WHAT CAUSES SHOULDER PAIN?
The shoulder is a very mobile joint. Due to the large range of motion there is little bone stability. Because of this support must come from the connective and soft tissue around the joint. The rotator cuff is a group of four muscles that originate on the shoulder blade and insert into the upper arm and provide stability to the shoulder. They also act as the prime movers for rotation and sideways lifting. Inability to sufficiently stabilise the joint is one of many potential causes of shoulder discomfort. Here are some other possible causes and symptoms that you may be feeling.
- Instability - excessive movement that cannot be adequately controlled by the muscles is a common cause of an unstable shoulder. It can also be caused by sport injury or a motor vehicle accident which could cause a previously stable joint to become dysfunctional, or even come out of joint (subluxation is temporary, a dislocation remains out of socket until it is reduced and requires immediate medical assistance). Symptoms may include, but are not exclusive to, pain or clicking in particular movements, feelings of the joint sliding, weakness in extreme ranges of motion. A shoulder separation refers to a ligamentous injury at the acromioclavicular (AC joint), and often occurs due to a fall on an outstretched hand, or contact injury sports. Typically, a step deformity can be noted at the outer portion of the shoulder, where the collar bone meets the shoulder blade.
- Rotator Cuff Strain, Tendonitis or Tendinosis - the rotator cuff can be stressed due to instability, excessive load or repeated movements of the shoulder, poor posture, or weakening of the tendon due to age or improper nutrition at the tendon sheath. Symptoms generally include achiness in the upper arm, difficulty in sleeping, pain in the mid-range of lifting the arm, and painful weakness when trying to lift or move the arm.
- Rounded Shoulders - shoulders which are excessively forward are more likely to have rotator cuff injury, as well as pressure onto the biceps tendon as it enters the upper arm. This can often lead to biceps tendonitis, and or rotator cuff tendonitis. It can be due to tightness in the front of the shoulders, or pectoral muscles, and result in poor posture or mechanics when moving the arm. This causes the bone of the upper arm to put pressure on the structures on the front of the shoulder, and causes pain in that area, especially when lifting or carrying something with a bent elbow. Excessive rounding of the shoulders can also place the rotator cuff tendons and bursa in a position where they can become pinched between the upper arm and the acromion process of the shoulder blade (bony prominence beside the collar bone), known as impingement.
- Postural Malalignment - poor posture, particularly a "chin-poke" posture (head forward with chin leading) with rounded shoulders, puts excessive pressure and tension through the trapezius, located between the shoulder and the neck. In addition, it leaves the rotator cuff tendons in jeopardy of impingement. It can also lead to nerve compression at the neck which can refer pain to the shoulder. As we age and the upper back becomes more rounded and rigid, it is anatomically impossible to raise the arm up above the head (try standing with poor posture and lifting your arm up to 180º, repeat again after regaining optimal posture with the "heart lifted"). Consider this when you are younger and still have good mobility in your upper back - the more rigid you become at a younger and still have good mobility in your upper back - the more rigid you become at a younger age, the more likely you are to have limited movement in the shoulder. Tackle it now.
- Joint Stiffness or Arthritis - as we age, particularly if there has been a previous injury to the shoulder, there is a tendency for the joints of the shoulder to stiffen. Aside from the glenohumeral (ball and socket joint between the large upper arm bone and the shoulder blade), we also rely on mobility at the AC joint between the shoulder blade and the collar bone to raise the arm overhead. The AC joint is commonly affected by arthritis and joint stiffness and can lead to pinching or sharp pain above the shoulder joint. The glenohumeral joint can also become stiff and "grinding" can be felt, and often heard, when the arm is moved.
As you can see, there are many different potential causes of pain or limited function at the shoulder, and it is best to receive an appropriate diagnosis and treatment plan after a complete orthopaedic assessment by a physiotherapist so you can receive appropriate hands on treatment as well as exercise to reduce the chance of reinjury and ongoing pain.