Sesamoiditis is inflammation and pain of the sesamoid apparatus under the first metatarsal head.
Sesamoiditis occurs when repetitive or excessive pressure is placed on the sesamoid bones, eroding the dorsal cartilage and leaving the subchondral bone exposed. Increased pressure and stress at the sesamoids can be caused by an everted rearfoot which drives the medial forefoot into the ground, or an everted forefoot (forefoot valgus). Sesamoiditis pain is often intractable. Effective treatment should reduce stress on the sesamoids which will reduce the inflammatory response.
Clinical Goal for Orthotic Treatment
To transfer force off of the painful sesamoid(s) to decrease pressure on the sesamoid apparatus.
Sesamoiditis Prescription Recommendations
- Polypropylene Shell – semirigid with no distal bevel
- The lack of distal bevel increases the thickness of the distal edge of the orthosis. This transfers force from the metatarsal head to the 1st metatarsal neck and the lateral forefoot.
- Wide Width
- A wider width through the arch increases surface area under the arch, effectively reducing pressure on the metatarsal heads.
- Minimum Cast Fill
- Minimum cast fill creates an orthosis that conforms closely to the arch of the foot and shifts pressure proximally from the metatarsal heads to the arch area.
- Medial Skive – 2mm
- The medial heel skive creates a stronger supinatory moment arm around the subtalar joint (STJ) axis to reduce excessive subtalar joint (STJ) pronation and heel eversion
- Inversion – 3 degrees
- Inversion of the positive cast increases arch height shifting pressure from the first metatarsal head to the arch of the foot.
- EVA Cover to Toes
- Reverse Morton’s Extension
- Transfers pressure from the first metatarsal head and sesamoids to the other metatarsal heads.
Sesamoiditis is caused by increased ground reactive force (GRF) under the first metatarsal head resulting in inflammation and pain of the sesamoids. Orthoses designed to treat this condition should reduce pressure on the first metatarsal head by transferring pressure proximally to the metatarsal necks and/or laterally to the other metatarsal heads. ProLab clients can contact a Medical Consultant with questions about the treatment of this pathology.
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