Sesamoiditis

Sesamoiditis begins at the first metatarsal head, not the arch.

The sesamoid bones — two small bones embedded in the flexor hallucis brevis tendon beneath the first metatarsal head — absorb enormous pressure during propulsion. When repetitive loading exceeds the tissue's capacity, the tibial or fibular sesamoid becomes inflamed. Without precise offloading at the exact site of pressure, the condition cannot resolve.

Three precise interventions.
One targeted solution.

The P14 doesn't simply cushion the forefoot — it eliminates sesamoid loading at both the frame and extension level while maintaining full forefoot-to-rearfoot balance.

It's not cushioning. It's selective pressure elimination.

A standard cushioned insole distributes pressure evenly — reducing peak forces across the whole forefoot but never fully offloading the sesamoids. The P14 removes the surface the sesamoids press against, creating a true pressure void at the first metatarsal head.

• Frame cutout eliminates rigid contact — removing the polypropylene structure beneath the first ray prevents the frame from acting as a platform that amplifies ground reaction force at the sesamoid site.
• Aperture creates a pressure void — the donut-shaped cutout in the Myolite extension means the sesamoid bones have no surface to press against — offloading them throughout the entire forefoot phase of gait.
• Surrounding support maintains function — the donut design preserves full support around the sesamoid void, maintaining first metatarsal stability and preventing the foot from collapsing into the aperture.
• Congruent fit ensures aperture accuracy — the device is built from the patient's positive model, so the sesamoid aperture lands precisely under the first metatarsal head regardless of foot shape.

How you hold the foot is what we build.

Root is not just the orthotic — it's the clinician's positioning, captured and preserved in the device. For sesamoiditis, precise forefoot-to-rearfoot positioning is critical: the aperture must land under the sesamoids, not adjacent to them.

After every scan, we need to know:

• Was the subtalar joint held in neutral?
• Was the midtarsal joint maximally pronated — loading the 5th metatarsal head?
• Was the midtarsal joint maximally supinated — loading the 1st metatarsal head?
• Was the forefoot brought perpendicular to the rearfoot?
• Was a forefoot-to-rearfoot balance bisection achieved at 90° relative to the Achilles tendon vector?

CAD/CAM fabrication

• Scan or cast captured — clinician captures foot morphology via FootID Pro, holding the subtalar joint in the chosen clinical position.
• Shape modification applied — forefoot balanced to rearfoot, fat pad expanded, arch adjusted using Root's design process.
• Technical staff review — every device reviewed against Traditional Root, Modern Root, Blake Inverted, or Accommodative principles.
• Fabricated to the shape — the frame is vacuum formed over the positive model. The first-ray cutout, sesamoid aperture, Spenco cover, suede bottom, and Myolite extension are then applied.

How your foot shape becomes a precision frame.

The journey from clinical capture to finished P14 frame is where Root's expertise lives. Every step preserves the shape and position the clinician chose — ensuring the sesamoid aperture and first-ray cutout land exactly where the patient's anatomy requires.

• Foot impression captured — the clinician captures the foot using their preferred method. The fashion in which the foot is held directly affects the outcome of the Root Shape congruency against the foot.
• Positive model created — the impression becomes a physical plaster model or a digital CAD/CAM model via FitFoot360. Digital models are stored indefinitely.
• Root technicians modify the shape — using FitFoot360, technicians apply the Modern Root shape process. First-ray cutout location and sesamoid aperture placement are confirmed against the clinical prescription.
• Orthotic frame fabricated — the frame is vacuum formed over the positive model, the first-ray cutout is applied, and the 1.5mm Spenco top cover, .6mm suede bottom, and 3mm Myolite extension with sesamoid aperture are then added.

FitFoot360 Foot Model

• Root digital model stored indefinitely → recalled for future pairs
• Root technicians modify the digital shape in real-time: arch, heel, width, postings
• Vacuum formed over CAD/CAM positive model — replicable, consistent, precise

Designed to eliminate sesamoid pressure at the source.

The P14 is a pathology device designed to treat common inflammation of the sesamoid bones, bipartite sesamoid symptoms, or sesamoid fractures. It effectively offloads both the tibial and fibular sesamoids with a first-ray cutout in the polypropylene frame and a first metatarsal head cutout in the extension.

Precise accommodation for sesamoid pressure is provided by placing a donut-shaped aperture under the first metatarsal head — rather than a nonspecific balance pad. This creates a true pressure void at the exact site of inflammation, not a general reduction in forefoot loading. Designed to fit in most standard shoes with removable sock liners or insoles.

The P14 is constructed with a positive model of the patient's foot and can be modified at the practitioner's discretion.

Sesamoiditis

Sesamoiditis is inflammation of one or both sesamoid bones — the tibial and fibular sesamoids — located within the flexor hallucis brevis tendon beneath the first metatarsal head. These small bones function as pulleys for the flexor tendons and absorb the considerable compressive forces generated at toe-off. Repetitive loading that exceeds the tissue's capacity produces inflammation, pain under the first metatarsal head, and progressive functional impairment.

The sesamoid mechanism

The sesamoids act as a mechanical advantage for the flexor hallucis brevis, increasing the moment arm for great toe plantarflexion. During the toe-off phase, the sesamoids are driven against the first metatarsal head by ground reaction force — a normal biomechanical event. When this compressive loading is excessive or repetitive, the fibrocartilage, periosteum, or the bone itself becomes inflamed or fractured. The tibial sesamoid is more commonly affected due to its medial position and greater loading during normal gait.

Bipartite sesamoid

A bipartite sesamoid is a developmental variant where the sesamoid bone is divided into two segments, joined by fibrous tissue. Present in approximately 10–30% of the population, it is most common in the tibial sesamoid. A bipartite sesamoid can be difficult to distinguish from an acute fracture on X-ray — bilateral imaging assists differentiation. Bipartite sesamoids are inherently more susceptible to inflammation at the fibrous junction under repetitive load.

Contributing Factors

High-impact activity — running, dancing, and jumping sports significantly increase the repetitive compressive load through the first metatarsal head, accelerating sesamoid wear and inflammation.

Plantarflexed first ray — a plantarflexed first metatarsal increases the compressive force on the sesamoids during normal walking by lowering the first ray and increasing the sesamoid-to-ground contact force.

Hallux valgus — lateral displacement of the hallux changes the mechanical relationship of the sesamoids to the first metatarsal head, increasing abnormal shear forces and predisposing to sesamoiditis.

Pes cavus / high arch — a rigid, high-arched foot concentrates loading under the first and fifth metatarsal heads, increasing compressive forces at the sesamoids with each step.

Diagnosis

Diagnosis is clinical: point tenderness directly under the first metatarsal head at the sesamoid site, pain on passive dorsiflexion of the hallux (which compresses the sesamoids), and pain with toe-off. X-ray differentiates fracture from bipartite variant; MRI or bone scan can confirm sesamoid stress reaction or avascular necrosis in complex presentations.

Treatment Pathway

First-line management includes sesamoid offloading via custom orthotics, activity modification, NSAIDs, and occasionally padding or taping. Custom orthotics are the most clinically reliable offloading method — provided the aperture is placed precisely, which requires fabrication from the patient's positive foot model. Generic pads with a cutout are rarely accurate enough to achieve true sesamoid unloading.

The P14 is indicated for tibial or fibular sesamoiditis, bipartite sesamoid, and sesamoid fracture. The aperture design provides targeted offloading that flat cushioning cannot replicate.