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Medial patellar retinaculum

The medial patellar retinaculum is a strong fibrous band that contributes to the stabilization of the patella. It is formed by expansions of the vastus medialis obliquus (VMO), fibers of the quadriceps tendon, and the medial patellofemoral ligament (MPFL). It reinforces the joint capsule of the knee medially and plays a crucial role in maintaining patellar alignment and preventing lateral dislocation.

It is of great importance in knee biomechanics, orthopedic surgery, and sports medicine, particularly in conditions of patellar instability, maltracking, and trauma.

Synonyms

  • Medial retinaculum of the patella

  • Medial patellar stabilizing retinaculum

  • Medial reinforcement of knee capsule

Attachments

  • Origin: Medial border of the patella, medial epicondyle of the femur (via MPFL), and expansions of the vastus medialis obliquus

  • Course: Fibers fan out medially and inferiorly, blending with the joint capsule

  • Insertion: Tibial periosteum near the medial tibial condyle, blending with the fascia of the medial knee

Relations

  • Anteriorly: Subcutaneous tissue and skin of the medial knee

  • Posteriorly: Joint capsule and synovium of the knee

  • Superiorly: Quadriceps tendon and vastus medialis obliquus muscle

  • Inferiorly: Medial collateral ligament (MCL) and tibial periosteum

  • Laterally: Blends with medial edge of the patella and patellar tendon

Nerve Supply

  • Supplied by branches of the femoral nerve through the vastus medialis muscle

Arterial Supply

  • Genicular branches of the femoral and popliteal arteries, primarily the superior medial genicular artery

Venous Drainage

  • Corresponding genicular veins drain into the popliteal vein

Function

  • Reinforces the medial aspect of the knee joint capsule

  • Provides static and dynamic stability to the patella

  • Resists lateral displacement of the patella during knee motion

  • Works with MPFL and VMO to maintain correct patellar tracking

Clinical Significance

  • Injury or laxity contributes to patellar instability and recurrent dislocations

  • Commonly injured during acute lateral patellar dislocation

  • Repair or reconstruction may be required in recurrent instability

  • Target structure in imaging when evaluating knee trauma or maltracking syndromes

MRI Appearance

T1-weighted images:

  • Retinaculum appears as a thin, low-signal band along the medial patella

  • Surrounded by fat, which is bright and improves visibility

T2-weighted images:

  • Normal retinaculum appears low signal

  • Injury, sprain, or tear appears as bright hyperintense areas within the band

STIR (Short Tau Inversion Recovery):

  • Normal retinaculum remains dark

  • Pathology (strain, inflammation, edema, tear) shows bright hyperintensity

Proton Density Fat-Saturated (PD FS):

  • Normal retinaculum: low signal band

  • Partial or complete tears appear as bright hyperintense gaps

T1 Fat-Sat Post-Contrast:

  • Normal retinaculum shows minimal or no enhancement

  • Injured or inflamed retinaculum shows focal enhancement

  • Adjacent synovitis or capsular pathology may enhance

CT Appearance

Non-Contrast CT:

  • Retinaculum not distinctly visible, but patellar malalignment and avulsion fractures at its attachments may be detected

  • Appears as a thin soft tissue density band along medial patella if thickened

Post-Contrast CT:

  • Retinaculum itself enhances poorly

  • Enhancement may be seen in associated soft tissue edema, synovitis, or hematoma

MRI images

Medial patellar retinaculum axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Medial patellar retinaculum coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Medial patellar retinaculum sag cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Medial patellar retinaculum anatomy image mri 3t

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Medial patellar retinaculum anatomy image

CT image

Medial patellar retinaculum ct axial image

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Medial patellar retinaculum ct sag image