What are they?

Sesamoids are bones found within tendons.  They often are found where tendons pass over joints.  An example is the tendon found under the big toe which has two sesamoids. Problems with these sesamoids are uncommon but when they arise it can be very disabling.

What can go wrong?

The sesamoid bones under the big toe can become painful for a number of reasons.  They can fracture, the blood supply can be damaged and they can fragment, they can develop arthritis with the metatarsal and the bursa (fluid filled sac) under the sesamoids can become inflamed and swollen.

How is it diagnosed?

Careful clinical examination will reveal pain and tenderness under the big toe joint. Other foot deformities which might be causing the problem will be excluded. X-rays are a good first line investigation. If more information is required a bone scan or an MRI scan will be requested.

What are the treatments?

If an underlying cause is identified (e.g. repetitive strain injury) then activity modification will be necessary.  It is also helpful to offload the painful sesamoid and this can usually be achieved with a custom made insole.  Sometimes a plaster and crutches are needed to fully rest the foot.  It is unusual to need surgery but if these treatments fail then the sesamoid may need to be removed.