Robin McKenzie (b.1931- d.2013) was a physical therapist who worked in New Zealand. In the 1950's by a chance discovery, he determined that back pain can be treated effectively and quickly with simple repeated movements. Over many years, he implemented his techniques on his patients, developing a system that could be taught to other therapists. Over time his techniques became known as the McKenzie Method and later Mechanical Diagnosis and Therapy - MDT.
This method uses primarily patient generated repeated movements to stress the tissue around joints or in your spine, and assess the immediate effect on the symptoms. If symptoms respond, we have found a directional preference, the starting place for exercise and pain reduction.
Typically, you will be given one to two exercises to perform, frequently throughout the day to reduce your pain. "Passive modalities" such as electrical stimulation, ultra sound, and heat/cold are not used during treatment as they have been found to be ineffective in long term reduction of pain.
One other major tenant of McKenzie's method, is patient education. He believed firmly that as a patient, you should have the knowledge to care for yourself and not be reliant on the medical system. He is famous for his books written for the non-medical person, "Treat Your Own Back" and "Treat Your own Neck", which were written in the 1980's. I agree with McKenzie; you should understand what is the source of your pain and how to manage it yourself, without the need for medical intervention.
Check out this great video