1. The injection of procaine into the region of the sacro-iliac joint produces anaesthesia of this joint, which permits the stretching of tight hamstring muscles and manipulation of the joint.
2. This procedure affords a method of determining whether a disorder of the sacro-iliac joint is responsible for the patient's symptoms.
3. Improvement, which was more than transient, resulted in 60 per cent. of a series of patients so injected.