Normal anatomy of the medial aspect of the canine shoulder. Normal shoulder anatomy medial aspect demonstrating the subscapularis muscle and tendon unit. Subscapularis Supraspinatus Medial Glenohumeral Ligament Shoulder abduction test being performed on a Border Collie with MSS. Biceps Brachii Tendon Joint Capsule Transverse Humeral Ligament Synovium Biceps Brachii Muscle Humerus © Cindy Telley Normal arthroscopic ÿ ndings. A B C a. Articular surface of the glenoid cavity a. Articular surface of glenoid cavity a. Articular surface of glenoid cavity b. MGL b. MGL/Joint capsule b. Medial glenohumeral ligament (MGL) c. Subscapularis tendon d. Articular surface of humeral head Arthroscopic ÿ ndings in a dog's shoulder with MSI. Subscapularis tendon disruption and hypertrophy Compare to A:c above Medial Glenohumeral ligament fraying. Compare to A:b and B:b above Severe synovitis and joint capsule hypertrophy Compare to C:b above Arthroscopic radiofrequency being performed on a dog. 18 Clean Run | January 16