The function of the anconeus muscle.

The purpose of the present study is to determine whether the anconeus muscle contracts during abduction of the ulna. Abduction of the ulna occurs when pronation takes place around an axis passing through the head of the radius and the second digit. This is in contrast to pronation around an axis passing through the fifth digit, in which the ulna remains relatively stationary. Electromyograms of the anconeus were obtained from five subjects with the elbow supported in 90 degrees of flexion, in full extension, at rest, during supination-pronation around an axis passing through the fifth digit, and during motion around an axis through the second digit. Pronation of the forearm around the axis through the second digit resulted in the greatest amplitude of individual motor unit action potentials and the highest recruitment of additional action potentials. These findings provide evidence substantiating the function of the anconeus muscle as an abductor of the ulna.