Treating Shoulder Pain with Acupuncture (1)
Basic shoulder anatomy:
Bones and joints of the shoulder:
- The shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone).
- Two joints facilitate shoulder movement- The acromioclavicular (AC) joint, and the glenohumeral joint.
- The AC joint is located between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle.
- The glenohumeral joint, to which the term “shoulder joint” commonly refers, is a ball-and-socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body. The “ball” is the top, rounded portion of the upper arm bone or humerus, while the “socket” or glenoid, is the dish-shaped part of the outer edge of the scapula into which the ball fits.
- The shoulder joint is prone to injury because the ball of the upper arm is larger than the shoulder socket that holds it. To remain stable, the shoulder must be anchored by its muscles, tendons, and ligaments.
Soft tissue structures of the shoulder:
- The soft tissues of the shoulder include several muscles, the tendons and ligaments that hold the joints in place, two fluid-filled sacks called bursae, and the glenohumeral joint capsule.
Over a dozen major muscles as well as several minor muscles act on the shoulder joint, allowing the arm to flex, extend and rotate to position the forearm and hand exactly where we wish it to be.
- The tendons of four of these muscles form the rotator cuff, which holds the ball at the top of the humerus into the glenoid cavity (the dish-shaped part of the scapula) and provides mobility and strength to the shoulder joint.
- Several ligaments stabilise the shoulder even further.
- Tendons are tough cords of tissue that attach muscles to bone.
- Ligaments attach bones to bone, providing stability.
- The shoulder contains two bursae (flimsy sac-like structures) that cushion and protect the rotator cuff from the bony arch of the acromion, allowing for the smooth gliding between bones, muscles, and tendons. (‘Bursitis’ is inflammation of these bursa).
- The glenohumeral joint capsule is a soft tissue envelope that encircles the glenohumeral joint and attaches to the scapula, humerus and the head of the biceps muscle. It is lined by a thin, smooth synovial membrane which houses synovial fluid- the lubricating fluid of the joint.
- It is this capsule that becomes inflamed, thickened and stiff in ‘frozen shoulder’.