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Medial articular facet of patella

The medial articular facet of the patella is one of the two major articular surfaces on the posterior aspect of the patella. It articulates with the medial femoral condyle and plays a crucial role in patellofemoral joint mechanics. It is typically smaller and steeper than the lateral facet. The morphology of the medial facet contributes significantly to patellar tracking, stability, and the distribution of forces across the patellofemoral joint. Variations or damage to this surface are associated with conditions such as chondromalacia patellae, patellar maltracking, and osteoarthritis.

Synonyms

  • Medial facet of the patella

  • Patellar medial articular surface

  • Medial patellofemoral surface

Muscular Attachments

  • The vastus medialis obliquus (VMO) inserts into the superomedial aspect of the patella, indirectly influencing the medial articular facet through stabilization.

  • Medial retinacular fibers also reinforce the medial border of the patella, maintaining medial alignment during knee extension.

  • The articular surface itself does not receive direct muscular insertion but is functionally related to medial stabilizers of the patella.

Relations

  • Anteriorly: Subcutaneous tissue and prepatellar bursa (overlying the patella)

  • Posteriorly: Medial femoral condyle (forms the patellofemoral articulation)

  • Medially: Medial patellar retinaculum, medial patellofemoral ligament (MPFL)

  • Laterally: Adjacent to the central ridge separating medial and lateral facets

  • Superiorly: Related to the quadriceps tendon insertion on patella

  • Inferiorly: Related to the patellar ligament extending to tibial tuberosity

Function

  • Forms part of the patellofemoral joint, articulating with the medial femoral condyle

  • Contributes to load distribution across the knee joint during flexion and extension

  • Provides stability in patellar tracking, aided by medial muscular and ligamentous attachments

  • Plays a role in force transfer from quadriceps to tibia via patella and patellar ligament

Clinical Significance

  • Site of chondral wear and chondromalacia, especially in patellar maltracking

  • Important landmark in patellar fractures and surgical planning

  • May be affected in patellofemoral osteoarthritis and instability syndromes

  • MRI is critical in assessing cartilage integrity, bone marrow changes, and subchondral pathology

MRI Appearance

T1-weighted images:

  • Subchondral bone marrow shows intermediate to bright signal intensity

  • Cartilage appears as intermediate signal

  • Fatty marrow (if present) contributes to higher signal intensity

T2-weighted images:

  • Subchondral bone marrow shows intermediate to bright signal intensity

  • Articular cartilage appears as intermediate to high signal depending on hydration and integrity

  • Focal edema or degeneration may increase signal

STIR (Short Tau Inversion Recovery):

  • Normal marrow signal is low

  • Pathologic changes (bone marrow edema, inflammation, fracture) appear bright hyperintense

Proton Density Fat-Saturated (PD FS):

  • Normal marrow signal is low

  • Abnormal changes (cartilage damage, edema, subchondral cysts) appear bright hyperintense

T1 Fat-Sat Post-Contrast:

  • Normal bone marrow shows minimal enhancement

  • Pathologic lesions (inflammatory, neoplastic, or osteochondral) show focal or diffuse enhancement

CT Appearance

Non-Contrast CT:

  • Medial facet visualized as a smooth cortical surface articulating with the medial femoral condyle

  • Subchondral bone appears dense and compact

  • Fractures, cortical irregularities, or osteophytes are well seen

Post-Contrast CT:

  • No significant enhancement of normal bone

  • Pathologic processes (infection, tumor, or inflammatory lesions) may show enhancement of adjacent soft tissues or marrow changes

  • CT arthrography may delineate cartilage defects over the facet

MRI image

Medial articular facet of patella coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

CT image

Medial articular facet of patella ct axial