Topics

Topic

design image
Arcuate popliteal ligament

The arcuate popliteal ligament is a Y-shaped fibrous structure that reinforces the posterior aspect of the knee joint capsule. It arises from the fibular head and divides into a lateral band and a medial band, both contributing to the posterolateral stability of the knee. The ligament blends with other posterolateral corner structures and is closely associated with the popliteus muscle and tendon.

Its importance lies in stabilizing the knee against hyperextension and external rotation. Injury to this ligament is often associated with posterolateral corner injuries and can be detected on advanced imaging.

Synonyms

  • Arcuate ligament of the knee

  • Posterolateral arcuate ligament

  • Arcuate complex (with other posterolateral corner structures)

Origin and Insertion

  • Origin: Posterior aspect of the fibular head

  • Lateral band (lateral arcuate band):

    • Runs upward and laterally, attaching to the lateral femoral condyle

    • Blends with the lateral gastrocnemius tendon and posterior capsule

  • Medial band (medial arcuate band):

    • Runs upward and medially, blending with the oblique popliteal ligament and posterior capsule

    • Merges with fibers surrounding the popliteus tendon

Relations

  • Anteriorly: Popliteus muscle and tendon, posterior joint capsule

  • Posteriorly: Popliteal vessels, small saphenous vein, tibial nerve (in popliteal fossa)

  • Laterally: Lateral collateral ligament and lateral femoral condyle

  • Medially: Oblique popliteal ligament and posterior aspect of medial femoral condyle

  • Superiorly: Blends with capsule and femoral condyles

  • Inferiorly: Fibular head and associated structures (fibular collateral ligament, biceps femoris tendon)

Nerve Supply

  • Articular branches from the tibial nerve and common fibular nerve (via genicular branches)

Arterial Supply

  • Genicular branches of the popliteal artery

Venous Drainage

  • Genicular veins draining into the popliteal vein

Function

  • Reinforces the posterior knee joint capsule

  • Provides posterolateral stability of the knee

  • Resists hyperextension and external rotation forces

  • Works with the oblique popliteal ligament to stabilize the posterior knee

Clinical Significance

  • Injured in posterolateral corner injuries (often with fibular collateral ligament, popliteus tendon)

  • Tears can cause posterolateral rotatory instability of the knee

  • Seen in association with trauma, sports injuries, and knee dislocations

  • Important structure to assess on MRI for chronic instability and surgical planning

MRI Appearance

T1-weighted images:

  • Ligament appears as a thin, low-signal band

  • Surrounded by intermediate signal capsule and bright posterior fat planes

T2-weighted images:

  • Normal ligament remains low signal

  • Partial or complete tears show disruption and high-signal intensity within fibers

  • Surrounding edema may also be seen as bright signal

STIR (Short Tau Inversion Recovery):

  • Ligament remains dark in normal state

  • Tears, sprains, or edema show bright hyperintensity in and around the ligament

Proton Density Fat-Saturated (PD FS):

  • Normal ligament is dark (low signal)

  • Pathologic changes appear bright, showing fiber discontinuity or surrounding edema

T1 Fat-Sat Post-Contrast:

  • Normal ligament shows minimal enhancement

  • Pathologic conditions (sprain, synovitis, post-traumatic changes) may show focal or diffuse enhancement of surrounding soft tissues

CT Appearance

Non-Contrast CT:

  • Ligament is not well visualized directly; appears as a thin soft tissue density band posterior to the knee joint

  • Surrounding fat helps outline its course

  • Avulsion fractures at fibular head (arcuate sign) may be detected

Post-Contrast CT:

  • Ligament itself does not enhance

  • Surrounding soft tissue inflammation, hemorrhage, or synovitis may enhance

  • Useful in evaluating associated fractures and avulsion injuries

MRI images

Arcuate popliteal ligament axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Arcuate popliteal ligament axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000_00001

MRI images

Arcuate popliteal ligament coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Arcuate popliteal ligament sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Arcuate popliteal ligament ct sagittal image