Levator Scapulae Action during Shoulder Movement: A Possible Mechanism for Shoulder Pain of Cervical Origin.

The phenomenon of shoulder pain of cervical origin being reproduced on shoulder movement is clinically recognized. The action of the shoulder girdle muscles is a hypothetical cause of the cervical stress. This study examined the mode and degree of Levator Scapulae activity during shoulder activity. Electromyography and x-rays were used to measure levator scapulae activity and length. The results of the study show that levator scapulae contracts concentrically during the first 90 degrees of shoulder abduction and eccentrically during the second 90 degrees. The action of levator scapulae may be responsible for the application of force on the cervical spine during shoulder abduction. This force might cause cervical joint tissue distortion and pain if a pathological state was present.