Sharp Under-the-Big-Toe Pain When Pushing Off or Jumping: Not Missing ‘Hallux Sesamoiditis’ as Hallux Rigidus, Hallux Valgus, or Plantar Fasciitis — Dr. Moriwaki on Concentrated Load and Chronic Microdamage at the Medial/Lateral Sesamoids Beneath the First MTP Joint, and the Line Between What Peri-Sesamoid Injection of Stem Cell Conditioned Media Can Address (Sub-Joint Bursal and Bone-Tendon Junction Inflammation) and What It Cannot (Bony Deformity and Sesamoid Fragmentation)2026.08.08

“A sharp, throbbing pain on the plantar side of the big toe base when I push off or jump” / “After high heels or long hours on my feet, a stabbing pain lingers under the ball of my big toe and I can’t hold a single-leg tiptoe.” Behind such chronic pain, concentrated load and repetitive microdamage on the medial and lateral sesamoids — two rice-to-bean-sized bones sitting directly beneath the first metatarsophalangeal (MTP) joint — namely hallux sesamoiditis, may be hiding. Many cases are confused with hallux rigidus, hallux valgus, or plantar fasciitis, and slip by for months or years on painkillers and insoles alone. This column organizes, from the supervising physician’s perspective, the anatomy and differential of hallux sesamoiditis, and what peri-sesamoid injection of stem cell conditioned media can and cannot address.

Key Points

・Hallux sesamoiditis is a chronic inflammatory condition driven by concentrated load and repetitive microdamage at the medial/lateral sesamoids beneath the first MTP joint.

・Hallux rigidus causes ‘dorsal’ bony change, hallux valgus a ‘medial’ bony prominence, and plantar fasciitis a ‘heel-side’ first-step pain — location and provocation differ.

・Peri-sesamoid injection of stem cell conditioned media targets the chronic sub-sesamoid bursal inflammation and the flexor hallucis brevis enthesis irritation cycle.

・It cannot achieve bony union of a symptomatic bipartite sesamoid or sesamoid fracture/nonunion, nor anatomical reversal of MTP bony deformity or advanced cartilage loss.

・Treatment is designed together with metatarsal pads / sesamoid cut-out insoles, activity redesign, and, when needed, imaging (MRI, bone scan).

The Anatomy Behind an Overlooked Chronic Pain

Directly beneath the first MTP joint, the medial and lateral heads of the flexor hallucis brevis (FHB) tendon each contain a small, rice-to-bean-sized bone: the medial and lateral sesamoids. These two bones act as ‘pulleys’ that improve the mechanical efficiency of the FHB during push-off, and simultaneously as ‘cushions and support points’ that shield the first metatarsal head from direct load.

The Chronic Inflammatory Cycle Driven by Concentrated Load

During the push-off of gait, jump take-off, or high-heel forefoot loading, compressive and shear forces reportedly reaching 2–3 times body weight concentrate on the plantar side of the first MTP joint. Runners, dancers, basketball players, kendo athletes and other repetitive-lunge sports, and women who wear high heels daily accumulate these loads. The result is a multi-layered inflammatory cycle: intraosseous edema of the sesamoids themselves, cartilage degeneration between the sesamoid and metatarsal head articulating surface, sub-sesamoid bursitis, and chronic microinjury of the FHB bone-tendon junction (enthesis). Hallux sesamoiditis is an umbrella term for this cluster, not a single lesion.

Differentiating from Hallux Rigidus, Hallux Valgus, and Plantar Fasciitis

Patients usually only say ‘my big toe base hurts,’ and at first visit are easily grouped with hallux rigidus, hallux valgus, or plantar fasciitis. However, careful history and palpation of location and provocation usually narrows things down.

Where the Pain Sits and What Provokes It

Hallux rigidus creates dorsal osteophytes and joint-space narrowing at the first MTP; dorsiflexion of the big toe strongly provokes pain. Hallux valgus centers on medial pain from the bony prominence of the first metatarsal head and the overlying bursitis. Plantar fasciitis is the classic ‘heel-side’ first-step pain at the plantar fascia origin — not a forefoot problem. Hallux sesamoiditis, in contrast, is sharply localized to the plantar side of the first MTP, with reproducible tenderness directly over the sesamoids and traction pain during passive dorsiflexion of the big toe (which stretches the FHB). Weight-bearing X-rays check for bipartite sesamoid or fracture lines; when symptoms persist, MRI should evaluate bone marrow edema, surrounding soft-tissue inflammation, and any signs of osteonecrosis.

