Patellofemoral Joint in the Sagittal Plane: Articular Surface Geometry and Osseous Anatomy

The authors studied articular surface geometry and osseous anatomy of the patella and of the femoral trochlea in the sagittal plane. They analyzed the patellofemoral joint in the midline sagittal plane on cryosections from a cadaver knee. On magnetic resonance arthrograms, the authors analyzed the patella of 38 patients and the femoral trochlea of 24 patients. The cryosections revealed significant differences in the bony anatomy and corresponding articular surface geometry of the patellofemoral joint in the sagittal plane: The patella exhibited a posteriorly oriented convex articular cartilage surface; the osseous contour of the patella revealed a anteriorly oriented concave "indentation" or "imprint." On magnetic resonance arthrotomograms, the retropatellar cartilage surface and corresponding osseous contour of the patella did not match in any of the investigated knees. The convex articular cartilage surface of the deepest parts of the intercondylar sulcus and the corresponding deepest osseous contour of the femoral trochlea did not match on sagittal midline magnetic resonance arthrotomograms. Because multiplanar magnetic resonance arthrotomography can distinguish between the joint surface geometry and subchondral osseous morphology of the patellofemoral joint, this imaging modality allows the surgeon and the radiologist to appraise the true articulating joint surfaces and underlying bony architecture of the knee in the sagittal plane. Thus, the authors recommend magnetic resonance arthrotomography in the sagittal plane as an imaging technique of choice in assessing sagittal morphology, congruence, and joint contact zones of the patellofemoral joint.