Patello-femoral joint mechanics and pathology. 1. Functional anatomy of the patello-femoral joint

TLDR

Cadaver knee joints were mounted to simulate life‑like weight‑bearing forces, and patello‑femoral contact areas were mapped under load across the full range of motion using a dye method. During extension to 90° flexion the contact area sweeps from the inferior to the superior pole while the odd facet remains non‑contact; at ~135° flexion separate medial and lateral contact zones appear, the medial limited to the odd facet; beyond 90° a large tendon‑femoral contact area forms, and between 90°–135° the patella rotates, engaging the ridge between facets, which bears high load and correlates with cartilage lesions.

Abstract

Cadaver knee joints were mounted so that life-like forces of weight-bearing were simulated. The patello-femoral contact areas were defined under load throughout the range of movement by the dye method. During movement from extension to 90 degrees of flexion a band of contact sweeps across the patella from inferior to superior pole, but the odd facet makes no contact. At about 135 degrees of flexion separate medial and lateral contact areas form, the medial one limited to the odd facet. From extension to 90 degrees of flexion the patella holds the quadriceps tendon away from the femur, but in further degrees of flexion an extensive "tendo-femoral" contact area forms. Between 90 degrees and 135 degrees of flexion the patella rotates and the ridge between the medial and odd facets engages the femoral condyle. The odd facet is shown to be a habitual non-contact area and the ridge to be subject to high load, observations which correlate with cartilage lesions described in Part 2 of the paper.