What Peri-Sesamoid Injection Can and Cannot Address

This condition is a mixture of soft-tissue-driven inflammation (chronic sub-sesamoid bursitis, bone-tendon microinjury) and structural pathology (symptomatic bipartite sesamoid, fracture/nonunion, cartilage degeneration). How far peri-sesamoid injection of stem cell conditioned media can go must be judged on those two axes separately.

Can Address: Correcting the Inflammatory Environment

Stem cell conditioned media contains growth factors such as TGF-β, IGF-1, FGF, and VEGF along with anti-inflammatory cytokines; it is a biological product expected to modulate chronic inflammatory cycles and act on the peri-entheseal cellular environment. In hallux sesamoiditis, correcting the intra- and peri-articular inflammatory environment — sub-sesamoid bursitis and chronic FHB enthesis irritation — is the layer peri-sesamoid injection can target. Under ultrasound guidance, the sub-joint space between the sesamoid and first metatarsal head and the peri-FHB-enthesis are the targets. See also details on peri-joint stem cell conditioned media injection.

Cannot Address: Bony Union or Anatomical Correction

On the other hand, for symptomatic bipartite sesamoid, obvious sesamoid fracture or nonunion, advanced sesamoid osteonecrosis (Renander’s disease), and marked MTP cartilage loss / osteophytes, stem cell conditioned media is not a treatment that anatomically restores bony union, bone shape, or cartilage defects. Not blurring this line and avoiding phrases like ‘guaranteed result’ or ‘will surely cure’ is the honest stance our clinic maintains when considering this therapy. For general joint disease information, see also the Japanese Orthopaedic Association.

Treatment Design — Running It Alongside Offloading, Insoles, and Activity Redesign

Peri-sesamoid injection is not a stand-alone therapy — it becomes meaningful only when combined with metatarsal pads and sesamoid cut-out insoles that offload directly beneath the sesamoids, a temporary reduction in high heels and forefoot loading, and, for runners and dancers, redesign of distance, pace, and practice content. Efficacy is judged objectively at 6–12 weeks after injection through weight-bearing pain VAS, presence of reproducible pain on dorsiflexion, and tolerance of daily tasks (gait, stairs, tiptoe). When response is poor, it is important to reconsider whether structural pathology (symptomatic bipartite sesamoid, fracture, osteonecrosis) is the main driver and to shift toward additional orthopaedic evaluation (MRI, bone scan) or consultation on surgical options. Response varies by individual; results cannot be guaranteed.

Frequently Asked Questions

Q. Can hallux sesamoiditis be diagnosed with X-ray alone?

Plain X-ray shows bipartite sesamoid (a normal congenital variant of a bone divided into two) and obvious fracture lines or sclerosis, but not intraosseous edema, sub-sesamoid bursitis, or early osteonecrosis. When chronic pain persists, MRI for marrow edema, and bone scintigraphy for metabolic activity when needed, are recommended.

Q. Does one peri-sesamoid injection of stem cell conditioned media resolve it?

In a condition driven by chronic inflammation and repetitive microdamage, complete resolution after a single injection is uncommon. It is a therapy that gradually reshapes the inflammatory environment over weeks to months, planned as multiple sessions combined with offloading and insoles. Response varies individually; no guarantee of outcome can be made.

Q. If diagnosed with bipartite sesamoid, is injection still an option?

When a bipartite sesamoid becomes symptomatic with chronic pain, stem cell conditioned media does not fuse the two bony fragments, but it may help by acting on the surrounding chronic inflammatory cycle. If the main driver is clear fracture, nonunion, or osteonecrosis, orthopaedic evaluation for conservative or surgical treatment takes priority.

Q. When can I return to heels or running after treatment?

For several days after injection, avoid strong forefoot loading, prolonged high-heel wear, all-out sprints, and lunging motions. Then, while preventing flare, offload directly beneath the sesamoids using sesamoid cut-out insoles or metatarsal pads and return to activity in stages. Rather than ‘the pain is gone, so back to normal,’ use this period to redesign the load pattern itself.

Q. Who is not a good candidate?

Active infection in the foot, poorly controlled diabetes / peripheral circulation disorders / systemic disease, cases judged to be primarily driven by clear sesamoid fracture / nonunion / advanced osteonecrosis, and situations where bleeding risk on anticoagulants is hard to manage — in these settings peri-sesamoid injection of stem cell conditioned media may not be the first choice. We assess individually at consultation.

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Supervising Physician: Shin Moriwaki, MD

Member, Japan Society of Aesthetic Surgery (JSAS) / Member, American Academy of Aesthetic Medicine

ECFMG Certificate holder

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📍AVAN TOKYO Ginza Regenerative Medicine

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