Lesser MTP Joint Arthritis

Lesser metatarsophalangeal (MTP) joint arthritis is degenerative disease of the second to fifth MTP joints. The second MTP is the joint most commonly affected, because of its mechanical disadvantage. The disease progresses from synovitis and cartilage wear to subchondral sclerosis and osteophyte formation, and eventually to joint destruction with fixed deformity.

Natural history. It is a common source of forefoot pain but is often underdiagnosed in its early stages. The course is progressive: early synovitis evolves to cartilage loss and joint-space narrowing, and eventually to fixed deformity with secondary deformities in the adjacent toes.

Who. Typically presents at 40-60 years, with a female predominance of 3:1. Prolonged standing, athletics and dance load the forefoot, as do high heels, a narrow toe box and obesity.

Causes and associations. In chronic cases the arthritis is never isolated. Look for the associated deformity, because failure to address it leads to recurrence:

• Hallux valgus (a 15-20% association) and other first-ray insufficiency, which transfers load to the lesser rays
• Inflammatory arthritis: rheumatoid, psoriatic, gout
• Plantar plate insufficiency and tears, which may be a precursor or a consequence
• Toe deformities: hammertoe, claw toe, and crossover toe with its progressive instability
• Trauma: fracture, dislocation, turf toe
• Rigid flatfoot, through abnormal biomechanics
• Sesamoid dysfunction, with loss of first MTP load bearing
• Iatrogenic: overcorrection of hallux valgus, and transfer metatarsalgia after first-ray surgery

The joint. Each lesser MTP joint is a condyloid synovial joint between the convex metatarsal head and the concave base of the proximal phalanx. Its stabilisers:

• Plantar plate, providing static stability and resisting hyperextension
• Collateral ligaments, medial and lateral
• Intrinsic muscles, the interossei and lumbricals, which control toe position
• Extensor and flexor tendons, the dynamic stabilisers

The plantar plate. A rectangular fibrocartilaginous structure that originates from the plantar metatarsal neck and inserts on the base of the proximal phalanx, blending with the joint capsule and collateral ligaments. Attenuation or rupture, typically on its dorsal-lateral aspect, leads to MTP instability, dorsal subluxation and accelerated arthritis. That is why an isolated arthrodesis that does not address the plantar plate can fail.

Load sharing. Normally the first MTP carries 50% of forefoot load, the second 30% and the third to fifth 10% each, with peak pressure in terminal stance. With hallux valgus the second MTP's share increases to 60% or more.

Why the second MTP. It experiences the highest ground reaction forces in gait, and the second metatarsal is typically the longest. When the first ray is insufficient, from hallux valgus, hypermobility or iatrogenic shortening from an overzealous Weil osteotomy on the first metatarsal, load transfers laterally and the second MTP absorbs it. Overload then feeds a vicious cycle of synovitis, plantar plate damage, instability and accelerated arthritis.

The cascade. The sequence typically runs:

1. Initiating event: overload (hallux valgus, long metatarsal), trauma or inflammatory disease
2. Synovitis: inflammation, effusion, capsular distension
3. Plantar plate attenuation, as chronic synovitis weakens the plantar restraint
4. Instability and subluxation, with dorsal migration of the proximal phalanx
5. Cartilage wear from abnormal load
6. Subchondral change: sclerosis, cysts, osteophytes
7. Fixed deformity: contracture of the dorsal structures, crossover toe
8. Secondary deformity: transfer metatarsalgia, adjacent toe deformities

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Deformity progression. Clinically, the deformity is staged:

• Stage 1: synovitis, mild dorsal subluxation
• Stage 2: plantar plate attenuation, reducible deformity
• Stage 3: cartilage loss, fixed deformity
• Stage 4: bone-on-bone, crossover toe, transfer lesions

Two systems describe the joint itself. The clinical severity grade is the one that directs treatment, and it matters more for treatment decisions than the radiographic stage alone. Grades I-II typically respond to conservative measures for 6-12 months; failure of conservative treatment in Grade II, or presentation with Grade III-IV disease, prompts surgery, with the procedure matched to severity and to the patient's demands.

Plantar plate grading. The plantar plate has its own anatomical grading (Nery), which the plantar plate literature uses to match the procedure to the tear.

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History. The pain lies over the dorsal MTP joint and the plantar metatarsal head, and its onset is insidious or, after trauma, acute. Push-off, barefoot walking and stairs aggravate it; rest and supportive shoes relieve it. Establish the functional impact, particularly on athletic activity, what has already been tried (orthotics, injections, footwear changes), any associated hallux valgus or toe deformity, and screen for the systemic symptoms of inflammatory arthritis.

