The shoulder joint has the widest range of movement of any joint in your body. It is used to lift your arm, to reach above your head, to rotate and even to reach behind your back. The downside of this wide range of movement is that the shoulder is particularly vulnerable to injury. Once the head (ball) of the upper arm has been forced out of the shoulder socket, the shoulder can become unstable and prone to repeated dislocation and injury.
The shoulder joint comprises the shoulder blade, collarbone and upper arm bone (humerus). The labrum and ligaments of the shoulder capsule keep the head of the humerus in place in the shoulder socket (the glenoid). There are also strong muscles and tendons in and around the shoulder that enable the joint to move freely while keeping it stable.
When the shoulder becomes dislocated, the ball of the humerus may come fully or partially out of the socket, tearing the labrum, ligaments, muscles and tendons. Once they become loose or torn, these soft tissues may be less effective at keeping the joint in place. This is when recurrent instability can develop.
For some people a significant injury, or repeated dislocations can cause damage to the bone of the socket itself such that the ball ‘falls of’ the socket with the arm in certain positions.
Instability may also be due to repetitive strain, as the result of making repeated overhead movements (such as in swimming or tennis or in certain jobs like painting and decorating). However, some people are simply born with looser ligaments (hypermobility), which makes them prone to shoulder instability. People with hypermobility sometimes describe being ‘double-jointed’. The shoulder may feel loose or may dislocate in multiple directions, most common is forwards (anterior).
Symptoms of shoulder instability include:
- Repeated shoulder dislocations.
- A feeling of looseness or near dislocation in the shoulder joint with simple activities such as washing or getting dressed.
There are a number of methods that might be used to diagnose shoulder instability. Your doctor will carry out a detailed physical examination to assess the stability of your shoulder joint and test for looseness in the ligaments. You may be asked to make particular movements to assess the range of movement you have. You may also be referred for an X-ray, which will show any injuries to the bones, or an MRI arthrogram scan which will provide a detailed picture of the soft tissues, showing up problems with the labrum, ligament or tendons. This special type of MRI normally needs to be requested by a shoulder surgeon, as a standard plain MRI may fail to detect some of the injuries described above.
Depending on the extent of the instability in your shoulder, a number of treatments may be recommended. Normally, non-surgical treatment will be the first to be tried. Your doctor will recommend avoiding activities that cause pain and may suggest taking anti-inflammatories and painkilling medication. A physiotherapist may be able to recommend exercises to build strength and flexibility in your shoulder joint and improve stability. Exercises should be focussed on strengthening and balancing the rotator cuff muscles which can help keep the ball in the middle of the socket.
Dislocations and instability without injury (hypermobility) are much less likely to respond well to surgery, as people with this condition have loose ligaments surrounding the entire shoulder (and often other joints). Therefore in this condition physiotherapy is very important in the long term.
Dislocation from an injury leads to a 50% risk of developing further problems of instability, and a second dislocation is almost certain to lead to ongoing problems. These injuries often tear the labrum (cartilage) surrounding the joint. In these situations
then you may need to have surgery to repair the labrum to help improve your shoulder function. For this the main types of surgery is Arthroscopy. If here is significant damage to the bone then open surgery may be recommended.
- Arthroscopy – this is a minimally invasive technique (keyhole surgery) that uses a surgical instrument called an arthroscope which is inserted via a small incision in the skin. It contains a camera that allows the surgeon to see inside the shoulder joint. Tiny surgical instruments can be used to repair damage to the soft tissues (labrum) or tighten the shoulder capsule.
- Open surgery – this involves making a longer incision over the shoulder so the surgeon can access the joint and carry out any repairs that are needed. This is more likely when there is a significant bony damage to the socket (glenoid) or humeral head.
After both types of surgery you will need to wear a sling to keep your shoulder immobilised for between first two and six weeks. After this you will need to follow a programme of exercises to help you to rehabilitate and heal effectively and rebuild strength in your shoulder.