provides dynamic medial stability to the knee joint
Important role in reconstructive surgery (commonly used tendon graft source)

Clinical Significance

Pes anserinus bursitis: Common cause of medial knee pain, often in athletes and older adults
Tendon graft harvest: Used in ACL, MCL, and PCL reconstruction
Overuse injuries: Can present with tendonitis or partial tears
Imaging relevance: Key structure in evaluation of medial knee pathology on MRI and CT

MRI Appearance

T1-weighted images:

Tendon appears as a linear, very low signal intensity structure
Surrounded by bright fat, which enhances tendon delineation

T2-weighted images:

Normal tendon: dark/low signal intensity
Tendinopathy or tear: focal bright signal intensity within or around tendon

STIR (Short Tau Inversion Recovery):

Normal tendon: dark low signal
Edema, inflammation, or bursitis: bright hyperintense signal adjacent to tendon

Proton Density Fat-Saturated (PD FS):

Normal tendon: dark low signal
Tendinopathy, tear, or bursitis: bright hyperintense signal

T1 Fat-Sat Post-Contrast:

Normal tendon: minimal or no enhancement
Pathology: enhancement of surrounding soft tissues in bursitis or inflammation; tendon tears may enhance along disrupted margins

CT Appearance

Non-Contrast CT:

Tendon itself poorly visualized, appears as linear soft tissue density
Calcifications or enthesopathy may appear as hyperdense foci near tibial insertion

Post-Contrast CT: