Infraspinatus is a muscle in the human body. It is triangular in shape and occupies the chief part of the Infraspinatus fossa. The function of this muscle is to help the arm rotate externally and stabilize the shoulder joint.
It is one of the four rotator cuff muscles that crosses the shoulder joint and is commonly injured.
It is located behind the shoulder and covers the shoulder blade. This muscle attaches in a medial manner to the infraspinous fossa of the scapula. It attaches laterally to the middle facet of the greater turbercle of the humerus. The muscle arises as fleshy fibers from the medial two-thirds of the Infraspinatus fossa and as tendinous fibers from the ridges on its surface. It also originates from the infraspinatous fascia which covers it and also separates it from the teres major and teres minor.
Picture 1 - Infraspinatus
The tendons of this muscle are sometimes separated from the capsule of the shoulder joint by a bursa which communicates with the joint cavity of the arm.
The fibers of this muscle converge into a tendon that glides over the lateral border of the spine of the scapula and pass across the posterior part of the capsule of the shoulder joint. It is inserted into the middle impression on the greater tubercle of the humerus. The trapezoidal insertion of the Infraspinatus into the humerus is larger than the equivalent insertion of the supraspinatus. This is the reason why the Infraspinatus is connected with rotator cuff tears. The suprascapular nerve innervates the supraspinatous and infraspinatous muscles. These muscles help to abduct the arm and laterally rotate it.
The main function of the muscle is horizontal or transverse extension and lateral rotation of humerus at the shoulder joint. It is the major force behind the external rotation of the shoulder. When the arm is fixed, it abducts the inferior angle of the scapula. The Infraspinatus and the teres minor help in rotating the head of the humerus outward direction. They also assist in carrying the arm backward which is the extension of the glenohumeral joint. The Infraspinatus reinforces the capsule of the shoulder joint.
An injury to the infraspinatus can take place due to over usage or repetitive motion of the muscle along with the supraspinatus. Sports that require heavy usage of the muscle may cause damage to it, for example baseball, swimming and tennis (where the arm is rotated a lot). Activities such as driving or using a computer, where the arm is not supported, may also become the reason behind the injury of infraspinatus muscle.
There are two types of injury which normally occurs in the Infraspinatus:
Since the infraspinatus tendon has a poor mechanical advantage, it is a relatively weak muscle in majority of the people. Sudden heavy exertion or pull can strain it and the muscle might get torn. The lesions, tissue damage may be a minor strain for some people. However, this minor strain may lead to a more severe injury in future if it does not heal properly.
Tendon joins muscle to the bone and is the main ‘pull’ of the muscle. When one damages the tendon, the muscle pulls away the tendon from the bone and the region of joint turns sore. The attachment of the tendon to the bone is quite weaker, the reason why it breaks down. Tendinitis usually occurs at the shoulder. Only a few selected arm and shoulder movements hurt.
It is generally caused due to overuse of the shoulder muscles and the pain is felt at the back of the shoulder. The pain is felt especially when one is trying to make an outward movement against some kind of resistance when a pinch of pain may be felt at the shoulder length.
Certain symptoms indicate an injury in the Infraspinatus. These involve:
Patients experience difficulties in movements while putting on a jacket. Lying on the affected shoulder while sleeping can be hurtful.
Pain spreads down into the bicep muscles. Sufferers feel as if the pain arises from deep within the joint. Side shoulder, neck and shoulder blade can also hurt.
Shoulder and arm get tired more often on one side than the other. Affected individuals also begin to feel muscle imbalance and stiffness. Sufferers often experience numbness in their arms.
The above pain and aches worsen at night particularly and make sleeping difficult. Other symptoms include such as the pain developing gradually, no pain when the arm is at rest and selected arm movements are extremely painful.
The treatment for this condition aims at providing patients with relief from the painful symptoms. It is usually recommended when rest and exercise do not heal the injury. However, delaying the treatment can lead to frozen shoulder as the other muscles try to compensate for the injury of the infraspinatus.
Picture 2 - Infraspinatus Image
These are some of the treatment options that should be followed:
Trigger points are knots in your muscles which are caused due to stress which leads to shortening and stiffening of muscles. Too much of movement stresses muscle attachments and damages the joints. Popping shoulder joints are evidence of joint stress caused by trigger joints.
To remove the knots you can do the following:
Massage your shoulder blade with the help of a tennis ball against a wall. You should do a minimum of 20 strokes several times a day.
The Rhomboid can also get overworked which lies between the shoulder blade and spine. You must massage the Rhomboid using a ball.
Correct your posture when sitting and doing exercises like Barbell Rows or Bench Press. Hanging shoulders or flaring shoulder blades is a bad posture.
Exercises that can you can do to heal your shoulder muscles are:
This is done as sometimes problems of shoulder imply problems of your hips. One must check for symptoms of Lordosis.
Improve upper body movements is a must. You can do 3×10 reps as warm up session when you are beginning to recover. Start with a wide grip.
Try to strengthen you upper back and straps. Squeeze your shoulder blades when pulling back. Carry out 3×10 respiratory exercises after workout.
Tight chest muscles will tend to pull your shoulders down. Therefore, perform 3 sets of 10 seconds of chest exercise after workout and on the days when you are recovering from the injury.
Some of the other treatment approaches that you can go for are:
If the tendon tear is not too large then you can do friction treatment for about 4 to 6 weeks and the results are usually very good. This therapy reduces the growth of adhesive tissues and helps the tendon to heal quickly.
One or two corticosteroid injections are usually helpful. The injection is part of a long-term treatment for a prolonged injury. Ultrasound-guided injections yield the maximum benefit with minimum risk.