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Patellar articular cartilage

The patellar articular cartilage is the specialized hyaline cartilage covering the posterior surface of the patella. It is the thickest articular cartilage in the human body, ranging from 4–6 mm, adapted to withstand the high compressive and shear forces of the patellofemoral joint. The cartilage ensures smooth articulation between the patella and the femoral trochlea, distributing load and reducing friction during knee motion.

This cartilage is frequently involved in degenerative disease, trauma, and overuse syndromes, making it a critical structure in musculoskeletal imaging and sports medicine.

Synonyms

  • Patellar chondral cartilage

  • Posterior patellar cartilage

  • Patellofemoral joint cartilage

Structure

  • Composed of hyaline cartilage with a highly organized extracellular matrix of type II collagen and proteoglycans

  • Thickness varies across regions: thickest at the medial and lateral facets, thinner at the periphery

  • Contains chondrocytes embedded within lacunae, surrounded by zonal collagen architecture

  • Avascular, aneural, and alymphatic — nutrition is provided by diffusion from synovial fluid

Origin and Insertion

  • Not applicable as cartilage has no true muscular or tendinous origin/insertion

  • Instead, it is firmly attached to the subchondral bone of the patella

Relations

  • Anteriorly: Subchondral bone of the patella and patellar trabeculae

  • Posteriorly: Femoral trochlear cartilage forming the patellofemoral articulation

  • Superiorly: Quadriceps tendon inserting into the patella

  • Inferiorly: Continuity with patellar tendon attaching patella to tibial tuberosity

  • Laterally/Medially: Medial and lateral retinacula stabilizing the patella

Nerve Supply

  • Articular cartilage is aneural (no direct nerve supply)

Arterial Supply

  • Receives nutrition via diffusion from synovial fluid and subchondral bone capillaries

Venous Drainage

  • Not directly present in cartilage; venous return occurs via adjacent subchondral bone venous channels

Function

  • Provides a smooth, low-friction surface for patellofemoral articulation

  • Distributes compressive forces from quadriceps to femoral trochlea

  • Protects underlying patellar bone from high stress loads

  • Facilitates efficient movement in knee extension and flexion

Clinical Significance

  • Chondromalacia patellae: Softening and degeneration of patellar cartilage

  • Osteoarthritis: Common site for patellofemoral compartment degeneration

  • Patellar dislocation/subluxation: May damage patellar cartilage

  • Cartilage defects: Important targets for MRI in sports-related injury

  • Surgical relevance: Procedures like microfracture, autologous chondrocyte implantation, and osteochondral grafting often involve this cartilage

MRI Appearance

T1-weighted images:

  • Cartilage appears as a smooth low-to-intermediate signal band covering the patella

  • Subchondral fat and marrow provide contrast as brighter signal

T2-weighted images:

  • Normal cartilage shows intermediate signal intensity with smooth homogeneous appearance

  • Focal defects, fibrillation, or chondromalacia appear as areas of high signal intensity

STIR (Short Tau Inversion Recovery):

  • Cartilage remains low-to-intermediate signal

  • Subchondral edema or chondral injury appears bright hyperintense

Proton Density Fat-Saturated (PD FS):

  • Cartilage appears as intermediate signal intensity with sharp margins

  • Chondral lesions and fissures appear as bright hyperintense foci or lines

T1 Fat-Sat Post-Contrast:

  • Normal cartilage shows minimal enhancement

  • Chondral pathology may enhance if there is adjacent synovitis, granulation tissue, or vascularized repair response

CT Appearance

Non-Contrast CT:

  • Cartilage itself is not well visualized (non-calcified tissue is radiolucent)

  • Appears as a thin radiolucent space between patella and femoral trochlea

  • Calcification within cartilage (chondrocalcinosis) may be seen as dense foci

Post-Contrast CT (Arthro-CT):

  • With intra-articular contrast, cartilage defects appear as contrast filling within fissures or defects

  • CT arthrography can outline cartilage thickness and surface irregularities

  • Osteochondral lesions appear as defects in cartilage with subchondral bone changes

MRI image

Patellar articular cartilage (chondral cartilage) sag cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000_00001

MRI image

Patellar articular cartilage (chondral cartilage) axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000