Updated: Aug 13, 2018
Even if you don’t know what they are, you have probably seen them on foot radiographs and have wondered about them. They are one of most common things my patients point out on their own foot x-rays because they seem a little out of place. The structures I am referring to are called sesamoid bones (see x-ray at right). These are two small, pebble-like bones that sit underneath the 1st metatarsal head. It is normal to have them, but because of their location underneath the foot (being the ball of the foot), they are susceptible to injury and, if not treated in a timely manner, they can become a chronic issue. So, my goal with this post is to make you more aware of their existence and the symptoms that can be experienced when they become irritated or injured.
Underneath each first metatarsal bone there are two sesamoid bones. You can often feel them along the balls of your feet near the big toe joints. Several ligaments, as well as the short flexor muscle tendon to the big toe attach to them, while the long flexor tendon to the big toe travels between the bones before inserting into the distal toe bone.
CAUSES OF SESAMOID INJURIES
These bones are small and have to bear a lot of weight, which puts them at risk for injury. And with higher impact activities, such as running, when 3-4 times one’s body weight is put through the lower extremity, even more pressure is placed on these little bones. People with higher-arched feet are also at increased risk for injury because they put most, if not all, of their weight along the balls of their feet (where these bones are) and their heels.
When the sesamoid bones become inflamed and painful, it is called sesamoiditis. Too much pounding or trauma can even cause these bones to break, resulting in a sesamoid fracture (or sesamoid stress fracture). It is important to differentiate a fracture from a bipartite sesamoid, which is a normal variant, in which the sesamoid bone is in two pieces. An examination and x-ray by a doctor can help distinguish the two.
When the sesamoids are injured, the pain is typically felt directly underneath the involved sesamoid bone, which is along the ball of the foot. The pain will be worse when standing or doing higher impact activities. It will also likely be felt more when walking on harder surfaces, such as cement or hardwood floors compared to walking on grass or carpeted floors.
When treating sesamoiditis, it often comes down to offloading the sesamoid bones. This can be done with a dancer’s pad, made of felt, foam, or gel. The purpose of the pad is take pressure off the sesamoid bones and place it along the area surrounding them. If that isn’t enough, a walking boot may be required for a short period of time. Wearing good, supportive tennis shoes with cushion can help and avoiding barefoot walking, flat shoes, and flip-flops is important. Icing and anti-inflammatory medications can help with the inflammation and any swelling. Custom orthotics can also be made to help accommodate the area.
If the sesamoid bone is actually broken, this typically requires more protection, and sometimes even a period of being non-weightbearing. Bone fractures usually take about 6-8 weeks to heal. Because there is decreased blood supply around the sesamoid bones, though, they can take longer to healing than an average bony fracture elsewhere.
If the sesamoid bone does not heal, continues to be painful, and/or loses enough blood supply that it actually dies, surgical excision of the affected sesamoid may be required.
Sesamoid injuries, most notably sesamoid fractures, can become a debilitating problem, especially for high-level athletes. It is important to recognize them as soon as possible to avoid delay in treatment. A longer period of immobilization and rest from sports may be required, and if pain or problems persist, the sesamoid bone can be excised.
DISCLAIMER: The above information is meant for educational purposes only and should not be construed as medical advice. Please consult the doctor, or your own healthcare professional, should you have questions or concerns related to your health.