Sesamoid Bone

As we have learned, Sesamoiditis is caused by various stimulants that irritate the sesamoid bones as well as the tendons surrounding them.  It is important however to understand the Sesamoid Bones themselves.

Where is The Sesamoid Bone:  The sesamoid bone is found just behind the big toe joint and are typically small in size (the size of a jellybean).  The bones themselves are located just under the head of the first metatarsal bone.  There are two sesamoid bones in the foot, a medial sesamoid bone and a lateral sesamoid bone.  The picture below shows exactly where the medial sesamoid bone is located, you can now clearly see how it is situated just behind the joint of the big toe.

sesamoid bones

What Makes The Sesamoid Bone Special:  The human anatomy tells us that the sesamoid bones are embedded within tendons in the foot and a few other places in the body, namely the knee, and hand.  But what makes these little bones special is not their location, but their free standing nature.  The Sesamoid Bone rests within tendons, unlike other bones which are connected to their bone neighbors if you will.  Sesamoids are very interesting in this way.  The bone is found specifically in areas where a tendon travels over a joint.  Since this only happens in a handful of places, the need for sesamoid bones is generally remote.

The Purpose of the Sesamoid Bones:  So now we know what they are, and where they are, but what the heck do we need these little guys for?  Well, that’s a great question.  The sesamoid bones were designed to act as a fulcrum or a lever arm for the flexor tendons which surround them.  Tantamount to their job as a fulcrum, the sesamoid bones also act a as body guards to their surrounding tendons.  On top of protection, the sesamoids also serve to bolster the tendons’ effects from a mechanical perspective.  The mechanical job of the sesamoid bones rests in their ability to properly position to tendon just slight away from the center of the joint.  In doing this, the sesamoid bone effectively increases the moment arm of the joint tendon.  These amazing little bones also serve as a prevention method against the flattening of the tendon when joint tension increases during certain movement.  In doing so it helps the tendon create a consistent moment arm throughout the numerous tendon loads that are place on tendons within the normal range of motion.

So Why All The Bad Press: The issue with the sesamoid bones is their location.  As you can see above, they are situated in a high pressure area.  This simple fact, combined with their close proximity to the tendons that house them creates a perfect storm for inflammation and pain.  No fun.  Many factors lead to irritation, including the size of the bones themselves, the size of the patient, the age of the patient, certain activities and even shoe choices. If you feel pain in this area, you may want to stay away from high heeled shoes and look for something more comfortable and even keeled.

Furthermore, the location and size of the sesamoid bone makes it very difficult to treat.  Since its location forces the patient to use it while walking, it is very difficult to get the pain to subside with ease.  In minor cases, one might find that anti-inflammatory medications work very well in reducing the pain.  There are also straps that are used to hold the big toe from bending upward which is a common movement that irritates the sesamoid bone’s surrounding tendons.  Cushioned shoe soles can also be used to reduce the pain, but will work best in a lace up shoe with good stability.