What is Shoulder Instability?
Shoulder instability occurs when the head of the upper arm bone is forced out of the shoulder socket. This can happen as a result of a sudden injury or from overuse. Once a shoulder has dislocated, it is vulnerable to repeat episodes. When the shoulder is loose and slips out of place repeatedly, it is called chronic shoulder instability.
Understanding your Shoulder Joint
Your shoulder is made up of three bones: your upper arm bone, your shoulder blade and your collarbone. The shoulder is a ball-and-socket joint: the ball, or head, of your upper arm bone fits into a shallow socket in your shoulder blade. Your shoulder also relies on strong tendons and muscles to keep your shoulder stable. Once the ligaments, tendons, and muscles around the shoulder become loose or torn, dislocations can occur repeatedly. Chronic shoulder instability is the persistent inability of these tissues to keep the arm centered in the shoulder socket.
- Labrum - The glenoid is ringed by strong fibrous cartilage called the labrum. The labrum forms a gasket around the socket, adds stability, and cushions the joint.
- Shoulder capsule - The joint is surrounded by bands of tissue called ligaments. They form a capsule that holds the joint together. The undersurface of the capsule is lined by a thin membrane called the synovium. It produces synovial fluid that lubricates the shoulder joint.
- Rotator cuff - Four tendons surround the shoulder capsule and help keep your arm bone centered in your shoulder socket. This thick tendon material is called the rotator cuff. The cuff covers the head of the humerus and attaches it to your shoulder blade.
- Bursa - There is a lubricating sac called a bursa between the rotator cuff and the bone on top of your shoulder (acromion). The bursa helps the rotator cuff tendons glide smoothly when you move your arm
Types of Shoulder Instability
- Subluxation - The ball of the upper arm comes just partially out of the socket. This is called a subluxation.
- Complete - The ball comes all the way out of the socket.
What is the cause of Shoulder Instability?
There are three common ways that a shoulder can become unstable:
- Shoulder Dislocation - Severe injury, or trauma, is often the cause of an initial shoulder dislocation. When the head of the humerus dislocates, the socket bone (glenoid) and the ligaments in the front of the shoulder are often injured. The labrum — the cartilage rim around the edge of the glenoid — may also tear. This is commonly called a Bankart lesion. A severe first dislocation can lead to continued dislocations, giving out, or a feeling of instability.
- Repetitive Strain - Some people have loose ligaments in their shoulders. This increased looseness is sometimes just their normal anatomy. Sometimes, it is the result of repetitive overhead motion such as swimming, tennis, and volleyball. Looser ligaments can make it hard to maintain shoulder stability. Repetitive or stressful activities can challenge a weakened shoulder. This can result in a painful, unstable shoulder.
- Multidirectional Instability - In a small minority of patients, the shoulder can become unstable without a history of injury or repetitive strain. In such patients, the shoulder may feel loose or dislocate in multiple directions, meaning the ball may dislocate out the front, out the back, or out the bottom of the shoulder. This is called multidirectional instabilit
What are the symptoms of Shoulder Instability?
Common symptoms of chronic shoulder instability include:
- Repeated shoulder dislocations/Repeated instances of the shoulder giving out
- A persistent sensation of the shoulder feeling loose, slipping in and out of the joint, or just "hanging there"
- X-rays - These pictures will show any injuries to the bones that make up your shoulder joint.
- Magnetic resonance imaging (MRI) - This provides detailed images of soft tissues. It may help your doctor identify injuries to the ligaments and tendons surrounding your shoulder joint.
Chronic shoulder instability is often first treated with nonsurgical options. If these options do not relieve the pain and instability, surgery may be needed.
Your doctor will develop a treatment plan to relieve your symptoms. It often takes several months of nonsurgical treatment before you can tell how well it is working. Nonsurgical treatment typically includes:
- Activity modification - You must make some changes in your lifestyle and avoid activities that aggravate your symptoms.
- Medication - You will be prescribed medications which will reduce pain and swelling.
- Physiotherapy - Strengthening shoulder muscles and working on shoulder control can increase stability.
Surgery is often necessary to repair torn or stretched ligaments so that they are better able to hold the shoulder joint in place.
- Arthroscopy - Soft tissues in the shoulder can be repaired using tiny instruments and small incisions. This is a same-day or outpatient procedure. Arthroscopy is a minimally invasive surgery. Your surgeon will look inside the shoulder with a tiny camera and perform the surgery with special pencil-thin instruments.
- Open Surgery - Some patients may need an open surgical procedure. This involves making a larger incision over the shoulder and performing the repair under direct visualization.
After surgery, your shoulder may be immobilized temporarily with a sling. When the sling is removed, exercises to rehabilitate the ligaments will be started. These will improve the range of motion in your shoulder and prevent scarring as the ligaments heal. Exercises to strengthen your shoulder will gradually be added to your rehabilitation plan. Your commitment to physiotherapy is the most important factor in returning to all the activities you enjoy.