The glenohumeral joint (shoulder joint) like the hip is a ball and socket joint that provides the most degrees of freedom allowing for ROM in 3 planes. These passive structures, however, provide very limited stability to the joint. The overwhelming contribution to stability comes from active stabilizers, AKA muscle, the rotator cuff. With an anatomical structure that promotes increased mobility, we inherently sacrifice the overall stability of the joint. The glenohumeral joint does have passive stabilizers such as the glenoid labrum which lines the cup aspect of the scapula, the glenoid fossa, and suctions onto the head of the humerus. It also has a ligamentous complex which is intimate or entwined with the joint capsule which further reinforces the joint preventing excessive humeral head translation.
What is the Rotator Cuff?
The rotator cuff is made up of 4 muscles that originate off the scapula, or shoulder blade, wrapping around inserting on the head of the humerus. Coming from the posterior aspect, or backside, of the scapular, are the supraspinatus, infraspinatus, and teres minor muscles. These muscles are responsible for initiating lifting of the arm as well as external rotation of the shoulder. Off the anterior aspect, or front side, of the scapula, is the subscapularis which is an internal rotator of the shoulder joint. Active contraction from these 4 muscles dynamically stabilizes the shoulder joint when we do functional movements such as lift heavy objects, throw a ball, swing a bat/club/racquet, or support our body weight with our hands fixed to the ground (ie. push up or plank position).
These muscles are oftentimes implicated with acute and chronic shoulder pain, which can be caused by chronic impingement leading to tendon fraying or tearing. Depending on the degree of tearing and functional limitations surgical repair may be necessary. Our body’s natural response is to try and fill the void caused by the tear and do so by laying down adipose or fat tissue. On an MRI you may see grading of the tear, which will be based on the amount of tearing in centimeters as well as the condition of the tissue described by the amount of “fatty infiltrate”. Surgery is often recommended if the tear occurs from acute trauma, is greater than 3cm, and the surrounding tissue is of good quality. The most commonly torn rotator cuff muscle is the supraspinatus due to its most superior orientation in the subacromial space.
The simplified explanation of the surgical procedure is essentially stitching of the tendon back to its original attachment site on the humeral head. Also due to chronic mechanical stress, osteophyte formation or bone spurring can occur on the undersurface of the clavicle, which will rub on the supraspinatus tendon every time the arm is lifted overhead.
Post-operative rehab for a rotator cuff repair typically follows a time and criterion-based progression allowing for progressive increases in shoulder ROM and stressing of the rotator cuff. ROM is limited and gradually progressed to allow the surgically repaired tendon to heal. Our bodies positively respond to stress when it is applied correctly and this principle is applied to surgically repaired tissue. Once appropriate we can begin to strengthen the rotator cuff progressing from isometrics to concentric to eccentric varying positions to relate to function and eventually doing so in dynamic patterns related to sport. Often overlooked is the importance of strengthening the middle and lower trapezius muscles. These two muscles, in conjunction with the serratus anterior, work in unison to stabilize the scapula, providing a functional base for our rotator cuff to efficiently work off of.
Contact us today to start your rehab on your shoulder. You won’t be referring to it as your bad wing anymore!