Joint dislocation

In a joint, the ends of the bones fit together, with the surrounding joint capsule, ligaments, and muscles holding them in place. When a sudden external force exceeds what this fit can withstand, the ends of the bones move out of position. Typical situations include landing on your hand during a fall, colliding with another player during sports, or sustaining a major impact in a traffic accident.

Some joints dislocate more easily than others. A joint with a shallow socket that allows a large range of movement, such as the shoulder, dislocates relatively easily, while a deeply fitted joint such as the hip usually dislocates in a major accident. Once a joint has dislocated, its capsule and ligaments are stretched, making it more likely to dislocate again. For details about individual joints, see Shoulder dislocation and subluxation, Hip dislocation, Knee dislocation, Patellar dislocation and subluxation, and Temporomandibular joint dislocation.

• Dislocation: The joint surfaces are completely displaced, to the point that they no longer touch each other.
• Subluxation: The joint surfaces are partly displaced. This also includes cases in which they slip out and then return to their normal position on their own.

These are different from both sprains and fractures. A sprain is a stretched or torn ligament, while a fracture is a broken bone. When a dislocation occurs together with a fracture, it is called a Fracture-dislocation. The feeling that a joint is repeatedly unstable is covered separately in Joint instability.

“Subluxation” can be confusing because it has different meanings depending on the context.

• Subluxation in medicine and rehabilitation: This means partial displacement of the joint surfaces. This is the meaning described above.
• Subluxation in chiropractic: This is the concept that a slight misalignment of a vertebra affects nerve function. Its usage differs from the partial displacement of joint surfaces described in orthopedics. For details, see Chiropractic vertebral subluxation.

Books describing Integrative Manual Therapy explain shoulder subluxation in terms of the pull of muscles. They propose that when the subscapularis at the front of the shoulder goes into spasm, the humeral head is pushed forward and becomes more prone to displacement, and that a spasm of the latissimus dorsi pulls the humeral head downward, causing inferior subluxation. The book presents the latissimus dorsi as the more important cause at the shoulder joint of these two muscles. This approach therefore looks not only at the joint itself, but also at the balance of tension in the muscles pulling on it.

Shoulder subluxation in which one arm droops after a stroke is viewed from the same perspective. The explanation is that when the force pulling the arm backward and downward becomes dominant, the humeral head drops below its position in the joint. This discussion continues in Hemiplegic shoulder.

At the hospital, clinicians first use X-rays or other imaging to check for an accompanying fracture, then return the joint to its normal position. This is called reduction. A period of protection for the joint follows, then rehabilitation to restore restricted movement and muscle strength. The duration and methods vary considerably depending on which joint dislocated, how it dislocated, and whether ligaments or bones were also injured. If the same joint has dislocated two or more times, discuss ways to prevent recurrence with your medical team.

• Do not try to put the joint back yourself. Forceful pulling can injure nerves, blood vessels, and nearby bones. It is safer not to follow methods found online.
• Support it to keep it from moving. Support it in the most comfortable position with a towel or triangular bandage, and go to the hospital. Applying an ice pack wrapped in cloth can help reduce swelling and pain.
• Check swelling, color, and sensation. If your fingertips or toes are cold and pale, tingling, or have no sensation, go to the emergency department immediately. These may be signs that a blood vessel or nerve is being compressed.
• Wait for approval from your medical team before receiving massage or hands-on treatment. The area around a previously dislocated joint remains weakened for a while. Before receiving treatment, tell the practitioner that the joint has dislocated before.