Summary

Some of the common causes of shoulder pain are discussed below.

1. Shoulder dislocation
   It can happen when playing sports or in people who are hypermobile when the shoulder is pulled back too hard or rotated too far. This results in your arm bone popping out of the socket. You will feel pain accompanied with weakness in your shoulder along with bruising, swelling and occasionally numbness.
2. Collar bone separation
   Your collar bone (clavicle) and your shoulder blade (scapula) make a joint known as acromioclavicular joint. A direct blow to this joint or a fall can tear the ligament which is holding these bones together. It may result in your collar bone being pushed out of place. Clinically, you will experience pain, bruising, pain especially to the overhead movements of the arm along with a bump on top of your shoulder.
3. Fracture
   Fractures are broken bones which can involve your collar bone, your upper arm bone (humerus) or your shoulder blade (Scapula).

   This happens during sports, especially contact sports, motorbike accident or sometimes a fall from a standing height. This will cause pain, bruising, swelling and restricted and painful movements. If your collar bone is broken you may notice a bump, your shoulder can sag. Again, you will have bruising and  pain along with reduced movements.

4. Bursitis
   Bursa is a fluid filled sac that cushions your shoulder joint. Bursa can get irritable and swollen during a fall or if you repeat the same motions over and over again. This will result in pain especially to the overhead movements.
5. Impingment
   Shoulder impingement is essentially a pressure on the underlying tendon which gets squashed between the top of your arm bone ( humerus ) and top of the shoulder blade ( acromion ) especially on overhead movements. The acromion will rub or impinge on the rotator cuff tendons and on to the bursa which will then irritate the bursa and cause swelling which will in turn cause pain especially on overhead movements along with limited range of motion.
6. Rotator cuff tendon tear
   You have four rotator cuff tendons inside your shoulder joint. They can tear as a result of acute injury for example playing sports or as we grow old secondary to degenerative changes. It can also happen because of long term wear and tear or repetitive use. This can then irritate the overlying bursa which can result in pain, restricted movements and weakness to your shoulder.

   Tear to these rotator cuff tendons can be partial or may be complete. In a complete tear the tendon is pulled away from the attachment to the bone. Most common rotator cuff tendon to be involved is the supraspinatus muscle / tendon followed by biceps tendon injuries.

7. Osteoarthritis
   Like the knee and a hip arthritis, osteoarthritis can also involve the shoulder joint. It is also known as a degenerative joint disease which happens because of wear and tear. Essentially the cartilage (Cushion) between the upper arm bone and the socket wears off and then the two bare bones rub on each other. This results in stiffness, pain and reduced movements.
8. Frozen shoulder (Adhesive Capsulitis)
   In this condition your joint movement reduces drastically. Essentially scar tissue (adhesions) build up in the joint which prevents your shoulder from moving freely. This can happen after an injury, after an operation or it can happen in diabetics. Patients with this condition will experience pain, and limited movements. It can resolve in time if it is mild or it may need medical attention and treatment.
9. Instability
   Shoulder instability occurs when the head of the upper arm bone is forced out of the shoulder socket. It can happen by a direct blow to the shoulder or in patients with epilepsy. The shoulder can come partially out of socket or it can completely come out in which case it will need medical attention.It can be a recurring problem in patients who are hypermobile.

   Repeated episodes of subluxations or dislocations can increase the risk of developing arthritis in the joint. You will need medical attention to assess muscles and ligaments around the joint and may then need physiotherapy or in some cases surgery.

When you see your doctor, they will take a medical history followed by a physical examination to your shoulder joint. The doctor may then order tests like x-rays, MRI scan, ultrasound scan or a CT scan to assess bones, rotator cuff tendons, ligaments etc.

Once he has made a diagnosis, he will then make a treatment plan for you. Treatment generally will involve rest, analgesia, physiotherapy, modifications to your daily activities. A large proportion of patients will respond to non-operative treatment. However, certain shoulder problems like recurring subluxations or dislocations, some rotator cuff tears, some fractures, AC joint separation etc. may need surgery.

The doctor may also try injecting a corticosteroid injection (an anti-inflammatory medicine) into the shoulder joint to relieve joint swelling and pain.

Surgery can involve arthroscopy (keyhole operation) to remove the scar tissue or repair the torn tendons or traditional open procedures for fractures, larger reconstructions or shoulder replacement.

You will then be seen by a physiotherapist to help you strengthen and stretch your muscles and tendons and to improve the range of your motion.