Sesamoid Disorders of the Foot

Hallucal sesamoid pathology runs from a benign anatomical variant, the bipartite sesamoid, to conditions disabling enough to need surgery, such as AVN and nonunion. Exam scenarios turn on the differential diagnosis and the imaging that separates it.

Who. Athletes, dancers and runners are most affected, typically aged 20-40 for acute injuries, and men and women are affected equally. The activities that bring them in:

• Ballet - the relevé position
• Running - the push-off phase
• Basketball - jumping

High heels, cleats or minimalist shoes increase forefoot loading.

Risk factors.

• Cavus foot - rigid, with a peaked MTPJ angle
• Plantarflexed first ray
• Gastrocnemius tightness - the equinus prolongs forefoot loading
• Training errors - a sudden increase in volume, hard surfaces
• Previous sesamoid pathology, which increases the risk of reinjury

The complex. The hallucal sesamoids are two small ovoid bones embedded within the tendons of flexor hallucis brevis (FHB), plantar to the first metatarsal head. The dorsal surface of each articulates with the crista on the plantar metatarsal head; the plantar, non-articular surface gives attachment to the plantar plate and FHB. Six soft-tissue structures relate to them, and their attachments explain both the injuries and the deformities that follow excision.

Tibial and fibular. The tibial sesamoid carries more of the load and is far more often the one that fractures. Which of the two is removed decides the direction of any drift that follows.

Blood supply. The sesamoids are supplied from the first plantar metatarsal artery (Rath 2009). Sobel's injection study found two major entry sources, proximal at the FHB attachment and plantar near the midline, with a minor distal contribution, and both sesamoids equally well vascularised. The watershed pattern means distal pole and mid-substance fractures can compromise perfusion and predispose to avascular necrosis and nonunion; at surgery, the proximal and plantar surfaces should be respected to preserve it.

Function. The sesamoids do four jobs in the first ray:

1. Mechanical advantage - they lift the FHB tendon away from the joint centre and increase its moment arm
2. Load absorption - 2-3 times body weight in walking, up to 300% during running
3. FHL protection - they elevate the metatarsal head and shield the FHL tendon from compressive forces
4. Weight distribution - they spread force across the metatarsal head during gait

The windlass. At toe-off, hallux dorsiflexion tightens the plantar fascia, raising the arch and depressing the first metatarsal head, which greatly increases the force transmitted through the sesamoid complex. Any pathology that makes the sesamoids painful disrupts this mechanism, and the compensatory gait changes can lead to transfer metatarsalgia.

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Overuse. Sesamoiditis is an inflammatory response to chronic repetitive loading. In athletes who repeat toe-off, in ballet, running and jumping, cumulative microtrauma exceeds the tissue's healing capacity, and the result is:

• Bone marrow oedema visible on MRI
• Periosteal inflammation
• Soft-tissue swelling in the FHB tendons and plantar plate
• Bursitis between sesamoid and metatarsal head

Stress fracture. When cyclical loading exceeds the bone's capacity to remodel, a stress fracture develops through a predictable sequence:

1. Stress reaction - increased osteoclastic activity creates microscopic trabecular damage
2. Cortical disruption - a fracture line appears as remodelling fails to keep pace
3. Propagation - continued loading extends the fracture through the cortex
4. Displacement - in severe cases, a complete cortical break with fragment separation

Acute fracture. High-energy axial loading (forced dorsiflexion, direct impact) exceeds the bone's ultimate tensile strength and fractures it at once. How far it displaces depends on the magnitude of the force and the integrity of the surrounding soft-tissue envelope.

Why the tibial sesamoid. It is the more frequently injured of the two, and the reason is mechanical: it sits directly beneath the first metatarsal head in the line of weight transfer and carries the larger share of the load. Its larger size creates greater stress concentration, and first ray plantarflexion drives it into ground contact. Sobel found both sesamoids equally well vascularised, so the widely repeated claim that the tibial sesamoid has a poorer blood supply is not supported; what determines AVN risk is where the fracture line sits relative to the proximal and plantar vascular entry points, not which sesamoid it is.

