There can be many reasons for shoulder pain some of the most common are explained.
Shoulder Pain Causes
1. Tendinitis – Tendons are strong fibres that attach muscles to bones. Tendinitis is inflammation of a tendon and commonly affects shoulders. Tendons are quite often affected by repetitive motions. Switch up your transitions in yoga and try to use the muscles within the joints evenly. Many of the rotator cuff muscles can be affected by tendinitis one of the most commonly affected is the supraspinatus tendon. Occasionally a calcium deposit may form in the rotator cuff and cause acute inflammation of the tendon and bursa. This is called calcific tendinitis.
2. Bursitis – If the space between the rotator cuff and the bone above it is reduced, the rotator cuff tendons and the overlying bursa can become subjected to pressure leading to bursitis and tendinitis. (anterosuperior impingement syndrome, common in yoga, is classified as impingement in the under surface of the anterior third of the acromion).
3. Muscle injury – Usually a rotator cuff tear which is 1 of 4 muscles that surround and act on the shoulder.
4. Instability – The glenohumeral joint is a ball-and-socket joint. The motion that the glenohumeral joint provides is flexion, extension, abduction and adduction. Glenohumeral instability is the inability to maintain the humeral head into the socket (glenoid fossa).
5. Arthritis – The shoulder can be affected by many forms of arthritis. Osteoarthritis, rheumatoid arthritis, and traumatic arthritis are the most common types affecting the shoulder.
6. Anterior dislocation often occurs when the anterior ligaments are overstretched or previously damaged and the arm is abducted and externally rotated.
Shoulder Muscles & Ligaments
Here is a complete list of muscles and ligaments.