What is an impingement syndrome?
A shoulder impingement syndrome is a condition where the tendons of your rotator cuff muscles become pinched or compressed with certain movements in the shoulder. This, in turn, aggravates and damages the tendons and bursa (a fluid-filled cushion-like structure) which results in pain and inflammation. Some people with shoulder impingements find it difficult to perform daily tasks such as: putting on a seatbelt, getting dressed, raising arms above one’s head or exercising the arms (particularly overhead movements). 
Prolonged impingement can lead to tendonitis or tendinosis of the rotator cuff tendons (particularly the supraspinatus) and/or bursitis (inflammation of the bursa). Calcific tendonitis (bone forming in the tendon) may also occur, and if not treated early, partial or complete tears of the supraspinatus tendon can occur, which usually requires surgical repair.
What causes an impingement syndrome?
First… some anatomy:
Place your hand on the outer top part of your shoulder and feel for a bony prominence. This bony point of the shoulder is called the acromion. The supraspinatus muscle passes underneath the acromion in the subacromial space and this is where the impingement occurs:
Now that we have a visual idea of the structures, lets explore the two different types of impingement syndromes that can occur: Primary and Secondary.
Primary Impingement Syndrome
The size of the subacromial space varies from person to person. Some people are born with a smaller subacromial space, while others may become smaller due to osteoarthritis later on in life. In both instances, the structures in the subacromial space are likely to become compressed and inflamed which results in an impingement syndrome.
Secondary Impingement Syndrome – Shoulder dyskinesis
Instability and dyskinesis in the shoulder can lead to improper shoulder movements. In a dynamically unstable shoulder, ligament laxity and muscle weakness can occur. The underlying cause is usually repeated overhead activity (painting or playing sports such as tennis), poor posture or from an old shoulder injury that was not rehabilated correctly.
The instability in the shoulder also results in the rotator cuff muscles working harder and eventually becoming fatigued. The rotator cuff normally functions to stabilize the glenohumeral joint but holding the head of the humerus against the glenoid fossa of the shoulder blade. When the rotator cuff begins to fail, the shoulder often hikes up which compresses the structures previously mentioned against the subacromial space.
Symptoms of an impingement syndrome
Symptoms of a shoulder can vary depending on the severity of the condition, but can include:
- Pain or difficulty reaching behind your back
- Pain or weakness noted when trying to lift your affected arm
- Pain when lying on the affected side when sleeping
- Pain radiating from the shoulder down to the elbow or hand
- “Painful arc sign”
- Pain when performing daily tasks such as getting dressed, putting on a seatbelt or driving.
Risk factors for an impingement syndrome
Any sport, activity or occupation that involves overhead movements will likely predispose a person to impingement syndromes. In patients older than 40 years of age, have a higher rate of incidence than males.
How is an impingement syndrome treated?
Chiropractic treatment of an impingement syndrome that does not yet require surgical repair can be conservative. This would involve mobilizations and manipulations of the affected side. Soft tissue modalities such as dry needling, massage, and stretching can also be used. Correcting the underlying instability is also essential with the above mentioned modalities as well as incorporating an exercise program to strengthen the weak muscles in and around the shoulder. Posture correction will also help to keep the shoulders in a neutral position.
