dislocation
Meaning of dislocation: A joint that has come apart and stayed apart, which is a different problem from one that slipped and went back.
Definition of dislocation
A dislocation is an injury in which the bone surfaces forming a joint are pushed completely out of contact and remain out of position. The joint looks misshapen, cannot be moved normally, and is usually very painful. Ligaments and the capsule surrounding the joint are torn or stretched in the process, and a fragment of bone is sometimes chipped off at the same time.
How is it different from a subluxation?
By whether the surfaces keep any contact. In a subluxation the bone ends slip out of alignment but still overlap, and they frequently return to position on their own, leaving pain and a sense of the joint having given way. In a dislocation the surfaces separate completely and stay separated until they are put back. The distinction matters because the tissues holding the joint together are torn more extensively in the second, and because a joint locked out of position blocks movement outright.
| Term | What has happened |
|---|---|
| Dislocation | Surfaces fully out of contact and staying out |
| Subluxation | Partly out of position, often slipping back unaided |
| Fracture-dislocation | The joint is out and a bone forming it is broken |
| Separation | The joint at the outer end of the collarbone is disrupted |
| Developmental dislocation | The joint formed out of position rather than being forced out |
Why is a separated shoulder not a dislocated shoulder?
They involve different joints carrying similar names. A dislocated shoulder means the ball of the upper arm bone has left its shallow socket on the scapula, the shoulder blade. A separated shoulder means the small joint at the outer end of the clavicle, where the collarbone meets a bony shelf of the shoulder blade, has been disrupted by its ligaments tearing. Both follow a fall onto the shoulder and both hurt across the same region, and the everyday names invite the mix-up.
What happens to the joint afterward?
The torn capsule and ligaments heal, but often longer and looser than before, and the rim of cartilage deepening a socket may have been stripped away in the process. A joint that has dislocated once is therefore more likely to dislocate again, and that tendency is strongest in young people whose first shoulder dislocation followed a substantial force. Nerves and vessels running close to a displaced joint can be stretched or compressed while it sits out of position, so sensation and circulation beyond the joint are assessed alongside the joint itself.
Also known as
Used in a sentence
The dislocation was reduced under sedation and the joint immobilized afterward.
Good to know
A separated shoulder involves the joint at the outer end of the collarbone while a dislocated shoulder involves the ball leaving its socket, so the two everyday names describe different injuries.
Word origin
Where “dislocation” comes from
From the medieval Latin dislocare, to put out of place, built from dis-, meaning apart, and locus, a place.