Dislocation is the total displacement of the articular end of a bone from the joint cavity. Incomplete displacement is called subluxation.  Reduction means restoration of the normal alignment of the bones.

        Classification: Dislocations are classified as follows:

                    a) Congential
                    b) Traumatic
                    c) Pathological
                    d) Paralytic

        Congential dislocation are dealt with in congential deformities

TRAUMATIC DISLOCATION

        This usually follows a serious violence. The following are the clinical types of dislocation.

                i) Acute dislocation
                ii) Old unreduced dislocation
                iii) Recurrent dislocation
 
i) Acute dislocation

        The traumatic dislocation commonly occur in the shoulder, elbow and hip. The acute dislocation are further classified according to the direction of dislocation of the distal bone in relation to the proximal e.g. Anterior, posterior etc. Clinically the acute traumatic dislocation is diagnosed by the history and the findings. There is acute pain and swelling around the joint. There is gross deformity at the joint, and the bony landmarks are distorted. The clinical sings common to all dislocation fall into 2 groups.

        1.  The sings denoting the absence of the articular end of a bone from its normal anatomical
            position.

        2. Sings denoting the presence of the displaced end of the bone in an abnormal position.

        One should look for associated nerve and vascular injuries. Radiographs confirm the
diagnosis and detect associated fractures.

        Management: Acute dislocation of a joint is an orthopaedic emergency and it requires immediate reduction under anaesthesia. After reduction the part should be immobilised till the soft tissues like the capsule and ligaments heal. After about 3-4 weeks the joint is mobilised by exercise therapy.

ii) Old unreduced dislocation

        Patients with unreduced dislocation present themselves for treatment weeks to months after the primary dislocation. This is unfortunately common in India due to unsuccessful treatment by indigenous practitioners carried out in rural  areas. These are difficult problems and need prolonged treatment

        Treatment: Closed reduction under anaesthesia is attempted in cases presenting within four weeks. This should not be done in dislocations more than six to eight weeks old as there is danger of fracture during the manipulation. Surgical reduction is indicated in such cases.

iii) Recurrennt Dislocation

        When a traumatic dislocation of a joint is followed by subsequent frequent dislocations by minimal trauma, it is called recurrent dislocation. This is particularly common in the shoulder joint and patello femoral joint.

PATHOLOGICAL DISLOCATION

        This is caused by some disease process and is common in the hip joint. This occur when there is destruction of the head of the femur or excessive distention of the joint capsule.

Destructive Dislocation

        This is common in the following condition: (I) Tuberculosis of the hip when there is a travelling acetabulum, (ii) Septic arthritis of the hip of infancy where there is total destruction of the head of femur.

Distensive Dislocation

        The head of the femur gets dislocated when the joint capsule is rapidly distended by an effusion of synovial fluid or pus.

PARALYTIC DISLOCATION

        This occurs when there is marked imabalance of muscle power. It can occur in the hip whenever there is an overaction of the hip flexors and adductors, in certain paralytic conditions. This is always a posterior dislocation. In poliomyelitis, when the hip extensors and abductors are paralysed, the normal adductors and flexors overact and cause dislocation. In cerebral palsy, the spasm of the adductors and flexors cause the dislocation.