Our shoulder is not a single joint but multiple joints from different bones around the shoulder. Since the shoulder can only compromise stability or mobility, it is the most mobile yet very unstable complex in the human body. The primary function of the shoulder is to articulate the upper arm and provide stiffness to the whole arm in allowing responses to perturbation. The glenohumeral joint is one of the many joints in the shoulder. It is composed of the humerus and socket of the scapula, referred to as the glenoid. Today, we will be focusing on the group of muscles around the GH joint, called the rotator cuff.
The rotator cuff includes four small muscles – supraspinatus, infraspinatus, subscapularis, and teres minor. They are responsible for different actions, but all are critical for joint stability. There is also a subacromial space at the GH joint created by the bones and involves one of the rotator cuffs, which would further provide the shoulder’s stability.
The mechanism of injury for rotator cuff tears can be separated into two categories. As we age, our tissues would degenerate on themselves, and possibly bone spurs would grow. This would result in muscle weakness and imbalance. Additionally, traumatic factors could compress the tissues mechanically and lead to inflammation/ microdamage which causes catastrophic damage. As the subacromial space becomes smaller, the rotator cuff would get squeezed between, especially the supraspinatus. The damage would radiate and causes either partial or full-thickness tear. Full-thickness tear means that the tendon is detached from the bone, and vice versa for partial tear.
Symptoms could include pain during the night, particularly lying on the side, and weakness/ pain when rotating and lifting arms. Nonsurgical treatment could relieve pain and improve function in the shoulder. Physiotherapy treatments could educate patients on how to strengthen their muscles, aiming to improve their range of motion and mobility. Practitioners could suggest surgery to repair the tear when nonsurgical treatment would not ease the pain.