The infrapinatus muscle is a thick irregular rotator cuff muscle located on the back of your shoulder blade. It has a strong connection to the shoulder and along with teres minor, rotates your arm externally. Most importantly, in conjunction with the other rotator cuff muscles, it is responsible for dynamic stabilization of the shoulder joint, especially during upward movement of your arm.

The shoulder has less connective tissue structure than other major joints. The rotator cuff muscles, including infraspinatus, act as a sort of dynamic muscle/ligament hybrid to stabilize the shoulder joint as you move.

Of the important functions of infraspinatus is to provide force to seat the head of humerus when you extend your arm up.

Trigger points in your infraspinatus refer pain deep in the front part of the deltoids, and sometimes extending down the side of your arm past the elbow to the top and thumb side of your forearm and hand. Infraspinatus can also cause pain on the inside edge of your shoulder blade.

Infraspinatus trigger points are often involved with shoulder impingement syndromes and subacromial pain syndrome. Trigger point referrals from infraspinatus can initiate central sensitization leading to chronic shoulder pain.

Trigger points in the infraspinatus often cause pain even when you are at rest, as well as interfering with your daily activities and sleep. You may experience a deep ache in the front of your shoulder or deltoids that feels deep in the joint. It can be similar to bursitis. Pain can spread down your arm past the elbow and to the top and thumb side of your forearm and hand. It can even include the fingers and thumb. This pain can be similar to a C5-C6 cervical issue or carpal tunnel syndrome. In fact, some studies have found that a third of patients with suspected of carpal tunnel syndrome and EMGs negative for carpal tunnel have infraspinatus trigger points. Others have observed generally that treating infraspinatus trigger points reduces symptoms of carpal tunnel syndrome. You may also experience significant pain on the inside border of your shoulder blade or pain extending up the side of your neck. Infraspinatus trigger points can contribute to symptoms of mechanical neck pain, post-mastectomy pain, office and industrial workers, or those with a medical diagnosis of subacromial impingement syndrome. Infraspinatus trigger points contribute to shoulder girdle fatigue, weakness of grip, loss of should mobility and increased underarm sweating. Common compaints include:
  • I can't reach my back pocket
  • I can't fasten my bra behind my back anymore
  • I can't reach into the back seat of my car
  • I have to put my coat on one sleeve at a time
  • I can't play overhead sports
If your infraspinatus trigger points are on your dominant side you may have difficulty with reaching your head to comb, brush or dry your hair, brush your teeth, apply makeup or shave facial hair. However, if the trigger points are on your non-dominant side, you may not notice even moderate restrictions unless you make movements that are unusual for you. If you have infraspinatus trigger points you may find that sleeping on the involved side is painful. However, sleeping on the uninvolved side can also cause problems. The pressure of your upper body may cause pressure on the 'good' side and activate trigger points in the infraspinatus on that side. In addition, the upper, painful arm falls forward, causing a prolonged stretch of the infraspinatus, re-activating the originally painful side. Some people find that they need to sleep in a reclined position until their infraspinatus trigger points moderate. Note that a similar mechanism can occur during surgery. Trigger points in the infraspinatus and other muscles can be activated by sustained pressure or awkward positions during surgery. Patients who have suffered a stroke and are paralyzed in the shoulder girdle on one side experience significant pain. This is because various muscles develop trigger points on the affected side, including the infraspinatus, supraspinatus, subscapularis, trapezius, levator scapula, rhomboids and deltoids. If the muscles are not spastic, they respond well to individual treatment of trigger points.
When a posture or activity that activates a trigger point is not corrected, it can also perpetuate it. Trigger points can be activated anywhere in the infraspinatus from unaccustomed eccentric loading, eccentric exercise in an unconditioned muscle, maximal or sub-maximal concentric loading. Placing the muscle in a shortened or lengthened position for an extended period of time can also activate trigger points in the infraspinatus. Infraspinatus is most often activated by major acute or minor repetitive overload. For instance, frequently reaching to the back seat of a car to tend to an young child is a repeated minor overload. Losing your balance going down the stairs and suddenly reaching back for the railing is a more significant acute overload. Vigorous weight training with heavy overhead loads is a continued, but acute overload. Other examples of acute overload include twisting your arm when falling holding a ski pole, a hard tennis serve delivered when slightly off balance or dragging a novice ice skater, luggage or wagon around for a long time. In acute cases, the onset of pain is usually within a few hours of the trauma. You will usually be able to identify the event. Accident? Get Treatment ASAP! Following their first moving vehicle accident, 20% - 30% of individuals developed infraspinatus trigger points, regardless of the direction of impact, a slightly lower rate than the development of supraspinatus trigger points. In cases of chronic shoulder pain and dysfunction, studies have shown an improvement of 24% in DASH scores (Disability of Arm, Shoulder and Hand) as active trigger points were inactivated. In all there was a 55% improvement pain and function at 12 weeks. Elite swimmers with shoulder pain had significant trigger points in the infraspinatus and subscapularis muscles that reproduced the swimmer's pain. They found active trigger points, inducing referred pain, in the shoulders of swimmers without shoulder pain too. However, when questioned, the swimmers said they recalled having that pain. Repetitive overuse and overload of the rotator cuff muscles, especially infraspinatus, is also associated with competitive volleyball. Release of those trigger points quickly restored active range of motion and allowed disabled athletes to return to competition.
backknobber self care trigger pointThe infraspinatus muscle can be access easily with a tennis or lacrosse ball. In addition, for more precise location of trigger points you can release infraspinatus yourself using a tool such as the Back Knobber.