In dogs, the articular capsule of the shoulder joint forms a loose sleeve that attaches just peripheral to the glenoid lip proximally. In places the capsule attaches several millimeters distal the articular part of he humeral head, where it blends with the periosteum on the neck of the humerus.
A part of the joint capsule surrounds the tendon of origin of the biceps brachii and extends distally approximately 2 cm in the intertubercular groove. The capsule blends with the transverse humeral retinaculum craniomedially and with the tendon of subscapular muscle medially. Laterally the joint capsule blends with the tendons of supraspinatus and infraspinatus. Elsewhere, especially caudally, the articular capsule is thin and expansive possessing a number of irregular pouches when it is distended. Medially and laterally, the fibrosa of the capsule is irregularly thickened internally to form the medial and lateral glenohumeral ligaments.