Shoulder pain is usually caused by an injury to the rotator cuff tendons. The rotator cuffs are a group of four muscles (Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis) that help stabilize the shoulder joint which is made up of the humeral head and glenoid cavity, or fossa. The humeral head is the ball at the upper part of our upper arm. The glenoid cavity, or fossa, is the part of the shoulder blade where the humeral head sits. It is here that the humeral head moves around the glenoid cavity, or fossa, like a ball-and-socket joint.
As mentioned, the rotator cuff muscles help stabilize the humeral head in the glenoid cavity, or fossa. This allows for the arm to move around with great flexibility and range of motion without falling out of the socket. However, putting too much stress on the rotator cuffs can cause them to be injured. Initially, there may be some tendonitis and bursitis present due to inflammation. This can usually be treated conservatively with rest, ice, NSAIDs, and physical therapy. If the pain persists, then a steroid injection can be performed to calm down the inflammation.
Shoulder Tendinosis or Tendinopathy
However, if the rotator cuffs are continually injured, then this can result in wearing out, or degeneration, of these tendons. This can be described as tearing, either partial- or full-thickness, and is termed tendinosis (or tendinopathy). Since these are now chronic (or long-standing) injuries, there is actually no longer any inflammation present. Thus, the same conservative treatments that were used to treat the acute tendonitis from before will no longer be helpful to reduce pain anymore. In this case, surgery or Regenerative Medicine may be indicated.
Chronic rotator cuff injuries can be diagnosed with MRI and ultrasound. Platelet-Rich Plasma (PRP) and Stem Cell Therapy can help heal damaged and partially torn rotator cuff tendons without needing surgery. However, if there is a full-thickness tear with associated severe lack of function and use of the arm and shoulder (as in the inability to even lift the arm up from the side of the body), then surgery may be required to fix the tear. Full-thickness tears can also occur from a traumatic injury such as a hard fall onto the shoulder or with the arm outstretched, rather than an overuse wear-and-tear type of chronic injury.
In a sense, chronic rotator cuff injuries are like arthritis of the soft tissue structures of the shoulder (rather than bony arthritis which is typical) since they usually develop from overuse and wear-and-tear over extended periods of time such as years or even decades just like arthritis does. Although the bones are not directly affected in this case arthritis in the bones of the shoulder joint can also develop over time due to the instability created by the injured and damaged rotator cuff tendons. Again, this arthritis is typically a secondary development due to underlying rotator cuff problems. Hence why it is important to treat the underlying problem with the rotator cuff tendons in addition to addressing the bony arthritis. In severe cases of shoulder arthritis, a shoulder replacement surgery may be a treatment option.
Frozen shoulder is a condition that develops from disuse of the shoulder, usually as a result of an underlying injury to the rotator cuffs as detailed above. If the pain or the damage to the rotator cuffs is so severe that a person stops using their shoulder and moving their arm, then it can become "frozen" in place. This is a serious condition that is difficult to treat and should be avoided if at all possible. It is important to see your doctor and begin treatment before your flexibility and range of motion begin to decline to ensure you maintain good use and function of your arm and shoulder.
AC Joint Sprain or Separation
AC joint sprains are another common cause of shoulder pain. These are usually traumatic injuries that result from direct contact to the shoulder, such as when a player is tackled to the ground during a football game and lands hard on the shoulder. There are several ligaments that help stabilize this small joint in the shoulder. The AC joint is located on the top of the shoulder where the collar bone, or clavicle, and acromion on the shoulder blade meet. If the trauma is severe enough, then these ligaments can rupture and the AC joint can even become separated to the point of requiring surgery in order to put the bones back into their normal location and fix it. In less severe cases, conservative management can be used to help treat the injury including rest, ice, bracing, NSAIDs, and physical therapy.
The labrum is a ring or band of cartilage that is part of the shoulder joint. The shoulder joint has a ball-and-socket structure to it. The labrum fits around the ball like a tight sleeve where it meets the socket of the joint. This helps to stabilize the joint so it does not dislocate out of place.
Injury to the shoulder joint can result in damage to the labrum. This will result in an unstable joint that can cause pain, especially with movement. The labrum can tear from a traumatic injury or it can wear out over time from overuse and cause degenerative tearing.
A labral tear requires an MRI to diagnose it. Often, a special type of MRI called an arthrogram is even necessary. The arthrogram includes contrast in order to help see deeper into the joint where the labrum is located. Ultrasound is not as useful for diagnosing labral tears due to the depth of the injury.
If conservative treatment fails with physical therapy and NSAIDs, then arthroscopic surgery should be considered. If you are a more active individual, you may also want to consider surgery sooner. In cases where you would like to avoid surgery or surgery has failed then you can try Regenerative Medicine with either Platelet-Rich Plasma (PRP) or Stem Cell Therapy to help heal the damaged labrum.