There are many conditions that can result in shoulder pain. Some include the more traumatic ones like fractures, subluxations, tears in the rotator cuff muscles or the labrum (a structure that forms the socket) through an injury. The much more insidious shoulder pain are a frozen shoulder and shoulder impingement syndrome.
We will discuss the mechanical causes of a shoulder impingement syndrome, also referred to as subacromial impingement syndrome.
What Is An Subacromial Impingement Syndrome?
An impingement syndrome results in pain and movement impairment. This is when certain tissues are being impinged or compressed between two bony structures. One of the most common shoulder impingement occurs in the space under the acromion (see picture).
The impingement is most significant when the arm is elevated sideways to about 90 degrees. The structures that are impinged are soft tissues that lie under the acromion. These are your supraspinatus tendon (which is part of the rotator cuff), the subacromial bursa. The pain felt can also be magnified by the irritation of the ligaments that surrounds the area. An untreated subacromial impingement can eventually result in a tear in the Supraspinatus tendon.
What Are The Contributing Factors?
The cause of an impingement is anything that reduces the space through which the soft tissues lie. A structural fault such as a bony spur present under the acromion can reduce that space. However, the presence of the spur itself may not be a primary cause of the impingement. It is more often of a result of the inability of the ball (head of the humerus) staying centre in the socket and/or together with the bony anomaly in the acromion that results in the impingement. Hence, we need to look at what holds the ball centre in the socket in a normal pain free shoulder. Without it will result in space reduction in the space under the acromion.
These structures are primarily the rotator cuff muscles, specifically the Subscapularis and the Infraspinatus. These two muscles are positioned lower and their function is to provide a downward force. Together with other rotator cuff muscles, they work together to stabilize the humeral head in the centre of the socket. When the ball jams up into the acromion, this means that the ball has moved upwards. It has also moved away from the centre in the socket. This is a result of the muscle imbalance between the muscles that pull the ball up and the muscles that hold the ball down. When there is an imbalance, the ball rides up and jams into the acromion, hence reducing that space.
What’s Next For Shoulder Impingement?
If symptoms and pain persist, visit a doctor or specialist in Singapore for diagnosis and treatment advice. At Core Concepts, our team of physiotherapists will work with you to diagnose shoulder impingement. They will also recommend exercises to assist in improving your shoulder posture and strengthening muscles. The rehabilitation will also include the retraining of the lower cuff muscles- namely the Infraspinatus and Subscapularis.