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The shoulder joint is a ball and socket joint with the most flexibility of any joint in our body. This allows for incredible range of motion in flexion, extension, abduction, adduction, internal and external rotation. On the downside, such flexibility leaves the joint itself unstable. It is the work of the rotator cuff muscles, along with tendons and ligaments to provide the stability it needs.
There are 3 bones that make up the shoulder joint: the humerus, the scapula and the clavicle. The articulations between these bones make up 4 different joints in the shoulder.
The glenoid labrum is fibrocartilage that is attached to the inside of the glenoid fossa. It provides additional depth and support that contributes to the overall stability. It is an attachment for ligaments and is continuous with the long head of the biceps brachii.
If the labrum gets torn, symptoms include:
- A deep aching pain that is difficult to pinpoint its location
- Weakness in the shoulder joint
- Popping or clicking in the shoulder
- Pain reaching overhead
There are several bursae sacs in the shoulder joint. This is necessary to prevent friction with such great movement. The most commonly irritated bursa is the subacromial bursa, due to its location under the acromion process of the scapula.
Bursitis occurs when a bursa becomes inflamed due to various reasons (shoulder impingement caused by muscle imbalances, autoimmune disorders, infections). Subacromial bursitis often accompanies Rotator Cuff Tendonitis. The symptoms of shoulder bursitis are localized swelling and tenderness in the area of the bursa, and pain when moving the arm out to the side.
- Coracoclavicular ligaments
- Coracoacromial ligament
- Coracohumeral ligament
- Glenohumeral ligament
These ligaments are very important for the stability of the shoulder and also a source of pain when they are damaged. There are 3 grades of sprains, going from mild to severe damage. Symptoms will vary depending on how bad the injury is. Immediately after the injury there will be swelling around the top of the shoulder and the damaged ligament will be painful to touch. If the injury is severe, there will be a lack of stability in the shoulder joint.
Rotator Cuff Muscles
The supraspinatus muscle is most frequently injured, followed by the infraspinatus muscle. Active trigger points in any of these muscles can also cause a great deal of pain.
Each muscle presents with its own set of symptoms when injured or carrying active trigger points.
Supraspinatus– Pain is located in the upper shoulder and in the area of the AC joint. Regular activities become difficult, such as brushing teeth, shaving and throwing a ball.
Infraspinatus– There is pain and restriction of reaching backward. The movement is similar to reaching the back pocket, or for females reaching to fasten the bra. The pain is located on the front or side of the shoulder. There may be pain sleeping on the affected shoulder. The infraspinatus muscle can be damaged in sports throwing a ball (baseball) or through direct trauma. Long hours at a computer and driving can also aggravate this muscle.
Teres minor– This muscle is less frequently injured, but active trigger points can cause pain that is on the back of the shoulder.
Subscapularis– The most evident pain with subscapularis involvement is when the arm is in the position as if you were going to throw a ball. As the arm is moved backwards, the pain appears on the front of the shoulder where the muscle attaches.
Supraspinatus trigger points (left) cause pain on the shoulder and down the arm, sometimes with sharp pain at the elbow. The pain can appear when bringing the arm out to the side or reaching above your head.
Infraspinatus trigger points (right) cause pain on the front and side of the shoulder. The pain may refer all the way into the hand and even to the base of the skull on the same side.
The teres minor trigger point (left) refers pain to the back of the shoulder and upper arm.
Subscapularis trigger points (right) can cause pain on the back of the shoulder, back of the wrist, on top of the shoulder and down the back of the arm. This muscle can be very involved in cases of Frozen Shoulder.