Metatarsalgia

Pain in the plantar forefoot under the metatarsal heads, a symptom with many causes, most of them mechanical overload of the metatarsophalangeal joints. It affects up to 10% of adults in some series and is more common in women, runners and the elderly.

• Mechanical causes:
  • Footwear: high heels, narrow toe boxes, thin soles, and worn shoes.
  • Foot structure: a long second metatarsal relative to the first (Morton foot), a short or hypermobile first ray, high arched foot (cavus) with plantarflexed metatarsals, flat foot, hallux valgus, hammertoe and claw toe (with distal migration of the fat pad), and tight gastrocnemius or Achilles tendon.
  • Overload: obesity, running and jumping sports, prolonged standing, and forefoot strike gait.
  • Fat pad atrophy (ageing, steroid injection, diabetes, rheumatoid disease).
• Other causes: plantar plate tear or metatarsophalangeal synovitis (a second metatarsophalangeal joint "crossover toe" deformity), Freiberg infraction (osteochondrosis of the second metatarsal head in adolescent girls), stress fracture, sesamoiditis, interdigital neuroma, rheumatoid arthritis, gout, septic arthritis, peripheral neuropathy, plantar wart, and tumour.
• Plantar callus under the heads is a marker of high pressure, and in diabetic or neuropathic feet is a precursor of ulcer.

• Aching, burning or sharp pain under the ball of the foot, worse when standing, walking, running or barefoot on hard floors, and relieved by rest. Patients describe walking on pebbles or a bruise, or feeling a fold in the sock.
• Examination: tenderness under one or more metatarsal heads (commonly the second and third), plantar callus, prominent heads, toe deformities, swelling and redness at the metatarsophalangeal joint, positive drawer test (instability of the joint with dorsal subluxation of the proximal phalanx in plantar plate tear), and reduced ankle dorsiflexion.
• Differential diagnosis: Morton neuroma (interspace pain with a click and toe numbness), plantar plate tear, stress fracture, Freiberg infraction, sesamoiditis (pain under the great toe metatarsal head), rheumatoid arthritis, gout, infection, diabetic neuropathy and ulcer, plantar wart, and referred S1 pain.
• Red flags: warmth, redness and fever (infection or gout), night pain, inability to bear weight (stress fracture), a non-healing ulcer, loss of sensation or pulses, and a history of cancer.
• Complications: chronic pain, gait change, callus and ulcer, metatarsophalangeal subluxation, and secondary hip, knee and back pain.

• Clinical. Examine the foot standing and walking, the footwear, the ankle range, deformities, callus, vascular status and sensation.
• X-ray (weight bearing anteroposterior, oblique and lateral) shows metatarsal length, stress fracture (may be negative for 2 to 4 weeks), Freiberg changes, arthritis and joint subluxation.
• Ultrasound shows synovitis, plantar plate tears, neuromas, bursae and fat pad thickness. MRI is the best test for plantar plate tears, early stress fracture, avascular necrosis, tumour and infection.
• Blood tests (CRP, ESR, urate, rheumatoid factor, anti-CCP antibodies, HbA1c) when inflammatory disease, gout or diabetes is suspected. Aspirate a swollen joint and send for culture and crystals.

• Footwear and offloading (first line, 6 to 12 weeks):
  • Wide, deep toe box, low heel (below 3 cm), and a thick, cushioned, firm sole. A rocker bottom sole reduces forefoot pressure.
  • Metatarsal pads placed just proximal to the painful heads, metatarsal bars, or custom orthoses with a metatarsal dome and cushioned top layer. Silicone gel insoles for fat pad atrophy.
  • Avoid barefoot walking on hard floors, and high impact exercise in the early phase.
  • Weight loss when overweight.
• Analgesia: ice, paracetamol 1 g orally 6 hourly, and ibuprofen 400 mg orally 8 hourly with food (or naproxen 500 mg 12 hourly) for 1 to 2 weeks. Topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily.
• Physiotherapy and podiatry: calf and Achilles stretching, intrinsic foot strengthening, toe flexor strengthening, and paring of plantar callus every 4 to 8 weeks.
• Specific causes:
  • Plantar plate tear and synovitis: taping the toe in plantarflexion or a toe splint for 6 weeks, a stiff soled shoe, and avoidance of corticosteroid injection (it can cause rupture and deformity). Surgery (plantar plate repair, with or without metatarsal shortening) for failure.
  • Stress fracture: protected weight bearing in a rigid soled shoe or pneumatic boot for 4 to 8 weeks, correct vitamin D (cholecalciferol 1000 to 2000 IU daily) and calcium intake, and review of bone health.
  • Freiberg infraction: rest, a rigid soled shoe and a metatarsal pad for 3 to 6 months, with surgical debridement or osteotomy for failure.
  • Sesamoiditis: a cushioned dancer's pad with a cut out under the sesamoid, rigid soled shoes and rest.
  • Gout: colchicine 500 micrograms orally 8 to 12 hourly (maximum 1.5 mg per day in a flare, reduced in renal impairment) or naproxen 500 mg 12 hourly or prednisolone 30 to 40 mg daily for 5 days, then urate lowering therapy (allopurinol 100 mg daily, titrated every 2 to 4 weeks to a serum urate below 360 micromol/L, with colchicine prophylaxis for 3 to 6 months).
  • Rheumatoid arthritis: disease modifying drugs under rheumatology, custom depth shoes and orthoses.
  • Septic arthritis: urgent aspiration, IV antibiotics (flucloxacillin 2 g 6 hourly, adding vancomycin if MRSA is possible), and surgical washout.
• Corticosteroid injection into the metatarsophalangeal joint is occasionally used for synovitis (triamcinolone 10 mg with lidocaine 1% 0.5 mL), with a risk of plantar plate damage and fat pad atrophy, so use sparingly.
• Surgery for failure after 6 months of conservative care and a fixed mechanical cause: distal metatarsal shortening osteotomy (for example of a long second metatarsal), dorsiflexion osteotomy of a plantarflexed head, correction of hammertoe or hallux valgus, gastrocnemius recession for a tight calf, or condylectomy for a prominent plantar condyle. About 75 to 90% of selected patients improve, with 6 to 12 weeks of recovery.
• Special groups:
  • Diabetes and neuropathy: this is a high risk foot. Use therapeutic footwear, podiatry every 4 to 8 weeks, daily foot inspection, and treat any callus with subcallus haemorrhage as a pre-ulcer needing offloading.
  • Peripheral arterial disease: assess perfusion before surgery or debridement.
  • Pregnancy: supportive footwear, metatarsal pads, and paracetamol. Avoid NSAIDs after 20 weeks.
  • Elderly: fat pad atrophy and deformity are the commonest causes, so use cushioned shoes and orthoses.
  • Renal impairment and gastrointestinal disease: avoid oral NSAIDs.
• Follow up: review at 6 to 8 weeks. Refer to podiatry, orthotics or foot and ankle surgery for deformity, persistent pain beyond 3 to 6 months, suspected plantar plate tear or stress fracture, diabetic or neuropathic feet, or inflammatory disease.