Before looking at what direction the shoulder most commonly dislocates let’s have a look at the physical make-up (anatomy) of the shoulder.
The shoulder allows the human body the biggest range of multi-axial movement of any other joint in the human body. It is made up of 30 muscles, 4 major bones, 6 ligaments and tendons which are linked and work together to give us that flexibility in movement.
The shoulder joint can be simply explained as a ball and socket joint where the top of the humerus (upper arm) bone (which has a ball-like head) fits into the scapula (shoulder blade). The range of movement and flexibility afforded to this joint comes from the complex interaction between the related muscles, ligaments and joints.
Precisely because of the unique anatomy of the shoulder joint it is more susceptible to dislocation, unlike the hip joint which has a deeper socket. Shoulder dislocation is often seen in contact sports such as football, rugby or any sports-related accident. In fact, shoulder dislocation happens with blunt force, a fall or impact to the front or rear of the shoulder, the type most commonly seen with sports injuries such as during football play, hockey or a rugby tackle. Other sports where the player commonly falls, have a high incidence of shoulder dislocation too, such sports as gymnastics and volleyball (when the players dive to the ground).
What Happens When the Shoulder Joint Dislocates?
Dislocation of the shoulder is when the arm bone (the ball part of the joint) is forced out of the socket in which it is held. The most common direction for the shoulder to dislocate is to the front of the shoulder, but let’s take a look at all the possibilities:
- Anterior dislocation – is where the dislocation is at the front of the shoulder and is the most common type of shoulder dislocation occurring in 90% of cases. It is brought on my a blunt impact or fall. The humerus head is forced out of the socket anteriorly, causing tears with fractures sometimes occurring on the humeral head or other parts of the bone.
- Posterior dislocation is where the dislocation is at the rear side of the shoulder. Posterior dislocation is less common accounting for about 10% of shoulder dislocations and is much harder to detect (or see) and patients may come to seek treatment having had the dislocation for a prolonged period of time. This type of dislocation is caused by a fall onto a forward flexed arm. Symptoms, unlike an anterior dislocation, can be minimal resulting in missed diagnosis.
- Inferior dislocation – an injury not seen very often, where a blunt force causes impingement of the neck of the humerus , pushing the humeral head out inferiorly. The pain associated with this type of dislocation is acute and the humeral head can be felt on the lateral chest wall.
- Partial dislocation – or subluxation – happens when the ball of the arm bone comes partially out of the socket, the difference between subluxation and dislocation is that in a dislocation the entire head of the humerus is forced out of the socket in which it is held. This type of injury is as serious as a dislocation and should be considered as serious as a “full” dislocation.
What To Do in the Case of Shoulder Dislocation
If there is no possibility of immediate medical assistance, you should get to your nearest A&E department as quickly as possible. You should not try in any way to pop your arm by yourself as this could cause more tissue damage. Limit movement of the arm as much as possible.
Upon arrival at A&E an x-ray will usually be carried out to assess further damage such as fractures or broken bones. If there are no breaks present, a procedure known as “reduction” where the dislocated bone is gently moved back into its place. Pain killers will be administered sometimes along with sedatives to help alleviate stress and pain.