Among 703 professional pianists with medical problems in their hands seen by the author between 1981 and 2000, there were 27 patients who had interosseous muscle pain (23 women, 4 men; mean age, 30 yrs). The main symptom was dorsal hand pain during piano performance, especially when
striking the keys with each finger rounded, mainly in the scale technique. Tenderness was noted in the deep part of the dorsal hand in the interosseous muscles, but not along or around the finger extensors. Patients sometimes complained of muscle weakness on abduction of the index, ring, and/or
little fingers when performing octaves or chords on the piano keyboard. Resisted abduction and adduction testing of the fingers reproduced the pain which they experienced during or after performance. Pain occurred in the right hand in 10, left hand in 5, and bilaterally in 12. The pain was
localized in the 4th and 5th interossei in 15 patients, in the 3rd and 4th in 14 patients; in the 2nd and 3rd in 11 patients; and in the 1st and 2nd in 1 patient.