Physical Therapy in San Jose, Los Gatos, Foster City and Burlingame for Shoulder
Q: If my shoulder popped out of the socket but went back in the socket by itself, do I have a subluxation or a dislocation?
A: Subluxation is usually defined as an incomplete instability event that did not require manual assistance to reduce it. Manual assistance refers to a doctor or emergency medical technician using a hands-on technique (or surgery) to put the joint back in place. A shoulder that pops out of the joint but goes back in on its own is technically still a subluxation.
Dislocation is a complete disruption of the joint that requires some means of relocation (either the manual technique or surgery). The joint was forced out of the socket and didn't go back in without help.
But there is technically a third classification that falls somewhere in-between. Orthopedic surgeons from West Point have proposed using the term transient luxation. Transient means temporary. Luxation refers to a separation of the two joint surfaces with enough force to cause damage to the joint or surrounding tissue.
They came up with this idea after investigating the kind of damage that occurs within the joint of first-time (acute) shoulder subluxations. Because these injuries normally spontaneously reduce (head of the humerus goes back into the socket by itself), X-rays and MRIs aren't routinely taken. But in this study, they were able to look at imaging studies taken within two weeks of the initial injury and see significant changes.
Most had both a Bankart and a Hill-Sachs lesion. A Bankart lesion indicates damage to the cartilage around the rim of the shoulder socket. The Hill-Sachs lesion appears as a dent in the bone of the head of the humerus (round ball at the top of the upper arm bone). It's an indication that the head of the humerus hit the edge of the socket on its way out of (or back in) the socket.
What you describe sounds like a subluxation but more specifically, you may have had a transient luxation.
Reference: Lieutenant Colonel Brett D.Owens, MD, et al. Pathoanatomy of First-Time, Traumatic, Anterior Glenohumeral Subluxation Events. In The Journal of Bone and Joint Surgery. July 2010. Vol. 92-A. No. 7. Pp. 1605-1611.