The shoulder is a ball and socket joint much like the hip. However, the shoulder has less socket “coverage,” which allows for it to have a significantly larger range of motion than any other joint in the body. The trade off for increased range, however, is often times increased potential for injury and subsequent shoulder pain and discomfort.
The benefit of having a large arc of motion is that it allows you to easily perform a variety of activities such as combing your hair, throwing a baseball and rock climbing. However, the downside of having so much range is that, inherently, the shoulder is more susceptible to injury than if it were less ‘mobile.’ Another way of thinking of this is that, every joint in the body exists somewhere on the spectrum between ‘very stable but less mobile’ and ‘mobile, with less inherent stability.’ The shoulder, lies quite far towards the latter which is partially why it’s more common to dislocate a shoulder as opposed to a hip (which is quite stable and, inherently, has less range of motion than the shoulder.) Often times, a targeted strengthening and stability program geared towards your specific goals will be major component of shoulder rehabilitation. However, sometimes, shoulder pain can be influenced by adjacent neighbors such as the cervical spine or the thoracic spine and will require a significantly different approach.
The term ‘the shoulder’ refers to the glenohumeral joint, or in other words, the joint wherein the humerus and the glenoid (part of the scapula) come together. Around the edge of the glenoid fossa exists a fibrocartilaginous rim named the labrum. The labrum helps improve the stability of the gleno-humeral joint by improving the relative depth of the socket in relation to the humeral head. Not seen in the pictures above, there is a thin joint capsule that encompasses the glenoid and the humeral head that helps to protect and provide nutrition to the joint.
Surrounding the joint, the rotator cuff is a series of 4 muscles (3 in the back, 1 (not pictured) in the front.) As assumed from their name, these muscles help rotate the arm inward and outward. However, most importantly, they help improve the stability of the joint by controlling the humeral head within the joint space and compressing it to the glenoid. If you think of the labrum as a “passive” (meaning you can’t control it) stabilizer of the joint, the rotator cuff is the “active” (meaning you can control it) stabilizer of the shoulder. Superficial to the rotator cuff you have the prime movers of the shoulder such as your deltoids, pectoralis major, and your latissimus dorsi.
All of these structures (along with many that were not mentioned,) act in-concert with one another to move the shoulder throughout our daily activities. Traumatic injuries, loads that surpass our physiological capacity, low-stress movements that are repeated chronically, as well as significant muscle imbalances can all contribute to pain and injury. That’s why there is never a one size fits all approach to treating shoulder pain. Only a thorough evaluation alongside a personalized treatment plan can optimize results for you and your goals.
So What is Causing My Pain?
While pain can come from a number of structures both in and around the shoulder (such as the neck,) the more common culprits of shoulder pain include the rotator cuff, the labrum inside the joint, the long-head biceps tendon, or some combination of these. Rarely do we see shoulder pain coming from the larger muscles such as the pectoralis, the latissimus, or the deltoids. So what does this mean? If you’re having some low level pain in your shoulder, it may be worth gently focusing on rotator cuff strengthening, working on shoulder stability exercises, and loading the long-head biceps tendon to see if that improves your symptoms. If it doesn’t improve, see your local phyiscal therapist for a thorough evaluation. If you’re having sharp, radiating, or persistent pain, see a physical therapist as soon as you can to get some clarity on what is causing your pain.