Sesamoids are small bones embedded within tendons that are typically found in several joints of the body.
In the foot, the tibial and fibular sesamoid bones are located in the medial and lateral heads of the flexor hallucis brevis tendons, within the articular capsule of the first metatarsophalangeal joint.
This hallux sesamoid complex serves to stabilise the first metatarsophalangeal joint in propulsion and to elevate the first metatarsal head to facilitate the optimal distribution of weight forces to the lateral aspect of the forefoot.
With a significant amount of force being consistently transmitted through the sesamoid bones, these hallucal sesamoids can become susceptible to a host of injuries resulting from shear and loading forces.
Certain physical activities increase the pressure on the forefoot and multiply these forces. For instance, forces equivalent to three times an individual’s bodyweight pass through the sesamoids while running. This considerably strains the medial sesamoid, which bears the maximum amount of this force, causing immense pain and discomfort.
A dysfunctional foot posture reduces the efficiency of the arches of the foot in absorbing the shock forces generated upon heel strike.
The repetitive stress resulting from such postural discrepancies increase the risk of injury and inflammation to the sesamoid bones.
The same is true in the case of a hyperpronated foot, which causes excess pressure to be placed on the hallux and the first metatarsal head, over-stressing the sesamoid bones in the process.
Sesamoid injuries are diagnosed by conducting a physical examination to check for tender spots in the affected region. This is done either by directly pressing the bone or by asking the patient to bend or straighten the hallux.
X-rays of the forefoot may be conducted to ensure there are no fractured sesamoids. A bone scan or MRI may also be performed to clearly differentiate between sesamoiditis and a fracture.
A detailed biomechanical assessment of the feet would help in spotting any postural problems, which need to be considered while devising an appropriate treatment plan.
The inflammatory nature of the condition makes it necessary to reduce the inflammation first, by avoiding physical activities that could potentially flare-up the affected sesamoids more. This needs to be followed by the application of ice packs and the use of non-steroidal anti-inflammatory medications, if necessary and as recommended by a clinician.
Long-term treatment for the condition can involve the use of supportive foot devices to stabilise the foot by supporting it in its optimal posture. This promotes the normal distribution of pressure in the foot, and the sesamoids are no longer compressed due to excessive weight under the hallux and the first metatarsal head.
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Repetitive plantarflexion can lead to pain and mechanical limitation in the posterior ankle joint which is known as posterior ankle impingement syndrome. This pathology commonly occurs in ballet dancers and football players.