Avascular necrosis. AVN develops when the blood supply is critically compromised, most commonly by:

• Fracture - distal pole fractures disrupt the proximal vascular pedicle
• Idiopathic - gradual vascular insufficiency from chronic repetitive trauma
• Surgery - excessive soft-tissue stripping

The sequence then runs from osteocyte death, through failed repair in persistently ischaemic bone, to subchondral collapse as necrotic bone gives way under load. Fragmentation and sclerosis follow as the body attempts to revascularise, and secondary degenerative change develops in the metatarsosesamoid joint.

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Arthritis. Chronic overload or post-traumatic change degrades the cartilage of the metatarsosesamoid articulation. Progressive joint-space narrowing, osteophyte formation and subchondral sclerosis follow the usual osteoarthritic pattern.

Why they heal poorly. The blood supply is limited and the loading constant during walking. The bone is small, which limits revascularisation, it sits embedded in a tendon that creates shear forces across it, and its plantar soft-tissue coverage is poor.

Classification is descriptive, by aetiology and imaging, along a continuum from normal variant to surgical condition.

History. Onset and mechanism usually point to the pathology. Insidious onset suggests sesamoiditis or a stress fracture, and acute onset a traumatic fracture or turf toe. Forced dorsiflexion points to turf toe, repetitive push-off to sesamoiditis and a single impact to an acute fracture. The pain is localised plantarly and worse in the toe-off phase of gait, and prior episodes suggest chronic overload or a bipartite variant.

Look. Examination localises the pathology and rules out the differential.

• Swelling - mild plantar MTPJ oedema suggests active inflammation
• Erythema - may indicate gout, infection or acute injury
• Callosities - an intractable plantar keratosis (IPK) under a sesamoid indicates prominence
• Alignment - cavus foot, hallux valgus or first ray plantarflexion
• Gait - antalgic, with a shortened stride and early heel rise to avoid push-off

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Feel.

• Point tenderness - direct pressure over the specific sesamoid reproduces the pain
• Dorsal or plantar - make sure the pain is plantar (sesamoid), not dorsal (arthritis, gout)
• Joint line - palpate the MTPJ for synovitis or effusion
• FHL excursion - pain with FHL gliding suggests tendinitis
• Neurovascular - sensation (medial plantar nerve) and pulses

Provoke.

• Passive dorsiflexion test - extending the hallux while palpating the sesamoid reproduces pain by loading the complex
• Resisted flexion - active flexion against resistance tests FHB and FHL integrity
• Push-off test - inability to perform a single-leg heel raise indicates significant pain
• Grind test - compression plus rotation reproduces arthritic pain
• Vertical Lachman - dorsal translation indicates plantar plate injury (turf toe)

Differential diagnosis of sesamoid pain. Turf toe aside (see Classification):

• Trauma - acute fracture, or stress fracture from repetitive loading
• Inflammation - sesamoiditis from overuse, bursitis, gout
• Symptomatic bipartite sesamoid - usually asymptomatic, but the synchondrosis can be painful
• Infection - osteomyelitis (rare) or septic arthritis
• Arthritis or AVN

Radiographs first. Weight-bearing films in three views:

• AP foot - sesamoid alignment, fracture diastasis, bipartite margins
• Lateral foot - sesamoid height and proximal migration (turf toe)
• Axial (skyline) sesamoid view - critical for visualising the sesamoid-metatarsal articulation

Always obtain bilateral comparison radiographs to check a two-part sesamoid for symmetry. AVN shows as sclerosis, fragmentation, collapse and loss of height; arthritis as joint-space narrowing, osteophytes and subchondral cysts.

