Documenting rotation at the glenohumeral joint. A technical note.

Present methods of documenting internal rotation of the shoulder joint are based on the point reached over the back by the tip of the fully extended thumb. Disease or stiffness of the joints distal to the shoulder gives a false measure of internal rotation. Using the interepicondylar line of the humerus in the coronal plane as the neutral position, internal rotation can be documented accurately as the angle formed by this line with the coronal plane when the shoulder is rotated inwards.