Anatomy of the Shoulder

 

The glenohumeral joint, also know as the shoulder joint, is a ball and socket style joint that is responsible for connecting the upper extremity to the trunk. It is one of four joints that comprise the shoulder complex and will be the focus of this article. The shoulder joint is formed as the head of the humerus sits in a shallow socket on the side of the scapula (shoulder blade) known as the glenoid fossa.

The shoulder joint has been likened to a golf ball sitting on a golf tee and also a ball balancing on a seals nose. This anatomic make up allows for a great range of motion. Unfortunately what the shoulder has in mobility it lacks in stability. Unlike the hip joint where the head of the femur sits in a deep socket within the pelvis, the humeral head has minimal contact with the scapula. A rim of cartilage called the glenoid labrum attaches to the periphery of the socket enhancing the depth of the socket by approximately 50% adding to the joints stability. A shoulder dislocation will invariably tear a portion of the labrum leading to a reduction in stability and increased chance of recurrence

 

The glenohumeral joint, also know as the shoulder joint, is a ball and socket style joint that is responsible for connecting the upper extremity to the trunk. It is one of four joints that comprise the shoulder complex and will be the focus of this article. The shoulder joint is formed as the head of the humerus sits in a shallow socket on the side of the scapula (shoulder blade) known as the glenoid fossa.

 

The shoulder joint has been likened to a golf ball sitting on a golf tee and also a ball balancing on a seals nose. This anatomic make up allows for a great range of motion. Unfortunately what the shoulder has in mobility it lacks in stability. Unlike the hip joint where the head of the femur sits in a deep socket within the pelvis, the humeral head has minimal contact with the scapula. A rim of cartilage called the glenoid labrum attaches to the periphery of the socket enhancing the depth of the socket by approximately 50% adding to the joints stability.  A shoulder dislocation will invariably tear a portion of the labrum leading to a reduction in stability and increased chance of recurrence.

 

The shoulder is surrounded by a capsule that is reinforced by a group of ligaments. Running through the capsule and attaching to the top of the shoulder is the long head of the biceps tendon.  Additionally, there are a few bursas that sit in and around the shoulder and the most integral one is the subacromial bursa that sits below the top of the scapula to help alleviate friction from the moving shoulder.

 

As there is a distinct lack of structural stability, the shoulder joint relies heavily upon dynamic stabilisation provided by the rotator cuff muscles. The rotator cuff is comprised of four muscles that sit on the scapula and attach to the head of the humerus. These muscles are the supraspinatus, infraspinatus, subscapularis, and the teres minor. 


The rotator cuff can be injured traumatically or as a result of degenerative changes. One of the most common shoulder problems addressed at SquareOne Physiotherapy is shoulder impingement. Any dysfunction of the rotator cuff will lead to abnormal shoulder mechanics and can lead to subacromial impingement. Structures such as the subacromial bursa, long head of the biceps tendon, and supraspinatus tendon can get compressed leading to pain and inflammation. Rehabilitation involves postural correction, addressing muscular imbalances, hands on therapy techniques and dry needling, strengthening of the rotator cuff, exercises aimed at improving the dynamic relationship between the humerus and the scapula, advice and education, and traditional rigid or kinesio taping.


Should you have any issues with an acute or ongoing shoulder problem, contact the team at SquareOne Physiotherapy for an accurate diagnosis so an appropriate rehabilitation program can be commenced.