The Sesamoid Bones

sesamoid bonesFor assorted reasons there are a number of places in the body where muscle in and of itself is not enough to accomplish a given task. The sesamoid bones, like the tendons of the rectus abdominis (crunches muscle), the IT band, and the pulley systems of the ankle, knee, and the psoas, are the body’s way of maximizing efficiency within the system.

Sesamoid bones are bones set into tendons which increase the leverage and strength of their associated muscle.  Occurring around joints, they also act to minimize friction and facilitate gliding. Though they are found in numerous parts of the body, the patella, or knee cap, is our most prominent sesamoid bone.

You can easily see and feel the kneecap which is embedded into the tendon of the quadriceps muscle. The quadriceps functions to stabilize the knee in extension which is a lot to ask of a very long muscle group. The quadriceps is four muscles that reach from the pelvis to below the knee. In addition to stabilizing the knee the quadriceps also acts as a hip flexor. The presence of the entrenched patella makes the muscle more powerful and effective.

While they are also found in the hands most pain issues relate to the feet where two sesamoid bones are inserted into the flexor hallucis brevis allowing the muscle to have greater force and a larger range of motion. These bones are on the underside of the foot and are easily injured, often from the blunt force of jumping. The flexor hallucis brevis flexes the big toe joint and you can’t imagine the number of people I see who can’t move their big toes on command.

Bunions occur when the big toe for whatever reason gets pulled out to the side taking the flexor hallucis brevis and its sesamoid bones along with it. I think that the distinction between bunions with and without pain lies in the effects of the big toe’s pull on the sesamoid bones.

The trouble that arises with the sesamoid bones in any part of the body, but especially the feet, is almost always due to mechanical dysfunction. The posts for the last few days about hyperextension of the knees and the angles ideally created by the bones of the lower leg directly relate to this post. Misalignment and poor mechanics put a major strain on the sesamoid bones and can hamper any productive use of the body.


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