Common cause of ‘metatarsalgia’. Characterised by painful instability of 2nd metatarsophalangeal joint – thought to be due to pathology of the plantar plate (degeneration or rupture)
Appears to result from a weakening of periarticular ligaments – especially the plantar plate; long second metatarsal has been suggested as a factor; higher heels shoes may increase risk due to dorsiflexed position of metatarsal; HAV may also increase risk; excessive pronation of rearfoot increases forefoot hypermobility; levels of physical activity may also be a factor (especially recent changes);
3 overlapping stages:
1) Stage of simple instability – usually painful on dorsum of 2nd MPJ and/or plantar. Palpation of distal plantar metatarsal head when toe is dorsiflexed is often very painful. Dorsiflexion of toe is often painful. Attempts to vertically displace proximal phalanx on metatarsal head pain and instability. May be more painful during the propulsive phase of gait. Other joint and x-ray findings are normal at this stage. May demonstrate excessive weightbearing under second metatarsal head. X-rays usually normal. This stage is often just referred to as ‘capsulitis’ and this may be a distinct condition. Flexor and extensor tendon/muscle function are usually within normal limits. Dorsal oedema may obliterate normal contour of extensor tendons.
2) Stage of reversible subluxation – 2nd MPJ starts to sublux inflammatory micro traumatic synovial reaction. Plantar oedema can be prominent. Dorsal instability is present, but may not be as painful as first stage. Joint may be fixed. Callus may be present plantar to second metatarsal head. Joint space narrowing on x-ray. Inflammation (maybe a bursitis) may impinge nerve to give neuroma like symptoms. Loss of toe purchase on weightbearing may be present – may also begin to develop medial or lateral deviation at this stage.
3) Stage of definitive subluxation – fixed subluxation/partial dislocation of 2nd MPJ – can be palpated and toe is clawed dorsal and distal lesions. Considered to be due to a rupture of the plantar plate. Gait may be antalgic.
Vertical stress test :
Metatarsal head is stabilised and a vertical displacement force is applied to the proximal phalanx to move it dorsally on the metatarsal head. Pain indicates a positive test. Scale has four levels – 0 = no instability; 1 = mild instability; 2= moderate instability; 3 = dislocatability.
MRI may demonstrate degeneration or rupture of the plantar plate
DDx – neuroma (swelling from capsulitis may cause neuroma)
During stage (1) & (2) foot orthoses with metatarsal pad and cavity for off loading the metatarsal head (accommodation in cavity may give symptomatic relief, but condition may still progress); mobilisation and stretching exercises; NSAID’s; strapping and/or splinting to plantarflex digit; may need steroid injection if synovitis is prominent; stiff soled or rocker shoes
Stage (3) reduction of painful lesions; accommodative padding; cast or footwear immobilisation; surgery (release contracted structures, restoration of plantar plate, decompression of MPJ and realignment of digit) .
Lessor Metatarsophalangeal Joint Synovitis