Pain under the big toe joint can have many causes, although one common cause is unique to the anatomy of the big toe joint itself. Inflammation of two small, unique bones called sesamoids can cause significant pain under this joint. This article will discuss the condition known as sesamoiditis, and the treatment options available.
Sesamoiditis is generally unique to the big toe joint, as this is the only part of the foot where these bones consistently appear. The word sesamoid is used to describe a round or oval shaped bone found outside the usual connected skeleton. Several extra foot bones that appear in some humans are sometimes called ‘sesamoid’ bones. However, true anatomic sesamoid bones found in all humans are the consistently appearing bones found under the big toe joint. These two small, egg-shaped bones about the size of a peanut M&M candy sit under the big toe joint, and fit within two shallow grooves formed on the bottom of the first metatarsal head, the long bone that forms the first part of that joint. Sesamoids can appear as complete bones, or can form after birth in two or three separate pieces. Serving in an assisting role in bearing weight across the big toe joint during foot push-off, as well as a stabilizer for the various structures that cross over and around the big toe joint, the sesamoids bear a great deal of weight and stress during walking and running. Injury to these bones can happen on an acute and chronic basis.
Acute injury to the sesamoids can happen due to a variety of reasons. These include falling from a height onto the ball of the foot, crushing injuries to the big toe joint, directly kicking an object that forces the big toe upwards, or a direct blow to the bottom of the foot. Chronic injuries to the sesamoids can take place during repetitive pressure on the ball of the foot from activities such as dancing or stair climber use. This can also be seen in repetitive work-related activities, such as pedal use in machinery or platform standing. Indirect force from abnormal pulling of the tissue that attaches near or on the sesamoids can also lead to injury. In general, only one of the two sesamoids usually becomes injured, as injury to both is possible but uncommon.
Symptoms of sesamoiditis can include a sharp pain or dull ache on the bottom of the big toe joint. This pain becomes worsened when the toe is flexed in an upwards direction. Any activity that stresses this joint, including walking, running, and jumping, can cause pain. This is especially true while one is barefoot. Using flat and supportive shoes helps to decrease the the pain of this condition, while high heels makes it worse. The tissue under the big toe joint may feel swollen or full, and may even be warm to the touch in less common cases.
This condition is typically diagnosed during a simple physical exam by a foot specialist, although x-rays may be needed to rule out a stress fracture of true fracture. Stress fractures of the sesamoids can mimic the symptoms of sesamoiditis, and may be difficult to diagnose properly as they may not show up early on the x-ray. Special imaging like an MRI or nuclear bone scan is often needed to confirm a stress fracture. True fractures are typically easy to find on an x-ray, however the presence of a sesamoid in several pieces may not always be distinguishable from a naturally occurring multi-piece sesamoid that is simply inflamed. A physician must evaluate the nature of the line between the pieces to determine if it is a fracture or simply a natural separation.
Treatment of sesamoiditis can be difficult at times, as healing may be slow. The basic treatment course involves removing the inflammation, and reducing the stress that caused it in the first place. Inflammation can be reduced by using anti-inflammatory medications. Icing is also an important part of this treatment course. More direct intervention can be considered in stubborn cases: if no fracture or stress fracture is suspected, a steroid injection can be given to reduce the inflammatory reaction of the bone and its surrounding region. These measures address the inflammation causing the pain, but the underlying stress also needs to be reduced for proper healing. This is made possible by using offloading padding or specialized shoe inserts to reduce pressure under the ball of the foot, or by modifying the activity that caused it in the first place. The use of stiffer-soled shoes is usually necessary, and impact activities must be curtailed during the healing process.
More serious cases may require immobilization in a walking boot or in a cast for up to several months. Cases that simply won’t heal with any of these measures may require surgical intervention. Surgical removal of one of the sesamoids is typically effective at eliminating the pain, and is sometimes also necessary when stress fractures or true fractures won’t heal. However, it should be noted that most people recover uneventfully and don’t need surgery or prolonged immobilization. Dancers and athletes can return to activity once the condition resolves, but with the knowledge the condition may return if stress to the big toe joint continues. The same applies for those with repetitive foot tasks at work.
Sesamoiditis can potentially be a long-term condition if not treated properly and promptly, and is often mistaken for other general big toe arthritic conditions with inadequate treatment the result. This common foot problem is easily treated, although the time to full healing may be somewhat lengthy. By seeing a foot specialist when the symptoms begin, a speedier recover can be potentially achieved, avoiding months of pain and disability.