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Other Terms: Knee cap, Knee bone
This bone is of the sesamoid variety, meaning a bone that forms within a tendon. It is the largest of the sesamoid bones. The patella is positioned in the posterior half of the quadriceps tendon just anterior to the knee joint. It is a flattened bone with a curved superior margin and a triangular inferior border. An indistinct vertical ridge separates the posterior articular surface into medial and lateral articular surfaces, the lateral articular facet being larger than the medial articular facet. The anterior face of the bone is rough for attachment of the quadriceps tendon. The bone consists of a thin plate of compact bone covering a dense trabecular network of spongy bone.
From the Latin, patella is the diminutive form of patina denoting a small, broad shallow dish or pan. Today the Italian word for frying pan is padella.
The posterior surface of the patella articulates with the anterior surface of both lateral and medial condyles of the femur.
The patella ossifies from multiple centers that arise during the third year, but sometimes these centers do not appear until as late as the sixth year. These centers rapidly fuse and ossification is typically complete by puberty.