 Chronic low back pain, with or without lower extremity pain, which arises from various structures of the spine constitutes a majority of pain complaints. The sacroiliac joint SIJ has been implicated as the primary source of pain in 10 to 27 of patients with mechanical low back pain below L5 vertebra. The common causes of SIJ pain include a trauma like direct fall on the buttocks, a rear-end or broad-side type motor vehicle accident, and an unanticipated step into a hole or from a miscalculated height, fusion surgery, anterior dislocation, inflammatory and degenerative sacroiliac joint disease and idiopathic. The treatment of SIJ pain remains a therapeutic challenge. Besides physiotherapy and systemic therapies including non-steroidal anti-inflammatory drugs NSAIDs and biologic agents, intra-articular and peri articular injections of SIJ, radiofrequency neurotomy and surgical fusion are often performed for pain relief. However, the success of these interventions has been determined according to the therapeutic efficacy and correct placement of the drug. The image guidance of SIJ injections seems to be important due to the complex anatomy of the joint causing a low accuracy when performed according to clinical judgement only. The feasibility of ultrasound USG guided injection of SIJ has recently been demonstrated resulting in very high success rates up to 90. Various agents being used in SIJ injections include local anaesthetics, corticosteroid, botulinum toxin-A, 12.5 dextrose, phenol-glycerine-glucose P2G and sodium morrhuate cod liver oil extract. SIJ steroid injection is commonly used technique and has been found to be effective to treat SIJ pain. However, the main drawback is short term effect. Borowsky et al reported improvement in visual analog score VAS of 14.1 and reduction of VAS 50 in only 12.50 patients at 3 months after intra-articular steroid 2 mL 0.5 bupivacaine plus 40 mg methylprednisolone SIJ injection. Treatment modalities being currently used do not, in general, address the disease process itself, there is clearly a need to investigate treatments that are more widely applicable for symptom management and which may also directly address the disease process itself. Current research efforts aim at modifying the rate of healing of joint by using biological healing factors which are various growth factors transforming growth factor, vascular endothelial growth factor, fibroblast growth factor, epidermal growth factor, platelet derived growth factor etc. found abundantly in the human blood especially in platelets. The platelet rich plasma PRP is an ideal autologous biological blood-derived product, which can be exogenously applied to various tissues where it releases high concentrations of platelet derived growth factors that enhance the bodys natural healing response. In addition PRP possesses antimicrobial properties that may contribute to the prevention of infections. PRP is now being widely tested in different fields of medicine for its possibilities in aiding the regeneration of tissue with low healing potential. Local injection of PRP is a new modality which has been effectively used for the treatment of Achilles tendon injury in athletes, chronic epicondylar tendinopathy, chronic patellar tendinosis, rotator cuff tear, anterior cruciate ligament injury, gonoarthrosis and plantar fasciitis. The intra-articular injection of PRP into knee joint has been found to reduce the incidence of local inflammatory changes in early knee osteoarthritis. Recently, PRP has been used for low back pain caused by SIJ laxity showing significant improvement in pain scores. However, there is no study at present comparing the efficacy of intra-articular injection of PRP with corticosteroids for the treatment of chronic SIJ pain. Considering the vast potential of PRP and its safety, this study aimed at studying the efficacy of ultrasound guided intra-articular SIJ injection of leukocyte free PRP for chronic low back pain due to SIJ pathology. In the current study, we tested the hypothesis that the SIJ injection of leukocyte-free PRP may be more effective for the treatment of sacroiliac joint pain as compared with steroid injection. 