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Trochlear groove

The trochlear groove, also called the femoral trochlea or patellar groove, is a bony depression located on the anterior distal femur. It forms the articular surface for the patella and is a critical component of the patellofemoral joint. The groove is concave centrally with medial and lateral femoral condyles forming raised margins, the lateral ridge being typically more prominent to stabilize the patella during knee motion.

The depth, alignment, and morphology of the trochlear groove are clinically significant in conditions such as patellofemoral pain syndrome, patellar instability, and trochlear dysplasia.

Synonyms

  • Femoral trochlea

  • Patellar groove

  • Intercondylar sulcus (anterior femur)

Location and Boundaries

  • Situated on the anterior aspect of the distal femur

  • Extends superiorly from the supracondylar region down to the anterior junction with the femoral condyles

  • Medially: Medial femoral condyle

  • Laterally: Lateral femoral condyle

  • Posteriorly: Continuous with the intercondylar fossa and femoral condyles

Relations

  • Anteriorly: Patella and overlying quadriceps tendon/patellar tendon

  • Posteriorly: Femoral condyles and intercondylar notch

  • Medially: Medial patellar retinaculum, medial femoral condyle

  • Laterally: Lateral patellar retinaculum, lateral femoral condyle

  • Superiorly: Quadriceps tendon blending into patella

  • Inferiorly: Patellar tendon attaching to tibial tuberosity

Function

  • Provides a stable articular track for the patella during knee flexion and extension

  • Distributes forces between the patella and femur

  • Lateral ridge resists patellar dislocation

  • Plays a role in smooth knee biomechanics, reducing friction at the patellofemoral joint

Clinical Significance

  • Trochlear dysplasia: Abnormally shallow groove, predisposing to patellar instability or dislocation

  • Chondral/osteochondral lesions: Can occur from trauma or degenerative change

  • Patellofemoral pain syndrome: Often associated with trochlear morphology abnormalities

  • Imaging: Evaluation essential in knee MRI/CT for patellar tracking and instability assessment

MRI Appearance

T1-weighted images:

  • Bone cortex shows low signal intensity

  • Bone marrow in the trochlear groove appears intermediate to bright depending on fatty content

  • Cartilage lining appears as intermediate signal

T2-weighted images:

  • Cartilage appears bright relative to bone

  • Bone cortex remains dark

  • Bone marrow shows intermediate to bright signal

  • Fluid in patellofemoral joint appears bright within the groove

STIR (Short Tau Inversion Recovery):

  • Bone marrow edema within the groove shows bright hyperintensity

  • Normal marrow: suppressed to intermediate signal

  • Cartilage remains relatively bright

Proton Density Fat-Saturated (PD FS):

  • Cartilage of the trochlear groove shows high signal

  • Fluid collections or chondral injuries appear as bright foci

  • Bone marrow edema stands out as hyperintense after fat suppression

T1 Fat-Sat Post-Contrast:

  • Normal cartilage and marrow: mild uniform enhancement

  • Synovial inflammation, chondral lesions, or tumors: focal or diffuse enhancement

  • Osteochondritis dissecans or subchondral cysts: rim enhancement with non-enhancing core

CT Appearance

Non-Contrast CT:

  • Trochlear groove appears as a bony depression on anterior distal femur

  • Normal cortical margins are smooth and dense

  • Dysplastic groove appears shallow or flattened

  • Osteochondral lesions may be visualized as cortical defects or sclerosis

Post-Contrast CT:

  • Bone cortex does not enhance

  • Enhancement may highlight adjacent synovial thickening, effusion, or tumors

  • Chondral defects better evaluated with CT arthrography (contrast outlines cartilage surface)

MRI image

Trochlear groove axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

CT image

Trochlear groove ct axial image