The shoulder is a group of joints, tendons, and muscles that make the arm the most flexible joint in the human body. The shoulder is the largest joint, where the humerus (or upper arm bone) connects to the scapula (shoulder blade) and the clavicle (collarbone). It’s a kind of synovial joint called a ball and socket joint, and it works using the same principle as mechanical ball and socket joints (below).
The humerus ends in a ball that fits snugly into a cavity in the shoulder blade. A group of muscles, together called the Rotator Cuff, extend over the joint and attach the humerus to the shoulder blade. Inside the joint itself, the humerus is insulated by a smooth surface of articular cartilage and the cavity is padded with soft tissue. The two surfaces are protected and lubricated by the synovial lining. These layers of padding prevent contact between the humerus and shoulder bones and therefore enable a very wide range of motion.
Due to the regular stress the joint undergoes during exercise and daily life, shoulder injuries aren’t uncommon; you may know someone who has had a dislocated shoulder. These injuries are usually treated with physical therapy after a process called reduction. Reduction is performed as a doctor will carefully put the bone back into its place while the patient is under local or general anesthesia.
What Are My Options?
While some injuries can be healed over time with physical therapy and pain management, others may require surgery. A dislocation can lead to joint instability, making subsequent dislocations much more likely. Eventually, a dislocation can cause or exacerbate other problems. Rotator Cuff tears are another common injury. A tear can be partial or full-thickness, depending on the extent of damage. Tears cause inflammation, pain, limit movement and aggravate existing conditions. The majority of even full-thickness tears, however, respond to non-surgical treatments in the majority of cases. Unless the injury or condition poses an immediate threat to the arm’s function, doctors will recommend that surgery be treated as a a last resort, after other treatments prove ineffective. Rotator Cuff surgery may be indicated when there is a tear of three centimeters or greater, when there is significant loss of function, symptoms persist for more than six months, or when the damage is caused by a recent acute injury. Surgery most often involves re-attaching the rotator cuff to the humerus. Surgeons may also need to connect the muscles back to each other if the tear is complete. A partial-thickness injury may only require shaving down bony protuberances that come from the tear.
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