Knee osteoarthritis, as a progressive disease is one of the most common causes of pain, motor disorder and disability in the elderly. By increasing age, the cartilage is eroded and endures degenerative changes due to physiological and biomechanical changes as well as metabolic effects and trauma . Non-surgical interventions for pain control of knee osteoarthritis include weight loss, exercise, changes in daily activities, physiotherapy, nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesics .However ,the intra-articular injection is recently recommended by many studies such as corticosteroids, hyaluronic acid, Growth hormone, dextrose ,and platelet rich plasma.

Intra-articular injection of platelets are activated and undergo degranulation, releasing a range of growth factors, including transforming growth factor beta (TGF-β), platelet-derived growth factor (PDGF), insulin-like growth factor, vascular endothelial growth factors, epidermal growth factors and basic fibroblast growth factor 2. These growth factors are thought to activate a variety of signaling pathways, which promote healing of bone and soft tissue.Also,some minimally invasive therapeutic options have been effective in pain relieve in KA, such as ultrasound-guided saphenous nerve block .

The aim of this study is to compare the efficacy of ultrasound guided saphenous nerve block versus platelet rich plasma injection in the management of chronic pain in patients with knee OA. This study will be conducted to evaluate which modality is more effective.

Inclusion Criteria:

• Patients who are not competent to understand the study protocol
• Radiographic evidence of OA of knee of 2nd degree.
• Chronic pain for at least 6 months prior to study entry (day 0).
• Pain relief not achieved with conservative therapies during the last 6 months

Exclusion Criteria:

• Patient refusal.
• Bleeding disorders.
• Coagulation disorders.
• Local skin infection
• Current other problem in the affected extremity .
• Psychiatric disorders affecting co-operation of the patient .
• Previous chronic opioid use.
• Intra articular knee injection within previous three months.
• History of traumatic arthropathy.
• History of neuropathic arthropathy.
• Allergy or hypersensitivity to any of the study medication.
• Any condition that could interfere with the interpretation of the outcome assessments.
• Pregnancy
• Lactating women.
• low back pain due to central cause.