The shoulder is a complex region made up of many key structures such as the glenohumeral joint (the true shoulder joint) and the scapular (shoulder blade). The glenohumeral joint facilitates over half of this movement and allows the large range of movement in all directions, that is unique to the shoulder. This movement is allowed by the shallow socket (glenoid) which the upper arm (humerus) articulates with. However, due to this anatomy allowing movement the shoulder sacrifices its stability within the joint itself, meaning there is a complex arrangement of joints and soft tissue structures which can become injured and cause shoulder pain. The structures include:
Bursa, which are fluid filled sacs which reduce friction between bone and soft tissue.
Rotator cuff muscles: small stabilising muscles which initiate certain movements of the shoulder and helps depress the humerus inside the glenoid (keep the ball in the socket of the shoulder joint).
Long head of biceps tendon: Inserts into the shoulder as well as has an attachment to the labrum (cartilage), which commonly becomes injured in throwing athletes.
What is impingement:
Above the glenohumeral joint is a bone called the acromion which is a part of the clavicle (depicted below), this creates a roof over the shoulder joint. Below the under-surface of the acromion and the top of the shoulder forms the subacromial space (depicted below). In this space lies the long head of biceps tendon, the supraspinatus tendon and the subacromial bursa. All these soft tissues are in a small anatomical space and can rub against the above acromion, causing irritation and pain.
What causes impingement?
Shoulder impingement is generally caused by the structures (bursa, biceps long head tendon and supraspinatus tendon) becoming inflamed. This inflammation reduces the space within the subacromial space, particularly with movements bringing the arm up to the side, causing these already irritated tissues to get pinched under the acromion. These structures are often inflamed by activities which involve sustained and repeated overhead movements, such as a tradesperson lifting above head or a cricket bowler. Poor forward sitting posture which includes rounded shoulders can also cause irritation to these structures.
Less commonly shoulder impingement can be secondary to dysfunction of other structures. This includes instability of the shoulder joint itself leading to the humerus moving up in the socket (glenoid), poor scapular movement and control (scapular dyskinesis) and loss of internal rotation of the shoulder after doing throwing sports, such as baseball, which involves excessive and loaded external rotation movement.
Signs and symptoms:
Pain with movement, particularly when moving the arm up and down to the side
Muscle spasm in the neck and back muscles
Reduced shoulder range of movement
Rounding of the shoulders, particularly with sitting
Physiotherapy treatment will include a combination of manual therapy and exercise prescription to reduce pain, improve flexibility, movements patterns and restore function.
We will also look at what other factors may be contributing to pain and altered shoulder movement patterns, such as sitting posture and lifting techniques at work or the key biomechanics of the sport. Physiotherapy management may also involve treating other areas of the body such the neck or upper back, which may also be affected as well as advice on other aggravating activates such as completion of tasks around the home, hobbies, or sleeping position.
Importantly we will look to include a home exercise program which targets strength, mobility, and motor control to ensure efficient movement of the shoulder is regained. This is done by addressing the weakness of shoulder stabilising muscles which is essential in the smooth interplay of the many structures which allow so much range of movement within the shoulder.