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The shoulder is one of the most complex juncture sites in the body, connecting the arm to the trunk. Consisting of three major linking sites — the glenohumeral, sternoclavicular, and acromioclavicular joints — the shoulder allows for the arm to move in straight planes as well as circular planes giving the arm a wide range of motion. Ligaments, or strong strips of flexible yet tough fibers such as the coracoacromial ligament, allow the bones of the arm and shoulder to attach together.
On the top front portion of the scapula, also known as the shoulder blade, there is a curved hook-like projection called the coracoid process. This jutting section of the bone provides stability to the shoulder by giving various muscles and ligaments a place to adhere to the shoulder blade while also allowing this triangular bone to move. Also located on the shoulder blade is a ridge-like ledge, an extension of the scapula’s spine, that projects past the edge of the shoulder blade; it is called the acromion. The coracoacromial ligament stretches in an arched fashion across these two outcroppings and supplies the shoulder with additional stability.
This flexible bridge of connective tissue known as the coracoacromial ligament together, along with the bony protrusions it connects, lies just above the top portion of the arm. This creates a protective ceiling just above the humerus or upper arm bone much like a beach umbrella protects a beachgoer from the harmful rays of the sun. Without this shield the humerus would be more apt to sustaining injuries.
As with any muscle, tendon, or ligament in the body, the coracoacromial ligament is subject to physical damage due to overstretching or overexerting the chorded fibers. Overstretching this ligament can cause a series of what are referred to as microtears, minute splits in the integrity of the fibers. When these tear occur, the ligament weakens. If left untreated these small rips can cause pain and shoulder dysfunction.
A sudden, forceful stretch on the coracoacromial ligament can cause this band to pull away from its bony attachments. When this happens it is a condition known as an avulsion. Partial fiber separation can cause inflammation, or swelling, pain and changes in shoulder movement. If the separation is complete, where the coracoacromial ligament totally detaches from whether the coracoid process or the acromion, shoulder dysfunction and pain symptoms can be severe. Depending on the severity of the injury, treatment protocols range from ice or heat modalities and rest to surgery to repair the integrity of the ligament.