Flexor tendon sheath as a source of pain in lesser metatarsal overload

Lesser metatarsal overload may lead to pathologic conditions ranging from plantar metatarsophalangeal joint pain to dislocation. The flexor tendon sheath lies directly plantar to the joint. The increased pressure associated with lesser metatarsal overload may lead to synovitis and pain of the flexor tendon sheath.

Fifteen consecutive patients with lesser metatarsal overload had visual analog scale scores determined at three metatarsophalangeal joint areas to determine the source of pain. The patients underwent seven maneuvers to determine the pain scale score: single-leg heel raise and palpation of the second and third metatarsophalangeal joints on the plantar proximal, plantar distal, and dorsal aspects. The patients were then injected with 0.5 mL of lidocaine, 2%, into the second and third flexor tendon sheaths, and the maneuvers were repeated.

Before the injection, the second metatarsophalangeal joint had a significantly greater visual analog scale score plantar than dorsal (6.9 and 2.6, P < or = .01). The flexor tendon sheath injection significantly improved all seven pain scale scores.

Patients with lesser metatarsal overload experienced significantly greater visual analog scale pain scores on the plantar than the dorsal aspect of the second metatarsophalangeal joint. The scores significantly improved after diagnostic injection in the flexor tendon sheaths. The flexor tendon sheaths are probably involved in patients with primarily plantar pain.