In an experimental study we investigated the EMG response in 10 human subjects after intraarticular stimulation of the shoulder joint capsule following arthroscopic insertion of the stimulating electrode in the anterior glenohumeral ligaments. The muscle response was documented by mono- or bipolar electrodes. Reproducible EMG response patterns were present in superficial as well as in deep muscle layers. The response time ranged from 100 to 516 msec. The earliest muscle response was found in the anterior part of the deltoid muscle and the latest one in the supraspinatus muscle and the lateral part of the deltoid muscle.
Clinical relevance: The results of this study suggest a significant influence of the tension in the joint capsule on the activity of the stabilizing musculature.