Sesamoid Injury and Sesamoiditis

Most patients present with insidious-onset pain under the head of the first metatarsal, worse on push-off, hill work, sprinting, or wearing rigid shoes. Pain may radiate dorsally or into the hallux. An acute fracture or turf-toe variant produces sudden pain following hyperextension or direct trauma.

Examination:

• •Localised tenderness directly over the affected sesamoid (medial or lateral plantar to the first metatarsal head) is the highest-yield sign. Differentiate from joint-line first MTP tenderness
• •Pain on passive dorsiflexion of the hallux (loads the sesamoid complex)
• •Pain on resisted plantarflexion of the hallux
• •Pain on single-leg heel raise with weight on the first ray
• •Antalgic gait, often offloading to the lateral forefoot
• •Range of motion at the first MTP usually preserved unless there is significant turf toe or hallux rigidus
• •Assess plantar digital nerve symptoms (paraesthesia, altered sensation, neuritic pain) to exclude digital nerve entrapment as a mimic

Differential diagnoses: bipartite sesamoid (smooth corticated edges on X-ray, commonly bilateral, non-tender); acute sesamoid fracture (sudden pain on direct blow or hyperextension; sharp irregular fracture line); turf toe (plantar plate/capsular injury after acute hyperextension - swelling, loss of push-off); hallux rigidus (dorsal joint-line tenderness, reduced dorsiflexion, dorsal osteophyte); gout of the first MTP (acute red, hot, exquisitely tender joint - aspirate for crystals); flexor hallucis longus tenosynovitis (pain along FHL course, often with triggering or catching, classic in dancers); sesamoid chondromalacia (chronic plantar first MTP pain, MRI diagnosis); digital nerve entrapment.

Turf toe is a plantar plate/capsuloligamentous injury of the first MTP after forced hyperextension. Sesamoid fracture, retraction, diastasis, or proximal migration suggests a higher-grade injury and should prompt specialist assessment.

Plain radiographs are first-line. Request weight-bearing AP, lateral, and oblique views where the patient can tolerate them, plus a dedicated sesamoid axial (skyline) view. Weight-bearing views are essential for assessing subtle joint space narrowing, diastasis, and arch position that disappear when the foot is unloaded. Compare with the contralateral foot when bipartite versus fracture is uncertain. A negative or equivocal X-ray does NOT exclude pathology - acute and stress fractures can be radiographically silent for several weeks.

MRI is the preferred next investigation when X-rays are negative or equivocal. It demonstrates bone marrow oedema (sesamoiditis or stress reaction), cortical breach (fracture), avascular necrosis (low T1, variable T2 signal), and associated plantar plate or capsular injury. No radiation - important in young athletes.

CT is particularly useful when the key question is cortical fracture, bipartite sesamoid versus fracture, fragment morphology, articular irregularity, delayed union, or surgical planning. BOFAS notes CT is highly sensitive and specific for fracture identification.

Bone scan is sensitive but non-specific and is largely superseded by MRI.

Investigate underlying contributors as guided by history: vitamin D, calcium profile, RED-S assessment in young athletes (using the IOC REDs CAT2 clinician-facing tool for risk stratification and return-to-sport decisions), and footwear or biomechanical review.

The mainstay is offloading and activity modification, with progression to surgical referral only after a sustained trial of conservative care or for specific high-risk indications.

First-line conservative management (sesamoiditis or undisplaced stress reaction without fracture):

• •Activity modification: stop the offending impact loading; cross-train (cycling, swimming, deep-water running)
• •Footwear: stiff-soled or rocker-bottom shoes, well-cushioned trainers; avoid heels and rigid forefoot
• •Sesamoid offloading: dancer pad, metatarsal pad, full-length custom orthotic with sesamoid relief (cut-out behind the first metatarsal head), or rigid carbon fibre insole / Morton extension to prevent first MTP dorsiflexion
• •Analgesia: simple analgesia and short-course NSAIDs per BNF guidance, with appropriate GI and cardiovascular caution
• •Local steroid injection: avoid routinely in acute sesamoid pain, especially before fracture, plantar plate injury, or AVN has been excluded. Potential risks include fat-pad atrophy, soft-tissue weakening, and symptom masking. Consider only in selected refractory inflammatory cases under image-guided specialist care

Address modifiable factors: footwear, training load, biomechanics, RED-S, bone health (vitamin D, calcium). Symptoms may improve over several weeks with strict offloading, but recovery can be prolonged where there is stress fracture, chondral pathology, bipartite disruption, or osteonecrosis.

