Patella

Patella, or the kneecap is the largest sesamoid bone in our body. Other sesamoid bones could be found in the tendons of the hand and foot finger's flexor muscles at the regions of the higher bending and friction stress. The patella is incorporated in the tendon of the quadriceps femoris muscle and remarkably reduces its friction over the femur's patellar surface during active extension of the lower leg, protecting both – the tendon of quadriceps and the cartilage of the thigh bone¹. Another function of sesamoid bone is the redirection of the muscle's traction vector at the insertion point, so the muscle's action is more efficient. Specifically, the patella increases the efficacy of the quadriceps femoris during lower leg extension by about 40%².

¹ Grelsamer R, Weinstein C. Applied Biomechanics of the Patella. Clinical Orthopaedics and Related Research. 2001; 389:9-14.

² Wendt P, Johnson R. A study of quadriceps excursion, torque, and the effect of patellectomy on cadaver knees. The Journal of Bone & Joint Surgery, 1985, 67(5):726-732.

Download JPG image — The anterior, medial, and posterior view of the knee joint and patella.
Note that the patella's articular surface is not fully congruent to the thigh bone's patellar surface¹ and the contact area between femur and patella changes significantly during knee flexion-extension motions.².
The list of terms:
*Basis patellae* – Base of patella
*Apex patellae* – Apex of patella
*Facies anterior* – Anterior surface of the patella
*Facies articularis* – Articular surface

¹ Grelsamer R, Weinstein C. Applied biomechanics of the patella. Clinical Orthopaedics and Related Research. 2001; 389:9-14.

² Fox A, Wanivenhaus F, Rodeo S. The basic science of the patella: structure, composition, and function. The Journal of Knee Surgery, 2012; 25(02):127-142.

360° rotation of the right knee joint & the patella.

First published: 27/Oct/2020
Last update: 25/Nov/2020