Lumbrical tears in rock climbers.

Performance rock climbing places high demands on the hand and may lead to specific injuries. In a "one-finger-pocket" hold, the interphalangeal joints remain in 20-40 degrees flexion. To increase the maximum force of the holding finger by the quadriga effect, the interphalangeal joints of the adjacent fingers become almost maximally flexed. Holding a "one-finger-pocket" with the ring or small finger leads to a shift of the deep flexor tendons which increases the distance between the two adjacent origins of either the third or the fourth lumbrical. This may cause disruption and tear of that muscle. An organized haematoma in the third lumbrical was visible by ultrasonography in one of the three cases described.