Sesamoiditis
The Highlights
Sesamoiditis involves irritation (and pain) around the small sesamoid bones and the tendon they sit in under the 1st toe / ball of foot area.
Diagnosis is made through physical examination and sometimes diagnostic ultrasound.
Treatment involves offloading the area with foot orthoses (specialist insoles), footwear advice and occasionally the use corticosteroid injection therapy.
What is it and what are the symptoms?
Sesamoid bones exist in the body to act like a pulley that give tendons a mechanical advantage for moving joints. The patella (knee cap) is the largest and best known sesamoid bone in the human body but in this case we are discussing the 2 much smaller sesamoid bones we have under the ball of each of our big toes. Pub quiz question you can debate - often the foot is said to have 26 bones each; it's actually 28 if you count the sesamoids and, in our opinion, they should definitely count!
In sesamoiditis, irritation occurs around these bones and the tendon (flexor hallucis brevis) which they sit in, often resulting in an acute pain which we commonly see in dancers, runners and those doing sports with cutting actions like football or tennis.
There is generally a focus of pain under the ball/pad of the big toe (the sesamoids sit under your 1st metatarsal head). Occasionally in acute injury there may be swelling at the site too. Pain can be dull or sharp and is usually brought on by direct pressure to the area and bending of the big toe which will worsen with increased activity and reliably ease with rest.
Why does it happen?
Increases stress on the sesamoid and flexor hallucis brevis tendon will predispose you to this issues. Foot function and structure may be important: high arches may increase forefoot pressures and as can a stiff 1st ray (the bones making up the front portion of the medial/inner arch of your foot) which your Podiatrist can assess. Footwear like high heels and shoes with very little forefoot cushioning may also be an issue. There may even be risk factors to do with the development of your sesamoid bones which vary a lot from person to person; this can influence their size, position or even occasionally a total absence of one of them during childhood development.
What are the treatment options?
Imaging can be useful in the first instance to ensure we are dealing with a sesamoiditis. We employ diagnostic ultrasound in-house to aid this and also assess factors mentioned above like the size, position and normal development of these bones. In cases where we are suspicious of more serious issues like a sesamoid fracture we will refer you for other imaging, most likely X-rays.
Treatment then becomes about significantly offloading the forces underneath the sesamoids. In our experience, especially in people with high arches, this is a condition that is challenging to improve without the use of foot orthoses (specialist insoles) that we can design in clinic to achieve adequate offloading. Custom foot orthoses which we can make in-house or through our lab partner are particularly good at achieving this. We will also counsel on appropriate footwear to use in conjunction with these - the main takeaway here being shoes that do not have a large heel, do no bend very much in the forefoot and ideally have reasonable forefoot cushioning.
In cases of sesamoiditis that are particularly painful or not improving with other treatments, we can offer corticosteroid injection therapy - this is a very straightforward injection which we perform after first administering a local anaesthetic so there is minimal pain involved.
