The purpose of the present study is to investigate and compare the potential effects of Hyaluronic acid and atorvastatin on the symptoms of knee osteoarthritis. This open, randomized, parallel study will be conducted on patients with knee osteoarthritis according to American College of Rheumatology (ACR) criteria. Patients will be enrolled from outpatient clinic of Imam Reza Hospital, Mashhad, Iran. Eligible patients are those who meet the ACR criteria of primary knee osteoarthritis, radiologically ascertained grade I or II of knee osteoarthritis on the Kellgren-Lawrence scale, had a pain score=>60 (maximum 100) and age 50-70 years. Patients are not eligible if they have: secondary osteoarthritis, systemic disease like diabetes, history of Inflammatory arthritis, sever knee deformity (varus or valgus >50 degree), history of coagulopathy, sever cardiovascular disease and active infections. We will divide them randomly (via a random number table) into two groups; Group 1 (n=35) will receive intra-articular Hyaluronic acid (Hyaluron HEXAL 20 mg, Germany) each week for three weeks, and group 2 (n=35) will receive oral atorvastatin 40 mg/day orally (Sobhan Darou, Tehran, Iran) for six months. We will train all patients to answer the WOMAC questioner. They will be permitted to continue their usual treatment with analgesics and non-steroidal anti-inflammatory drugs (NSAIDs). However, they are urged not to use analgesics and NSAIDs 48 hours before physician visit to prevent scrambled test results. Symptoms will be scored by WOMAC index at enrollment and every month up to 6 months.