(See also Overview of Foot and Ankle Disorders.)
Metatarsophalangeal joint pain is a common cause of metatarsalgia. Metatarsophalangeal joint pain most commonly results from misalignment of the joint surfaces with altered foot biomechanics, causing joint subluxations, flexor plate tears, capsular impingement, and joint cartilage destruction (osteoarthrosis). Misaligned joints may cause synovial impingement, with minimal if any heat and swelling (osteoarthritic synovitis).
The 2nd metatarsophalangeal joint is most commonly affected. Usually, inadequate 1st ray (1st cuneiform and 1st metatarsal) function results from excessive pronation (the foot rolling inward and the hindfoot turning outward or everted), often leading to capsulitis and hammer toe deformities. Overactivity of the anterior shin muscles in patients with pes cavus (high arch) and ankle equinus (shortened Achilles tendon that restricts ankle dorsiflexion) deformities tends to cause dorsal joint subluxations with retracted (clawed) digits and retrograde, increased submetatarsal head pressure and pain.
Metatarsophalangeal joint subluxations also occur as a result of chronic inflammatory arthropathy, particularly rheumatoid arthritis (RA). Metatarsophalangeal joint pain with weight bearing and a sense of stiffness in the morning can be significant early signs of early RA. Inflammatory synovitis and interosseous muscle atrophy in RA lead to subluxations of the lesser metatarsophalangeal joints as well, resulting in hammer toe deformities. Consequently, the metatarsal fat pad, which usually cushions the stress between the metatarsals and interdigital nerves during walking, moves distally under the toes; interdigital neuralgia or Morton neuroma may result. To compensate for the loss of cushioning, adventitial calluses and bursae may develop. Coexisting rheumatoid nodules beneath or near the plantarflexed metatarsal heads may increase pain.
Metatarsophalangeal joint pain may also result from functional hallux limitus, which limits passive and active joint motion at the 1st metatarsophalangeal joint. Patients usually have foot pronation disorders that result in elevation of the 1st ray with lowering of the medial longitudinal arch during weight bearing. As a result of the 1st ray elevation, the proximal phalanx of the great toe cannot freely extend on the 1st metatarsal head; the result is jamming at the dorsal joint leading to osteoarthritic changes and loss of joint motion. Over time, pain may develop. Another cause of 1st metatarsophalangeal joint pain due to limited motion is direct trauma with stenosis of the flexor hallucis brevis, usually occurring within the tarsal tunnel. If pain is chronic, the joint may become less mobile with an arthrosis (hallux rigidus), which can be debilitating.
Symptoms of metatarsophalangeal joint pain include pain on walking. Dorsal and plantar joint tenderness is usually present on palpation and during passive range of motion. Mild swelling with minimal heat occurs in osteoarthritic synovitis. Significant warmth, swelling, or redness suggests inflammatory arthropathies or infection.
Metatarsophalangeal joint pain can usually be differentiated from neuralgia or neuroma of the interdigital nerves by the absence of burning, numbness, tingling, and interspace pain, but these symptoms may result from joint inflammation; if so, palpation can help with differentiation.
Monarticular heat, redness, and swelling indicate infection until proven otherwise, although gout is more likely. When warmth, redness, and swelling involve multiple joints, evaluation for a systemic cause of joint inflammation (eg, gout, RA, psoriatic arthritis, viral-associated arthritis, enteropathic arthritis) with a rheumatic disease assessment (eg, anticyclic citrullinated peptide [anti-CCP] antibody, rheumatoid factor [RF], erythrocyte sedimentation rate) is indicated.
Foot orthoses with metatarsal pads may help redistribute and relieve pressure from the noninflamed joints. With excess subtalar eversion or when the feet are highly arched, an orthotic that corrects these abnormal alignments should be prescribed. Shoes with rocker sole modifications may also help. For functional hallux limitus, orthosis modifications may further help to plantarflex the 1st ray to improve metatarsophalangeal joint motion and reduce pain. If the 1st ray elevation cannot be reduced by these means, an extended 1st ray elevation pad may be helpful. For more severe limitation of 1st metatarsophalangeal motion or pain, the use of rigid orthoses, carbon fiber plates, or external shoe bars or rocker soles may be necessary to reduce motion at the joint.
Surgery may be needed if conservative therapies are ineffective. If inflammation (synovitis) is present, injection of a local corticosteroid/anesthetic mixture may be useful.
Metatarsophalangeal joint pain most often results from misalignment of joint surfaces, causing synovial impingement with only minimal warmth and swelling, but may be the initial manifestation of rheumatoid arthritis.
Patients have dorsal and plantar joint tenderness with usually minimal signs of acute inflammation.
Diagnose metatarsophalangeal joint pain by the absence of burning, numbness, tingling, and interspace pain (suggesting interdigital nerve pain) and by palpation.
Correct foot biomechanics with orthoses.