Your shoulder has the greatest range of motion of all your joints. This makes it susceptible to injury, as well as arthritis. Symptoms vary depending on the cause.

A shoulder injury may cause:

• Sudden, sharp pain
• Swelling
• Spasms in shoulder muscles
• Weakness in arm or shoulder
• Inability to move shoulder
• Tingling or numbness

Shoulder arthritis may cause:

• Gradual pain
• Shoulder stiffness
• Shoulder or arm weakness
• Difficulty moving shoulder

Risk factors include:

• Overhead activities like painting a ceiling or cleaning a cupboard can trigger pain, particularly in people who already have arthritis.
• High-impact, high-speed sports like football, rugby and skiing are often responsible for rotator cuff tears and shoulder separations.
• Tennis, swimming and baseball can all cause overuse injuries.

Causes include:

• Arthritis – Osteoarthritis occurs when cartilage in your shoulder joint gradually wears away with age and use. Other types of arthritis can occur following a shoulder injury or infection.
• Bursitis – Swelling in the fluid-filled sacs that cushion spaces around the bones of your shoulder joint, acting like shock absorbers.
• Fracture – Older people who fall are susceptible to fractures in the bones of the shoulder. Younger people are more likely to fracture their shoulder in a car accident or while playing contact sports.
• Dislocated shoulder – Dislocation occurs when the upper arm bone is forced out of the shoulder socket, usually by a sudden injury.
• Rotator cuff injury – Injury to the muscles and tendons around the shoulder joint are more common in laborers or those whose jobs require then to work with their arms lifted overhead. The risk increases with age.
• Tendinitis or tendon tear – Inflammation or tears in the tendon – tissue that connects muscle to bone – can occur during work or sports that involve overhead activities like throwing or hitting a ball or more commonly from a ground level fall.

Your doctor will ask questions to get your medical history, and do a physical exam to check for mobility, swelling, weakness or tenderness.

Your doctor may also recommend other tests, including:

• X-ray – X-rays use electromagnetic waves to take pictures of the bones in your shoulder. They can show fractures and damage to bones.
• MRI – Magnetic resonance imaging uses a powerful magnet and radio waves to create cross-sectional of tissue around your shoulder. MRIs help find tears to tendons, ligaments, muscles and cartilage.
• CT scan – Computed tomography combines x-rays with computer technology to make detailed, cross-sectional and 3D images of the bones in your shoulder.
• Electrical studies – Tests such as EMG (electromyogram) can evaluate nerve function.
• Arthroscopy – This minimally invasive procedure inserts a tiny, lighted tube into the shoulder joint. Pictures from inside the joint are projected onto a screen, helping doctors to spot and treat arthritic changes and tendon and ligament tears. 

Treatment depends on the cause of your shoulder pain.

• Rest and ice – Mild shoulder pain can sometimes be treated at home. Apply ice wrapped in a towel for 15 minutes once an hour. Rest and avoid activities that cause shoulder pain.
• Medications – Anti-inflammatory medicine such as ibuprofen (Motrin/Advil) or naproxen (Aleve) can help ease swelling. Acetaminophen (Tylenol) can help relieve pain.
• Physical therapy – Physical therapy can help you learn safe and effective exercises to improve your shoulder strength and mobility.
• Injections – Corticosteroid shots may help reduce inflammation and pain for a few months.
• Arthroscopic surgery – Long, narrow tools fitted with a tiny camera are inserted into your shoulder joint. Using these tools, surgeons can reconstruct torn tendons, repair damaged cartilage and remove inflamed tissue or loose cartilage. 
• Shoulder replacement surgery – The surgeon replaces damaged bone and cartilage in your shoulder with an artificial joint made of metal alloys and medical grade polyethylene (plastic). Most shoulder replacements last longer than 10-15 years.