Rotator cuff injury: The rotator cuff is a group of muscles and tendons that surround the shoulder joint. Injury or strain to the rotator cuff, such as a tear or tendinitis, can cause shoulder pain, weakness, and limited range of motion.

Shoulder impingement: Shoulder impingement occurs when the tendons of the rotator cuff become compressed or pinched between the bones of the shoulder, particularly the acromion. This can cause pain, inflammation, and difficulty raising the arm.

Frozen shoulder: Also known as adhesive capsulitis, frozen shoulder is a condition characterized by stiffness and pain in the shoulder joint. It occurs when the connective tissue surrounding the joint becomes thickened and tight.

Shoulder dislocation: A shoulder dislocation happens when the upper arm bone (humerus) pops out of the shoulder socket. This can cause sudden and severe pain, along with swelling and instability in the shoulder.

Shoulder arthritis: Arthritis can affect the shoulder joint, causing pain, stiffness, and reduced range of motion. Osteoarthritis and rheumatoid arthritis are the most common forms of arthritis that can affect the shoulder.

Bursitis: Bursitis is inflammation of the fluid-filled sacs (bursae) that cushion and lubricate the joints. Inflammation of the bursae in the shoulder can result in pain and limited shoulder mobility.

Tendinitis: Tendinitis is inflammation or irritation of the tendons in the shoulder, often caused by overuse, repetitive motions, or sudden excessive force. It can lead to pain and difficulty with shoulder movements.

Shoulder instability: Shoulder instability occurs when the shoulder joint is loose and prone to partial or complete dislocation. It can cause pain, weakness, and a feeling of the shoulder "slipping out" of place.

Shoulder fractures or injuries: Fractures or injuries to the bones, ligaments, or cartilage in the shoulder can cause pain, swelling, and limited mobility. These injuries may result from accidents, falls, or sports-related trauma.

Other causes: Other factors that can contribute to shoulder pain include muscle strains, nerve impingement, referred pain from the neck or upper back, certain systemic conditions, or even heart-related conditions (though less common).