Bipartite or fractured. This is the distinction the films must make. A bipartite sesamoid is a congenital variant, present in 10-30% of the population, and the tibial sesamoid is 10 times more likely to be bipartite than the fibular. A fracture has a sharp, irregular line, is unilateral and shows bone marrow oedema on MRI. Five features point to a bipartite variant instead:

1. Smooth, rounded corticated margins, against a sharp jagged fracture line
2. Bilateral symmetry - present in both feet in 85% of cases
3. Larger total volume - the fragments together exceed a normal single sesamoid
4. Unequal fragment sizes - typically one large and one small piece
5. Normal MRI signal - no bone marrow oedema unless the synchondrosis is symptomatic

If unsure, MRI is definitive: a fracture shows surrounding oedema, and a bipartite sesamoid does not unless it is symptomatic. An asymptomatic bipartite sesamoid needs no treatment.

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MRI. The gold standard for sesamoid pathology, and the definitive test when radiographs are normal or equivocal.

• T1 - low signal indicates oedema, AVN or chronic change
• T2/STIR - high signal confirms acute bone marrow oedema
• Proton density - cartilage integrity and the plantar plate

Each diagnosis has its pattern:

• Sesamoiditis - bone marrow oedema, intact cortex, normal FHB and plantar plate
• Stress fracture - linear T2 hyperintensity, surrounding oedema, cortical disruption
• AVN - low T1 and T2 signal (sclerosis), fragmentation, subchondral collapse
• Symptomatic bipartite - oedema at the synchondrosis; an asymptomatic one shows normal signal
• Turf toe - plantar plate rupture, capsular tear, joint effusion, sesamoid retraction

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CT and bone scan. CT is best for assessing fracture healing (union or nonunion), bony architecture and surgical planning. A bone scan has high sensitivity for stress reactions and sesamoiditis but low specificity, and is the fallback if MRI is contraindicated.

Indication. A painful plantar prominence or intractable plantar keratosis under the tibial sesamoid, with a preserved metatarsosesamoid joint and no fracture, AVN or arthritis: the problem is mechanical prominence, not intra-articular disease. It is the least destructive surgical option and preserves the sesamoid and the FHB.

Technique. Through a medial or plantar-medial approach the sesamoid is exposed within the FHB without shelling it out. A burr or osteotome shaves the plantar (non-articular) half flush, reducing the prominence while leaving the dorsal articular surface and the FHB attachment intact. Because the FHB is not divided, the flexor mechanism and the medial buttress are preserved, avoiding the hallux valgus and cock-up risks of total excision.

Endoscopic shaving. A medial portal and blunt plantar dissection establish access, fluoroscopy controls resection of the plantar half with an abrasion burr, and endoscopy confirms a smooth residual surface without FHL injury.

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Aftercare and pitfalls. Offloading is similar to the non-operative protocol, with an earlier return than after excision. The main risks are inadequate debridement (persistent keratosis), fracture of the thinned sesamoid and violation of the articular surface. Shaving does not help if the pain is intra-articular (arthritis or AVN), where excision is required.

Unloading osteotomy. A plantar prominence of the first metatarsal head can instead be addressed with a dorsoproximal sliding osteotomy, which unloads the sesamoid complex without excising it; overcorrection risks transfer metatarsalgia.

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What it is. Removal of only the diseased fragment of a sesamoid, typically the smaller, avascular or ununited pole, while retaining the viable fragment and the FHB attachment. It is used for a fractured or symptomatic bipartite sesamoid where one pole is diseased, or for a stress-fracture nonunion of a bipartite sesamoid, most often as the proximal-fragment excision described for medial (tibial) sesamoid stress fractures.

Why it helps. Preserving the larger viable pole and the FHB maintains more of the flexor lever and the medial or lateral buttress than total excision. That reduces the risk of hallux valgus or varus and cock-up deformity while still removing the pain source, a middle option between planing and total sesamoidectomy.

When it is enough. Only when one pole is clearly the pain source and the retained pole is viable; if the whole sesamoid is necrotic or arthritic, total excision with FHB repair is required. Biedert and Hintermann excised the proximal fragment in young athletes with medial sesamoid stress fractures, and all were pain-free and back to full sport within six months.