Sesamoid stress fracture or acute fracture (undisplaced) per BOFAS pathway:

• •Non-weight-bearing cast with toeplate (or equivalent strict immobilisation) for around 6 weeks
• •Walking boot for around 6 weeks
• •Then stiff-soled shoe or orthotic depending on symptoms and imaging

Healing is often slow due to the relatively hypovascular distal blood supply, with non-union rates around 30 percent reported. Re-image at intervals to assess healing. VTE risk assessment per NICE NG89: consider LMWH or fondaparinux for lower-limb immobilisation when VTE risk outweighs bleeding risk; consider stopping if immobilisation continues beyond 42 days.

Surgical referral indications: failed conservative management beyond 3 to 6 months; established non-union or delayed union; avascular necrosis with progressive symptoms; displaced fracture or symptomatic bipartite diastasis; recurrent or chronic pain limiting function.

Surgical options include partial sesamoidectomy (preserving as much sesamoid as possible to maintain flexor hallucis brevis function), bone grafting with internal fixation for selected non-unions, or complete sesamoidectomy when bone is unsalvageable. Removing both sesamoids should be avoided where possible: complete excision of the medial sesamoid risks hallux valgus; complete excision of the lateral sesamoid risks hallux varus; excision of both risks cock-up deformity and major loss of first MTP function.

Rehabilitation runs in phases with timeline driven by symptom resolution and (for fractures) imaging evidence of healing.

Phase 1 (offloading and symptom control, weeks 0 to 6 to 8): activity modification, sesamoid offloading orthotic or carbon fibre plate, footwear review; cast or boot immobilisation if fracture. Maintain cardiovascular fitness with non-impact work (cycling, swimming, deep-water running).

Phase 2 (protected loading): progressive return to walking once tenderness improves; hallux range of motion (avoiding aggressive forced dorsiflexion early); intrinsic foot strengthening, calf and tibialis posterior conditioning; continue orthotic offloading.

Phase 3 (graduated impact): walk-jog progression once weight-bearing is symptom-free; plyometric and sport-specific drills delayed until pain-free hopping and heel raise.

Phase 4 (return to sport): sport-specific reconditioning; continue orthotic and footwear modifications long-term in many cases to reduce recurrence.

Address upstream contributors throughout: training load, footwear, biomechanics (cavus foot, plantarflexed first ray), and bone health (vitamin D, RED-S).

• •BOFAS Hyperbook: Sesamoid Disorders - UK specialist consensus on diagnosis, imaging, and the 6-week non-weight-bearing then 6-week boot conservative pathway for undisplaced sesamoid fractures.
• •IOC REDs CAT2 (Mountjoy et al., BJSM 2023) - the standard framework for assessing Relative Energy Deficiency in Sport in any young athlete with a high-risk stress injury including the sesamoids.
• •NICE NG89 - VTE risk assessment is required in lower-limb immobilisation, with pharmacological prophylaxis considered when VTE risk outweighs bleeding risk.
• •BNF NSAIDs treatment summary - short-course analgesia framework for primary care management, with appropriate GI and cardiovascular caution.
• •Coughlin and Mann textbook of foot and ankle surgery - the standard reference for surgical decision-making, including the recognised risks of medial sesamoidectomy (hallux valgus) and lateral sesamoidectomy (hallux varus).

• •Classic patient: runner, dancer, footballer, or military recruit with insidious plantar pain at the first MTP, worse on push-off. Sesamoiditis is a generic term covering stress reaction, fracture, bipartite disruption, chondromalacia, and AVN - persistent symptoms need imaging.
• •The medial (tibial) sesamoid is more commonly affected because it bears greater load. A bipartite sesamoid is present in 10 to 30 percent of feet and is commonly bilateral; smooth, sclerotic, corticated edges distinguish it from a sharp, irregular fracture line - compare with the contralateral foot.
• •Weight-bearing AP, lateral, and oblique foot films plus a sesamoid axial (skyline) view is the standard plain-film series. A negative X-ray does NOT exclude a stress fracture; MRI for marrow oedema and AVN, CT for fracture line and fragment morphology.
• •Conservative care first: activity modification, stiff-soled or rocker-bottom shoes, sesamoid offloading orthotic or Morton extension. Avoid routine local steroid injection before fracture, plantar plate injury, or AVN has been excluded.
• •BOFAS pathway for undisplaced stress or acute fracture: non-weight-bearing cast with toeplate for 6 weeks, then walking boot for 6 weeks, then stiff-soled shoe or orthotic. Non-union rates around 30 percent due to the relatively hypovascular blood supply.
• •Surgery for failed conservative care beyond 3 to 6 months, non-union, AVN, displaced fracture, or symptomatic bipartite diastasis. Partial sesamoidectomy is preferred over complete. Medial excision risks hallux valgus; lateral excision risks hallux varus; bilateral excision risks cock-up deformity.