Muscle guide · Chest and shoulders
Also called back rotator cuff muscle, back of the shoulder blade muscle
The infraspinatus is the thick, triangular rotator cuff muscle that covers much of the back of your shoulder blade, below its bony ridge. Its tendon crosses the back of the shoulder joint to the outer bump of the upper arm bone, just behind the supraspinatus.
It is the main muscle that turns your arm outward, and it also helps lift the arm and keep the ball of the joint centred. Its nerve winds round a notch at the edge of the shoulder blade, which is why the muscle can waste on its own, often without pain, in volleyball players and other overhead athletes.
When its nerve was blocked, volunteers lost about 70% of their strength turning the arm outward and about 45% of their strength lifting it out to the side, at every angle tested. That was one nerve-block study in 11 volunteers (read as an abstract); lasting injuries may differ. A review of shoulder exercise studies also credits it with much of the force for raising the arm in the plane of the shoulder blade.
In volleyball, its nerve is stretched as the arm cocks back and follows through on the serve, which is thought to explain the wasting seen in some players. A systematic review found the wasting far more common in overhead athletes than in the general population.
At 10 to 40% of maximum effort the infraspinatus did more of the work of turning the arm outward relative to the deltoid, and lightly pressing the elbow into the side reduced the middle deltoid's share. Heavier efforts brought in more deltoid.
Source 8
The first moves are ordered by EMG (electromyography, a recording of muscle activity), which shows activity, not growth. Side-lying external rotation drew the most infraspinatus activity of seven exercises in one study, and the bench version is the same movement; standing and face-down rotation were also measured but worked it less. The Cuban rotation and face pull are chosen from its action. Keep the load light.
3D demoSide-lying external rotationBeginner · A dumbbell
3D demoSide-lying dumbbell external rotation (on a bench)Beginner · A dumbbell + A bench or box
3D demoStanding band external rotationBeginner · A band + An anchor point
3D demoProne dumbbell external rotationIntermediate · A dumbbell + A bench or box
3D demoCuban rotationIntermediate · A dumbbell + A band
3D demoFace pullIntermediate · A bandIn a trial in people with a tight back of the shoulder, the cross-body stretch improved inward turning by 20 degrees in 4 weeks, while the sleeper stretch's gain was not significant. In the lab the cross-body stretch softened the infraspinatus only when the shoulder blade was held still, so brace that shoulder blade against a wall or door frame.
Wasting of the infraspinatus alone usually means its nerve is compressed or stretched at the spinoglenoid notch, sometimes by a small cyst; wasting of both the supraspinatus and infraspinatus points higher up, to the notch at the top of the shoulder blade. Suprascapular nerve problems account for about 1 to 2% of shoulder pain, and up to a third of it in overhead athletes.
Compression at the lower notch is often painless. In 96 top volleyball players, 12 had painless wasting with about a fifth less outward-turning strength, and when followed for over 5 years most were still playing with the wasting unchanged. Most people improve with non-surgical care over 6 to 12 months, though marked wasting may not fully recover, and new wasting or weakness should be checked.
Infraspinatus tears usually extend from supraspinatus tears, and worn tears most often sit near where the two tendons meet. Weakness turning the arm out, or an arm that drops back when placed turned out, suggests the infraspinatus is involved; in one study this dropping sign matched advanced infraspinatus damage in all 54 people examined.
Pain when turning the arm outward against resistance is one of the more useful signs of rotator cuff pain under the tip of the shoulder, and problems at the back of the cuff made up a third of painful arcs in an older series.
For a large dent left in the back of the ball of the arm bone after a dislocation, one operation (a remplissage) fills it with the infraspinatus. Older people who dislocate a shoulder are prone to rotator cuff injuries.
Source 16
With the supraspinatus, the infraspinatus is where most rotator cuff calcium deposits form.
Source 17
Each grade rates the evidence for the correction.
One examiner found active trigger points in the infraspinatus of 77% of 72 people with chronic shoulder pain. But across studies, examiners agree only moderately on where trigger points are, and a meta-analysis judged finding them by touch unreliable. A 12-week programme treating them beat a waiting list, without a placebo comparison.
In volleyball players the wasting was often painless and most kept playing for years, and a systematic review found no convincing link with performance or other shoulder damage. New wasting still needs checking.
It is the other way round: compression or stretching of the suprascapular nerve causes the wasting and weakness.
A 25-minute band routine for healthy shoulders: move the shoulder and upper back through their range, then strengthen the rotator cuff and shoulder blades.
25 minBeginner12 movesA wall, A bandA 30-minute antagonist workout for climbers: push-ups and presses, band rotations, Y-T-W raises and face pulls, wrist and finger extensions, and a side plank.
30 minBeginner13 movesA band, A dumbbellA 12-minute warm-up for tennis, padel, squash or badminton: skipping, leg swings, trunk turns, band shoulder work, forearm circles, shuttles and landings.
12 minBeginner10 movesA wall, A bandA 25-minute low-load routine for hypermobile joints: hip, trunk and shoulder control plus balance, done slowly in the middle of your range.
25 minBeginner15 movesA bench or box, A wallIt is the main muscle that turns your arm outward, and it helps lift the arm and keep the ball of the shoulder centred. In one study that temporarily numbed its nerve in 11 volunteers, they lost about 70% of their strength turning the arm out and about 45% lifting it to the side, though lasting injuries may differ.
Side-lying external rotation: of seven exercises measured, it drew the most infraspinatus activity. Keep it light, because at 10 to 40% of maximum effort the infraspinatus did more of the work compared with the deltoid, and lightly pressing the elbow into your side helped.
Rotator cuff pain is usually felt on the outside of the shoulder and upper arm, worse lifting the arm and at night lying on that side. Trigger points in the infraspinatus are said to send pain elsewhere, but examiners agree only moderately on finding them.
Wasting of the infraspinatus alone usually means its nerve is being squeezed or stretched where it winds round the edge of the shoulder blade, sometimes by a small cyst. It is common in overhead athletes and often painless, but new wasting or weakness should be checked by a clinician.
Often not. In one study, 12 of 96 top volleyball players had painless wasting, and over 5 years most kept playing with the wasting unchanged. A review found no convincing link with performance or other shoulder damage.
The evidence is mixed. One examiner found them in the infraspinatus of 77% of people with chronic shoulder pain, but examiners often disagree on where trigger points are. A programme treating them did better than a waiting list, but that trial had no placebo comparison.
Try the cross-body stretch, which improved inward turning by 20 degrees in 4 weeks in a trial. In the lab it softened the infraspinatus only when the shoulder blade was held still, so lean that shoulder blade against a wall or door frame. Taking the hand behind your back with the arm turned in also eased it after about 20 seconds.
Yes, usually when a supraspinatus tear spreads backwards, since worn tears most often start near where the two meet. Weakness turning the arm out, or an arm that drops back when placed turned out, suggests the infraspinatus is involved.
The suprascapular nerve, from the C5 and C6 nerve roots, sometimes with C4 too. It also supplies the supraspinatus and reaches the infraspinatus through a notch at the edge of the shoulder blade.
Anatomy and movement education, not a diagnosis or treatment plan. If you have pain that follows an injury, is severe or getting worse, or comes with numbness, weakness or swelling, get it assessed. Health disclaimer.
