Shoulder impingement syndrome is a common cause of shoulder pain. It occurs when the bones of the shoulder pinch or impinge upon the tendons or bursa in the area. The term “shoulder impingement” really covers several conditions, but multiple ailments are often involved. These conditions include biceps tendinitis, subacromial bursitis, rotator cuff tendinitis, rotator cuff tear, calcific tendinitis, RSI (mouse shoulder), arthritis and congenital abnormalities.
More specifically impingement syndrome is when one or more of the rotator cuff muscle tendons or the subacromial bursae become impinged in the subacromial space. This is the space between the head (ball) of the humerus (arm bone) and the acromial process of the scapular (shoulder blade).
Four muscles make up the rotator cuff, supraspinatus, infraspinatus, teres minor and subscapularis. These muscles are responsible for stabilising the shoulder, also controlling the movement and orientation of the humeral head within its socket. The belly of the supraspinatus muscle and its tendon pass within the subacromial space. The long-head of biceps tendon also passes through the subacromial space and acts likes a 5th rotator cuff muscle by stabilising the shoulder joint. The subacromial bursae is a fluid filled sac that sits under the acromial process between underside of the acromion and supraspinous tendon. Pain often originates from one or all of these structures.
Shoulder impingement has many possible causes. These factors may act alone or in combination..
Age – as we age, our tendons, muscles and ligaments lose strength and their capacity for tissue repair decreases.
Poor Posture – a forward shoulder posture narrows the space available for the tendons and bursae. This may result in friction damage and tissue fatigue. The forward and downward sloping of the shoulder blade, may interrupt normal blood circulation in the subacromial space; resulting in tissue damage.
Overuse/RSI – repetitive use of the arms may cause fatigue and micro-trauma to the muscles, tendons and bursae. If the rate of tissue damage exceeds the rate of tissue repair; degeneration will occur.
Muscle Weakness – muscle weakness and fatigue in the rotator cuff muscles is very common. These tissues are put under continued and maintained stress. Very few people who participate in regular exercise (weight training, swimming etc..) will perform specific rotator cuff strength and conditioning exercises. Like any muscle group, once used they should be given sufficient time to rest and recover. Muscle weakness and fatigue will also effect the mechanics within the ball and socket joint; increasing the likelihood of tissue damage.
Instability – people who are particularly mobile, have a history of shoulder dislocations or have been swimming since a young age may very lax shoulder joints. Hyper-mobility may predispose some individuals to develop impingement syndrome. The problems result from the ball not staying properly centered in the shoulder socket.
Stiffness – A fibrous joint capsule surrounds the ball and socket joint. Tightness in the posterior part of this capsule can cause the ball to move abnormally upwards on the socket. This can lead to additional friction and compression on the subacromial tissues.
Most patients can’t recall a specific incident that triggered the onset of symptoms; pain generally builds over time. Pain is worse with use and at night, commonly being felt around the outside of the shoulder and upper arm. The following features are often present:
- Pain when the arm is above head height
- Pain when the arm is raised out to the side
- Pain when reaching behind the back
- Night pain
- Pain may radiate into the neck, back or arm
In most cases, the case history and physical examination is all that is necessary to make a diagnosis. In some cases extreme pain may raise suspicion of a possible rotator cuff tear, calcific tendinitis or arthritic changes; which may result in a referral for x-ray or MRI scan.
Most shoulder impingement cases resolve with osteopathic treatment and avoidance of causative factors. Healing, especially of tendons is a slow process; it may take 4-12 weeks for symptoms to subside completely. However continued use and aggravation of the subacromial structures may result in full tendon rupture and chronic pain.
The goals of osteopathic treatment are:
- Avoidance of aggravating and causative factors
- Promote healing by improving local circulation, movement and strength
- Correction of any mechanical or postural abnormalities that predisposed to the condition
- Prevention of recurrence by the use of a home flexibility and strengthening program
Recommendations for patients with shoulder impingement
- Stop or modify activities that cause pain
- Use ice therapy to reduce pain and swelling; this is particularly important during the early stages of impingement syndrome and after treatment and exercise sessions. Apply the ice pack for 10 minutes 2-4 times a day.Do not apply the ice directly on the skin.
- Non-steroid anti-inflammatory drugs i.e. Ibuprofen will help reduce inflammation and pain. They may only be effective during the early stages of injury, when inflammation is more prevalent
- Stop smoking and take up some aerobic exercise; smoking effects the circulation to tendons, muscles and bones. Reduced circulation increases the risk of injury by slowing the rate of tissue repair. Some gentle exercise will improve overall cardiovascular health, allowing improved circulation and in turn tissue repair.