The major difference between a Medical Subluxation and Chiropractic Subluxation is actually quite massive, not only by definition but by the treatment as well. Medical subluxation deals with a dislocation or displacement of the joint. One of the most common dislocations is seen in the shoulder. When a medical dislocation occurs there is often intense pain, swelling, as well as disruption of the two surfaces of the joint as well as to the soft tissue structures (such as the muscles and especially the ligaments). The primary goals of this dislocation is to rest it (usually immobilization) and then when the patient is out of pain, begin the process to stabilize the injury. Essentially, this is where rehabilitation and strengthening the joint come into play.
On the other hand, we have a Chiropractic Subluxation. While there are different words for this, the basic premise is that a Chiropractic Subluxation is a spinal segment that is has a reduced range of motion. This in turn can alter joint biomechanics, physiology, and can cause the body to have neural lesions (decreased neural stimulation). The decrease in motion can cause the body to compensate while the decreased neural activity can place pressure on a the nervous system which leads to dysfunction and Ill-health as the nerves that leave the spine also go to the muscles and organ systems. The way Chiropractors go about treating this is by applying a controlled force to help move the joint into a correct position.