The subsacpularis muscle originates from the underside of the shoulder blade and inserts at the front of the upper arm (humorous).
It medially rotates the arm and also helps to extend the arm. The deltoid muscles elevate the arm further.
The middle glenohumeral ligament stabilizes with the subscapularis.
This test involves holding the hand behind the back (like a police arrest hold except into a mild boundary) with the palm facing away from the body. Push gently on the palm away from the back while a gentle force is applied forward. If the muscle is injured pain will occur. If only mild or no force can be applied the muscle may be torn.
When the hands are interlocked behind the back the supraspinatus is stretched. This is done in many postures such as Plough Pose.
Some subscapularis tears are repaired surgically by direct repair of the tendon which has excellent results. For chronic irreparable ruptures reconstruction tendon transfer is recommended. Tendon transfers from the trapezius, pectoralis major and the pectoralis minor can restore good functional use of the subscapularis.
Loss of subscapularis function usually causes painful dysfunction of the shoulder.
This lying spinal twist can be a create way to stretch the subsacpularis muscle. The muscle gets stretched even more when the arm is raised above the shoulders and extended out correctly.