What is the supraspinatus?
The supraspinatus is a muscle which sits within the top of the shoulder blade (Supraspinous fossa). It is one of the rotator cuff muscles (supporting muscles of the shoulder) which carries out movement of the arm to the side (known as abduction) The supraspinatus is responsible for providing stability by securing the head of the humerus against the glenoid fossa (shoulder joint). Along with the deltoid muscle, supraspinatus abducts the arm and initiates movement for the first 20° before the deltoid muscle assists the movement to 90°.
So why is this muscle involved with shoulder pain?
The supraspinatus runs across the shoulder blade (scapula) and inserts in the top, outside region of the arm (humerus) The supraspinatus tendon runs in between two bony regions, the acromion (edge of the scapula) and the head of the glenoid (head of the humerus). When the arm is abducted, the space between these bones compress, reducing the amount of space the supraspinatus muscle tendon has to move. When there is an injury or a positional compromise of the shoulder, this can reduce the space even further causing further stress on the tendon.
Pain in the arc
When the arm is lifted out to the side of the body (abduction). Initially the patient may not experience any discomfort before 45°. As the arm is raised between 45°–120°, the supraspinatus tendon is under more compression between the acromion and the humerus. As the arm is raised to 180°, the arm will feel more comfortable, as the palm of the hand turns inwards (External rotation of the humerus). This is due to the bony landmark that sticks out of the humerus the (greater tuberosity) moving away from the supraspinatus tendon and allowing more space for the tendon to move through the subacromial space.
Testing for shoulder impingement
The ‘painful arc’ is one of the tests carried out to assess whether there is pain as the arm is raised into abduction. The test is positive if pain is experienced between 45°-120°. There are a number of additional tests that can be carried out to investigate the shoulder pain, which may include the Hawkins, Neer and Jobe test.
Other contributing factors to shoulder pain
Within the subacromial space, there are a number of surrounding structures, that can be contributing to shoulder pain. This may include involvement of the bursae. Bursae are fluid filled sacs that are responsible for reducing frictions between moving parts in your body., There are six bursae around the shoulder. One of the bursae above the supraspinatus is called the subacromial bursa. The bursa sits under the acromion and above the supraspinatus tendon. As the tendon is pressed between the bone landmarks the tendon also squashes the bursa. Repeated movement of raising the arm can further irritate both the tendon and bursa It can lead to secondary conditions, such as a sub acromial bursitis (Inflammation of the burse sac). At this stage, pain can then be further increased and movement then limited. The supraspinatus is also responsible for maintaining position of the glenohumeral joint. If the supraspinatus is injured, the other rotator cuff muscles will have to take the slack of maintain joint stability. This can lead to the rotator cuff muscle being worked harder, causing fatigue and long term could cause problems for the other rotator cuff muscles.
What’s posture got to do with it?
Sedentary lifestyle such as desk work can be a contributing factor to poor posture. Given the amount of time sitting at a desk in front of a computer can be anything up to eight hours. Throughout the day our posture can gradually become slumped in our lower back, which in turn drops the shoulders forwards to counter balance our body weight. This causes the shoulder blades to draw forwards (protraction). Over time this affects the muscles, both in the front of the chest and around the shoulders and neck. With the shoulders maintaining more of a protracted position, this can lead to the misalignment of the shoulders. This means that each time the arm is abducted, it’s more likely to cause irritation and over time cause increased wear and tear and even inflammation.
As well as considering the Supraspinatus itself, it is important to also consider associated structures and tissues, including mobility of the thoracic spine and neck. These areas can also be contributing to shoulder problems. If the thoracic spine is forward positioned (kyphosis) this can change the position of your shoulders blades which can lead to further compromise of the supraspinatus muscle. Improving movement through the thoracic spine can help to maintain better posture allowing the chest to push forwards and shoulder blades to retract. This can help the supraspinatus tendon to run freely between the acromion and glenoid head.
Osteopathy can help with shoulder pain by improving the quality of the supraspinatus muscle through soft tissue manipulation, as well as looking at improve joint mobility or the shoulder complex and surrounding areas, such as the thoracic spine. This can include gentle articulations of the thoracic spine and or spinal manipulation to encourage movement of the thoracic joints. Other treatment modalities may include Laser Therapy treatment, which is an effective way to treat the inflammation of the tendon and the bursa. Other treatments that are effective include the Graston Technique, which is an instrument assisted soft tissue technique (IAST) that works by breaking down restrictions and scar tissue that can form. The Graston Technique can help to improve and restore movement and soft tissue quality.
As well as treatment, strengthening the muscles in the back and shoulders can help with pulling back the scapulae. As well as strengthening muscles, stretching the chest muscles (pectorals) and improving mobility in the thoracic spine can further help with aligning the shoulders.
If you are suffering with shoulder pain, contact Kinesis clinic to arrange an appointment with our OSTEOPATH JASON BIANCHI.