To demonstrate the difference in terms of symptomatic efficacy between ADANT® sodium hyaluronate and placebo following an intra-articular injection in patients with symptomatic osteoarthritis of the hip.

Each patient will receive an injection of sodium hyaluronate or placebo in the symptomatic hip and will be followed up for three months.

At the third month, if the score for overall pain is still > 40 mm on the VAS, a second injection of ADANT® can be given irrespective of which treatment was received previously. The patient will be followed up for a further 3 months in an open-label fashion (monthly visits).

Inclusion Criteria:

• 1. Primary osteoarthritis of the hip defined according to the ACR criteria; symptomatic, 2. Osteoarthritis of radiological grade II to III according to the Kellgren-Lawrence classification, using X-rays performed during the last three months, 3. Overall pain intensity between 40 and 80 mm on a VAS of 100 mm at the pre-screening examination, 4. The patients experienced pain at least one in two days during the last 30 days, it was resistant to paracetamol treatment at a dose of 4 g/day and a step 2 analgesic or a NSAID taken for at least 10 days, 5. A prosthesis is not planned in the next six months.

Exclusion Criteria:

• Women who are pregnant or breastfeeding or women who could become pregnant and are not using effective contraception,
• Major dysplasia (defined using Lequesne's criteria as dislocation of the hip),
• Treatment by intra-articular injection of hyaluronic acid in the symptomatic hip during the 6 months prior to pre-screening,
• Patients with a history of hypersensitivity to any of the ingredients in the hyaluronan,
• The presence of inflammatory arthropathy or another disorder or condition that could affect the joint (e.g., rheumatoid arthritis, metabolic bone disease, femoral head necrosis, psoriasis, gout, infection),
• Another muscular or skeletal condition that could interfere with the evaluation of the efficacy of the treatment on the hip in question (evaluation of pain or functional handicap),
• Systemic corticosteroid therapy or intra-articular injection of corticosteroids into the ipsilateral hip or knee within the last month,
• Intermittent claudication or vascular disease,
• Previous surgery on the hip in question,
• Septic arthritis at any site,
• Any surgical procedure, including arthroplasty or arthroscopy, to the hip during the six months prior to pre-screening or surgery scheduled during the trial,
• Any chronic skin condition that could affect the site of the injection,
• Use of the investigational treatment or material during the last three months,
• Oral or injectable anticoagulant treatment,
• Antiaggregant platelet treatment, particularly low-dose aspirin,
• Symptomatic chondrocalcinosis in the painful hip