How often. Published series report:

• Overall satisfaction 85-95% at 2-year follow-up
• Hallux valgus or varus 5-15% (reduced with modern repair techniques)
• Cock-up toe 5-10% (preventable with FHB repair)
• Transfer metatarsalgia 10-20% (managed with orthotics)
• Neuroma 5% (nerve protection critical)

Shimozono's systematic review, in the Evidence Base, found an overall complication rate of 22.5%, although the mean hallux valgus angle did not change significantly. The key to minimising complications is meticulous technique, with emphasis on preserving and repairing the FHB tendon.

After bone grafting. Rehabilitation is stricter and return to sport slower than after sesamoidectomy:

• Strict non-weight-bearing for 8 weeks in a short leg cast or boot
• Radiographs at 6 and 12 weeks to confirm union
• A weight-bearing boot from week 8 to 12
• Full weight-bearing by 12 weeks if healed
• Return to sport at 6-9 months

Global Epidemiology

• Population at risk: Predominantly athletes and dancers worldwide. Sesamoid injuries account for roughly 9% of foot and ankle injuries in athletic populations and up to 12% of great-toe injuries.
• Sport distribution (international): Running and sprinting (push-off loading), ballet and dance (relevé), football/soccer and rugby (forced dorsiflexion), basketball and gymnastics (jump landings), and cricket fast bowling (repetitive forefoot impact).
• Bipartite prevalence: 10-30% of the general population; bilateral in around 85%; tibial sesamoid roughly 10 times more likely to be bipartite than fibular.
• Fracture distribution: Tibial-to-fibular fracture ratio approximately 25:1, reflecting greater medial load-bearing.

Side-by-Side Society Guidance

There is no dedicated AAOS or NICE clinical practice guideline specific to sesamoid disorders; recommendations are extrapolated from foot and ankle society consensus, AO Foundation principles, and sports-medicine bodies. Where guidance genuinely differs, it is on the threshold for surgery and choice of preservation vs excision.

Registry and Evidence Notes

• No national joint registry captures sesamoid procedures (they are non-arthroplasty), so the evidence base is systematic reviews of case series rather than registry survivorship data.
• Best available syntheses: Shimozono 2018 (sesamoidectomy, 196 feet), Robertson 2017 (stress-fracture return to sport), and Artioli 2025 (nonunion algorithm).

High- vs Limited-Resource Practice Variation

• High-resource settings: Early MRI and CT for diagnosis; custom orthoses; access to arthroscopic and sesamoid-preserving fixation/grafting; bone stimulators for delayed union.
• Limited-resource settings: Diagnosis often radiograph-based with contralateral comparison films; conservative management with stiff-soled footwear and felt dancer's pads; open sesamoidectomy is the dominant surgical option where preservation techniques or implants are unavailable.

Universal Consent Points for Sesamoidectomy

1. Hallux valgus (after tibial excision) or varus (after fibular excision)
2. Cock-up toe deformity from inadequate FHB repair
3. Transfer metatarsalgia to the lesser rays
4. Neuroma (medial plantar or dorsomedial cutaneous nerve)
5. Loss of push-off power, career-relevant for sprinters and dancers
6. Possible revision surgery
7. Always document a minimum 3-6 month conservative trial and MRI-confirmed pathology, and discuss preservation alternatives in athletes.

Related pages: Turf Toe is the acute plantar-plate injury that shares this anatomy and mechanism, and the injury in which a proximally migrated sesamoid on the lateral radiograph tells you the complex has ruptured; Plantar Plate Insufficiency for the same structure failing chronically at the lesser toes; Hallux Valgus for the deformity that both causes sesamoid pain through subluxation of the complex and follows tibial sesamoidectomy - Shimozono found the mean angle change non-significant, but the individual deformity is the reason both sesamoids are never excised; Hallux Rigidus for the other cause of a painful stiff first MTP joint that must be excluded before the pain is attributed to a sesamoid; Metatarsalgia and Metatarsal Stress Fractures for the neighbouring forefoot pain generators and the same overload physiology; Freiberg Disease for the osteonecrosis analogue at the lesser metatarsal head; and Stress Fractures Overview for the bone-stress framework this sits inside.

The evidence base for sesamoid disorders is composed almost entirely of small case series and systematic reviews of them; no randomised trials and no registry data exist. Several genuine areas of debate remain.