Side-lying external rotation works the muscles at the back of the shoulder that turn your arm outward (part of the rotator cuff). You lie on your good side with the top elbow bent and resting on your side, then turn the forearm up toward the ceiling and lower it again. The only resistance is gravity, which is why it often comes before a band or a weight in shoulder rehab.

How to do the side-lying external rotation

Lie on the side that does not hurt, with your legs straight and stacked. Rest your head on your bottom arm, or on a pillow if that is easier on the neck.
Bend the elbow of your top arm to a right angle and rest the upper arm along your side. Let the forearm lie across your stomach, hand near the mat.
Keep the elbow pressed to your side and turn the forearm up toward the ceiling, like a door swinging open.
Go as far as is comfortable. In the video the forearm ends up pointing about straight up.
Lower the forearm slowly back across your stomach and repeat.

What you should feel

Work at the back of the top shoulder and around the shoulder blade. Your neck and the top of the shoulder should stay relaxed.

Common mistakes

Lifting the elbow off your side to get the hand higher.
Rolling your body backward as the forearm turns up. Keep your hips and shoulders stacked.
Letting the forearm drop back down instead of lowering it with control.
Shrugging the top shoulder toward your ear.

How often

Many programs start with 2 to 3 sets of 10 to 15 slow repetitions, once a day, with no weight in the hand. Your physio will adjust this.

Stop and check with your physio if

You feel a sharp pain or a catch in the shoulder as the forearm turns up.
Pain or tingling spreads down the arm.
Pins and needles in your arm or hand that do not go away after you stop, or part of your arm or hand goes numb. Get medical advice the same day. If one side of your face or body suddenly goes numb or weak, or your speech becomes slurred or muddled, call emergency services, even if it goes away.
The shoulder feels loose, as if it might slip out, as the forearm turns up.
A sudden pop or tearing feeling in the shoulder that brings sharp pain, new weakness or trouble lifting the arm. Stop and contact your surgical team the same day, or get medical advice the same day if you have not had surgery.
The shoulder feels as if it has slipped out of place, looks a different shape or suddenly locks so you cannot move the arm, or your hand turns cold, pale or blue. Go to an emergency department straight away, without driving yourself, and do not try to put the shoulder back in yourself.

From the clinic

The effort is greatest halfway up, when the forearm is level with the floor, and it eases as the arm nears upright. There is no need to push past upright. A small rolled towel tucked between the elbow and your side gives the elbow something to stay against. Once the repetitions feel smooth and easy, many programs add a light dumbbell or a small water bottle in the hand.

If lifting the forearm against gravity is too much for now, isometric shoulder external rotation works the same muscles without the arm moving. Standing shoulder external rotation with a band is another common way to train this direction.

After shoulder surgery, including a rotator cuff repair, or after a shoulder fracture or dislocation, follow your surgeon's or physio's plan, and do only the movements and range they have cleared. Many plans allow only passive movement at first, where the arm is moved for you and its muscles stay relaxed. Turning the arm out against any resistance, even the weight of your forearm, is often held off for several weeks, and the range may be limited at first. Has your shoulder dislocated before? Check with your physio first, and stop if it feels like it might slip out.

If you have had a hip replacement, get the go-ahead from your surgeon or physio before you try side-lying external rotation. Lying on your side lets the top leg slide forward or drop across the lower one, and many surgeons ask you to avoid that for the first months after some operations. A pillow between your knees helps keep the legs apart.

Written and checked by the PocketPhysio editorial team. Last updated 2026-09-28.

This page is general education, not a diagnosis or a personal treatment plan. If you have pain, an injury or a health condition, see a physiotherapist or doctor before starting new exercises.

Side-lying external rotation