Examination.

• Inspection: swelling, erythema, hammertoe or crossover deformity
• Palpation: joint-line tenderness, osteophytes, a prominent metatarsal head
• Active and passive dorsiflexion and plantarflexion, compared with the other side
• Stability: the drawer test for plantar plate integrity
• Alignment: coronal deviation and rotation
• Transfer lesions: plantar calluses under the adjacent metatarsals
• Shoe wear, which shows how the load is distributed

Reading the drawer. Judge the translation against a normal toe. Early tears are reducible; late ones become fixed.

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Arthritis or plantar plate tear? An isolated plantar plate tear presents acutely, with a positive drawer test and instability, and its radiographs may initially be normal. Lesser MTP arthritis typically has an insidious onset, joint-line tenderness, reduced movement and radiographic change. Chronic plantar plate tears lead to arthritis, however, so the two sit on a spectrum, and MRI separates the acute tear that is amenable to repair from the chronic tear with arthritis that needs arthrodesis or arthroplasty.

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Radiographs. Weight-bearing AP, lateral and oblique views of the foot come first. Non-weight-bearing films underestimate joint-space narrowing and subluxation, so standing views are mandatory: they show true alignment and joint space under physiological load, and they are the standard of care for forefoot pathology. Look for:

• Joint-space narrowing
• Subchondral sclerosis
• Osteophytes
• Dorsal subluxation of the proximal phalanx
• The metatarsal length relationships
• Transfer lesions, seen as narrowing of the adjacent joints

MRI. The gold standard for soft tissue and cartilage. Use it when a plantar plate tear is suspected, for early arthritis with normal radiographs, or for pre-operative planning. It shows:

• Plantar plate tear, high- or low-grade
• The extent of cartilage defects
• Bone marrow oedema, which suggests acute overload
• Synovitis, as T2 hyperintensity in the joint
• Collateral ligament integrity

Its accuracy for plantar plate tear rests on one cited series (Yamada, 45 joints against a surgical reference standard): pericapsular fibrosis was 91% sensitive, with a specificity resting on only 11 tear-free joints.

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Ultrasound. A dynamic assessment of the plantar plate, and less expensive than MRI. It shows plate thickness (normal 3-4mm), tears and hyperaemia, but it is operator-dependent and less accurate than MRI for grading tear severity.

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Blood tests. Isolated degenerative arthritis does not need blood work. If an inflammatory arthropathy is suspected:

• Rheumatoid factor and anti-CCP for rheumatoid arthritis
• Uric acid for gout
• ESR and CRP as inflammatory markers
• HLA-B27 for the spondyloarthropathies

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Choosing the operation. The choice depends on disease severity, the patient's age and activity level, bone quality and the associated deformities.

Arthrodesis or arthroplasty. Arthrodesis provides pain relief and stability but risks transfer metatarsalgia; arthroplasty preserves motion but has a higher recurrence. Combine either with a metatarsal osteotomy for load balancing. For the elderly, low-demand patient with poor bone, arthroplasty, resection or implant, preserves length at the price of accepting instability.

Transfer metatarsalgia, the most common complication. It occurs when an arthrodesis or shortening osteotomy alters the metatarsal parabola and shifts load to the adjacent metatarsals. Prevention is the key: assess the metatarsal length relationships on the pre-operative radiographs, perform balancing osteotomies when needed, and avoid over-shortening. Once established it is treated with offloading orthotics first, and persistent symptoms may need revision with a metatarsal osteotomy.

Arthrodesis is protected longer. The weight-bearing protocol after lesser MTP arthrodesis is more conservative than after forefoot osteotomies, and premature weight-bearing risks nonunion. Heel weight-bearing only for 2-4 weeks, flat-foot in the post-op shoe for 4-6 weeks, then supportive shoes at 6-8 weeks. The Weil osteotomy allows earlier weight-bearing, but stiffness is more common after it, so emphasise early range-of-motion exercises.

Conservative care. The textbook reference says conservative care "resolves the majority of early lesser MTP pain", which is the strongest supportable claim: no source cited on this page quantifies the success rate or the proportion who progress to surgery. Early presentation, compliance with orthotics and avoiding aggravating footwear predict success.

Predictors of a poor outcome.

