 The traditional method used to treat this type of pain uses multiple injections to target the nerves supplying the joint. This method is however both time consuming and the results are variable depending upon the number of injections. Therefore a new electrode, called the Simplicity III, was developed to allow the treatment to be undertaken using fewer injections. Although this treatment has received formal approval, undergone conformity assessment and is available in certain specialist NHS centres for clinical use, there is presently limited evidence with regards to its clinical efficacy. We wish to test the effectiveness of this new device in treating sacroiliac joint pain. The best way to prove the clinical effectiveness is to compare Simplicity III against an identical procedure where the electrode is not switched on and neither the patient nor the doctor is aware whether it was switched on. Once pain has been assessed at 3 months, those patients not receiving active treatment and remaining in pain will be offered the active treatment. 