The sesamoids are two small, pea-shaped bones embedded within the flexor tendon beneath the great toe joint. They function as pulleys for the flexor hallucis longus tendon and bear significant compressive load during walking and push-off. Sesamoiditis is inflammation of the sesamoids and surrounding tissues without discrete fracture, while a sesamoid stress fracture is a small crack caused by repetitive overload — both are common causes of pain under the ball of the foot at the great toe.
Sesamoid injuries produce forefoot pain that can overlap with other conditions. A plantar plate tear affects the adjacent second metatarsophalangeal joint and can coexist, and Morton's neuroma produces interdigital pain in the same forefoot region. In athletes with forefoot pain, Freiberg disease of the lesser metatarsal heads is an additional diagnosis to consider.
Causes
Repetitive overload
Activities involving repeated forefoot loading and push-off — running, dancing (especially ballet), basketball, and martial arts — place high cyclic stress on the sesamoid bones. Sudden increases in training intensity, particularly in runners returning from a break, frequently precipitate acute symptoms.
Biomechanical and anatomic factors
High arches (cavus foot), a plantarflexed first ray, and altered gait mechanics concentrate pressure under the first metatarsal head and sesamoids. Tight, narrow, or high-heeled footwear shifts body weight onto the forefoot. Approximately 10–30% of people have a bipartite sesamoid — a sesamoid naturally divided into two segments — which can be more susceptible to stress injury and is frequently mistaken for a fracture on X-ray, making MRI essential for accurate diagnosis.
Direct trauma
A direct blow or landing impact to the bottom of the great toe joint can cause acute sesamoid fracture. Though less common than stress injuries, acute fractures may be associated with plantar plate disruption and require careful imaging evaluation.
Symptoms
Patients describe pain directly under the great toe joint — at the ball of the foot — that worsens with weight-bearing and particularly during the push-off phase of walking or running. Onset is typically gradual with sesamoiditis and tendinopathy, but more acute and sudden with stress fracture. Swelling, bruising, and difficulty passively or actively bending the great toe upward may also be present. A characteristic adaptive gait pattern develops in which patients walk on the outer edge of the foot to offload the painful sesamoid.
Diagnosis
Physical examination reveals point tenderness directly over the medial or lateral sesamoid, reproduced by direct palpation from the plantar surface and worsened by passive dorsiflexion of the great toe (which loads the sesamoid-tendon interface). X-rays are obtained first but have important limitations — distinguishing a stress fracture from a bipartite sesamoid is frequently impossible on plain films, as both appear as a divided bone.
MRI is the definitive study for sesamoid injuries and resolves the bipartite versus fracture dilemma reliably: a stress fracture shows bone marrow edema across the fracture line on fluid-sensitive sequences, while a bipartite sesamoid typically shows no edema unless acutely injured. MRI also identifies avascular necrosis — a serious complication in which the sesamoid loses its blood supply and undergoes fragmentation — and evaluates the flexor tendon and plantar plate for associated soft tissue injury. This comprehensive tissue characterization makes MRI the single most valuable study in persistent or atypical sesamoid pain.
Classification
Sesamoid disorders are categorized by underlying pathology:
- Sesamoiditis: Inflammation of the sesamoid and surrounding soft tissues without discrete fracture. The most common presentation; responds well to offloading and conservative care.
- Stress fracture: Microscopic or visible fracture from repetitive overload. Requires more aggressive offloading and longer recovery than sesamoiditis.
- Acute fracture: Discrete fracture from direct trauma or landing impact. May involve displacement requiring surgical assessment.
- Avascular necrosis: Loss of blood supply leading to progressive bone death, fragmentation, and collapse. The most serious complication, often requiring surgical excision.
Treatments
Treatment is almost always conservative, though healing can be protracted due to the limited intrinsic blood supply to the sesamoids and the challenge of fully offloading them during weight-bearing.
Initial conservative treatment:
Activity modification away from forefoot-loading activities, ice, and NSAIDs form the foundation of early management. Offloading is the key intervention — a stiff-soled shoe, a dancer's pad (a donut-shaped pad that surrounds the sesamoid without directly contacting it), or a custom orthotic with a sesamoid cutout all effectively redistribute pressure away from the painful bone. A walking boot provides more complete offloading during acute flares.
Confirmed stress fracture — extended immobilization:
Non-weight-bearing in a short leg cast for 4–8 weeks is often required for confirmed stress fractures, particularly those with significant bone marrow edema on MRI. Bone stimulator devices may be used as an adjunct to accelerate healing. Platelet-rich plasma (PRP) injections have shown promise in facilitating tendon and bone healing in refractory cases. Return to sport is gradual and guided by resolution of symptoms and MRI findings.
Surgical treatment (refractory cases only):
Surgery is considered only after 6–12 months of failed conservative management, or for confirmed avascular necrosis with fragmentation. Partial or complete sesamoidectomy (surgical removal of the affected sesamoid) reliably eliminates pain but carries the trade-off of altered great toe biomechanics — removal of the medial sesamoid can cause hallux valgus drift, and removal of the lateral sesamoid can cause hallux varus. Surgical planning must account for these biomechanical consequences.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Foot and Ankle MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.