• Failure to address the biomechanics: hallux valgus, metatarsal length discrepancy
• Smoking, which increases the nonunion risk
• Diabetes or peripheral vascular disease, with healing complications
• Inflammatory arthropathy, with higher recurrence
• The wrong procedure for the severity: cheilectomy fails in Grade IV disease
• Malalignment: malunion or uncorrected deformity

Why define it. Restoring or balancing the metatarsal parabola, and shortening a "long" metatarsal, is the most-repeated surgical principle in this condition, so the normal parabola and how it is measured need defining.

The parabola. The smooth, harmonious curve joining the tips of the metatarsal heads on a weight-bearing AP radiograph. Lengths decrease in an even progression: the second is usually the longest, or the first and second are roughly equal, and each of the third, fourth and fifth is a few millimetres shorter than the one medial to it. A break in the curve, most often a relatively long second metatarsal or a short first ray, concentrates load on the prominent head, and is the mechanical driver of overload referred to throughout this page.

The metatarsal formula. The index describes the first-to-second relationship:

• Index plus: first metatarsal longer than the second
• Index plus-minus: first and second equal
• Index minus: first shorter than the second

An index-minus foot, with a short first ray from hallux valgus or an over-shortened first metatarsal, transfers load to the second MTP: this is the first-ray insufficiency mechanism.

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Maestro's criteria. A reproducible planning target. The lesser metatarsal heads should lie on a harmonious curve with the second at the apex, the fourth metatarsal head is referenced to the line joining the centres of the lateral sesamoid and the fourth metatarsal head, and there is a regular geometric decrement from the second through the fifth. Restoring this geometry, rather than simply shortening the sore ray, is what prevents transfer metatarsalgia.

In practice. Before any lesser MTP arthrodesis or Weil osteotomy, template the parabola on the weight-bearing AP. Shorten only enough to sit the operated head on the curve, and if the first ray is short, consider lengthening or plantarflexing it rather than shortening the lesser rays alone.

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Floating toe and reduced MTP motion are the signature complications of the Weil osteotomy. Both follow directly from what the osteotomy does to the joint, so they can largely be designed out.

Why the toe floats. The Weil cut is made almost parallel to the sole, so as the metatarsal head is translated proximally it also drops (plantar-translates). That lowers the MTP joint axis, and the intrinsic muscles (interossei and lumbricals), whose tendons now pass dorsal to the new axis, lose their plantarflexion moment and can even act as extensors of the proximal phalanx. The toe then sits dorsiflexed and no longer purchases the ground, and MTP stiffness from the intra-articular osteotomy and capsular scarring compounds it.

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Reducing the risk.

• Do not over-shorten or over-plantar-translate the head; take only what the parabola needs
• Elevate the head by removing a thin dorsal wedge (the "double" or triple Weil, a dorsal closing-wedge modification), so the head is shortened without being dropped and the joint axis stays up
• Balance the intrinsics: release a tight dorsal capsule and EDL, and add a flexor-to-extensor (Girdlestone-Taylor) transfer or a plantar plate repair where there is instability
• Start early active and passive MTP range of motion to limit stiffness

Why it matters. The Weil osteotomy is used both to offload an arthritic joint and to balance the parabola, so understanding the floating-toe mechanism is what lets you shorten safely and counsel the patient on the characteristic trade-off.

Lesser MTP arthritis and the closely related plantar plate instability spectrum are common globally, with female predominance, and the second ray most frequently involved. There is no single dedicated national guideline; practice is governed by foot-and-ankle society consensus, surgical textbooks (Mann's, Coughlin), and procedure-level registry and cohort data.

Arthrodesis or motion-sparing surgery. No randomised trial compares lesser MTP arthrodesis with Weil osteotomy or implant arthroplasty. Arthrodesis is conventionally held to give the most reliable pain relief, at the cost of motion; the threshold at which to abandon joint preservation in degenerative, rather than purely unstable, disease remains opinion-based.

Durability of plantar plate repair. Grade-matched repair improves alignment and pain, but advanced (grade IV) tears retain residual instability and poorer scores. Whether direct repair alters the natural progression to arthritis, or simply delays it, is unproven.

The fixation construct. Plating is biomechanically more stable than K-wire fixation, but no series cited here reports a lesser MTP fusion rate for either construct, there is no high-level head-to-head trial, and hardware prominence drives a meaningful reoperation rate. The ideal construct (plate, screw, intramedullary device) is unsettled.

Defining and grading the disease. There is no universally accepted radiographic classification for lesser MTP arthritis itself; grading borrows from plantar plate (Nery) and clinical severity systems. That limits comparison between studies and complicates evidence synthesis.