Shoulder

The word “shoulder” can refer to different places depending on who uses it. It may mean the joint where the arm connects to the trunk, or the area along the upper trapezius, running from the neck to the tip of the shoulder, that tends to feel tight. The area people commonly describe as having “knots in the shoulders” is anatomically closer to the neck and back, so information about the shoulder often overlaps with the Neck article.

The shoulder joint consists of the round head of the humerus resting in a shallow, dish-like socket. It is often compared to a golf ball sitting on a tee. This allows large movements forward and backward, from side to side, and in rotation, but the surrounding soft tissues provide most of the joint's stability.

• Four joints — The glenohumeral joint between the humerus and scapula, the acromioclavicular joint where the tip of the scapula meets the clavicle, the joint between the clavicle and sternum, and the scapulothoracic articulation, where the scapula glides over the rib cage, all work as a team.
• Rotator cuff — The supraspinatus muscle, infraspinatus muscle, teres minor, and subscapularis surround the humeral head to keep it centered in the joint and also rotate the arm.
• Deltoid muscle — This large muscle forms the rounded contour of the shoulder and is the most noticeable muscle when you raise your arm.
• Muscles around the scapula — The levator scapulae, trapezius, rhomboids, and serratus anterior position and move the scapula appropriately.
• Labrum and ligaments — The labrum deepens the rim of the socket, while the ligaments help keep the joint from slipping out of place.

When you raise your arm, the humerus and scapula move together at a ratio of approximately 2:1. This coordination is called scapulohumeral rhythm. As you lift your arm overhead, the scapula rotates along with it, allowing the arm to rise higher.

The shoulder is constantly used, not just during vigorous exercise but also in small everyday movements. Almost every daily activity involves it: taking something off a shelf, washing your hair, getting dressed, reaching behind your back, or carrying a bag. Shoulder discomfort can therefore become noticeable at unexpected moments. Your arm may catch while getting dressed, pressure on your shoulder may wake you when you lie on your side, or just one shoulder may feel heavy.

Carrying a bag on one side or sitting in the same position for a long time can make the shoulders prone to rounding and aching across the top. On the other hand, not using the shoulder can make its range of motion feel reduced. The shoulder is a joint whose movement reflects how it is doing. Changes seen on imaging do not always match the pain you actually feel, so considering the location and nature of the discomfort alongside movement and daily habits can help guide your understanding.

• Avoid staying in one position for too long. While at your desk, make large backward shoulder circles every hour.
• Distribute your load. Alternate the side on which you carry your bag, and avoid leaving it on one shoulder for a long time.
• Let the scapula move along as you raise your arm. When lifting your arm, try moving with a sense of gently lowering the scapula rather than shrugging the shoulder upward.
• Open the front of your chest. A stretch with your arms against a doorframe and your chest moving forward can help rounded shoulders.
• Move your upper back. Good thoracic mobility is needed to raise the shoulder high.
• Check your sleeping setup. When sleeping on your side, hug a pillow to support your arm. See Shoulder compression during side sleeping for ways to do this.

Find by pain location — Anterior shoulder pain below · Posterior shoulder pain below · Shoulder compression during side sleeping

Find by sensation or pattern — Shoulder mobility · Shoulder instability · Shoulder dislocation and subluxation · Shoulder asymmetry

Commonly discussed conditions — Adhesive capsulitis · Shoulder impingement syndrome · Rotator cuff disorders · Rotator cuff tear · Glenoid labral tear · Acromioclavicular joint separation · Suprascapular nerve entrapment · Levator scapulae syndrome

Posture and alignment — Rounded shoulders · Scapular winging · Scapular dyskinesis · Crossbody bag

Work and daily-life strain — Wrist and shoulder strain in webtoon artists and illustrators · Neck and shoulder strain during breastfeeding · Chest breathing and neck and shoulder tension

Exercise and sports — Swimmer's shoulder · Glenohumeral internal rotation deficit · Archery injuries · Baseball pitching biomechanics

Associated structures — Subclavian artery · Axillary artery · Axillary nerve · Brachial plexus · Shoulder abduction relief test

Anterior shoulder pain refers to discomfort in the area extending from the outer end of the clavicle to the front of the humerus. Several structures overlap beneath any one spot, so pain in the same location can have different causes in different people.

Several structures pass through this area.

• Long head tendon of the biceps brachii — It travels upward along a groove on the front of the humerus, enters the shoulder joint, and attaches to the upper part of the labrum. Because this groove lies just beneath the skin, it is the spot most often identified as painful when pressed (Biceps tendinitis).
• Space beneath the acromion — This contains the supraspinatus muscle tendon and a bursa. There is a growing tendency to describe what was previously called shoulder impingement syndrome as “subacromial pain syndrome,” a term that does not attribute it to a single cause.
• Acromioclavicular joint — This is the small joint at the outer end of the clavicle.
• Upper labrum — Terms such as SLAP lesion refer to the area where the biceps brachii attaches.
• Front of the deltoid muscle — This muscle can ache if you frequently lift your arm forward.
• Pain referred from the neck — Radicular pain or referred pain may be felt at the front of the shoulder.

So, rather than immediately suspecting a single structure when the front of the shoulder hurts, it helps to consider the direction and height at which raising the arm causes pain, as well as how it feels when lying down at night or getting dressed. Rotator cuff changes on imaging are common even in people without pain (Asymptomatic imaging findings), so clinicians assess imaging results together with symptoms and movement.

Posterior shoulder pain refers to discomfort in the area extending from the outer edge of the scapula to the back of the humerus. It forms a counterpart to anterior shoulder pain, but differs in that the scapula and its surrounding muscles are involved together, rather than just the shoulder joint.

• Posterior rotator cuff — The infraspinatus muscle and teres minor originate on the back of the scapula and attach to the back of the greater tubercle of the humerus, rotating the arm outward.
• Posterior joint capsule — This is the back portion of the sac surrounding the shoulder joint. Stiffness here can reduce the range through which the arm rotates inward. A typical example is glenohumeral internal rotation deficit, which is often discussed in people who repeatedly perform throwing movements.
• Muscles around the scapula — The rhomboid muscles, levator scapulae, middle and lower trapezius, teres major, and upper part of the latissimus dorsi span this area.
• Pain referred from the neck — Radicular or referred pain originating in the cervical spine is also commonly felt behind the shoulder or between the scapulae.

Some people are particularly interested in how the scapula moves. Scapulohumeral rhythm, in which the humerus and scapula move together as the arm is raised, is a well-established observation. Differences in scapular movement (scapular dyskinesis) are also commonly observed in people without shoulder pain. Rather than drawing conclusions about pain from scapular shape or movement alone, it is helpful to consider actual use, fatigue, and posture as well.