This study aims to assess the long term (three years) ability of ASU (Avocado Soya unsaponifiable) to slow the decrease of radiographic JSW (Joint Space Width) in hip osteoarthritis (OA). This is a randomized, double blind, comparative, parallel group study versus placebo.

Inclusion criteria:

Primary hip OA, fulfilling ACR criteria, patient over 45 y, painful > 1 year, Lequesne's index > or equal to 3, with minimum JSW at the target hip > 1 mm and < 4 mm on pelvic radiograph.

Primary criterion of efficacy:

The main criterion of efficacy is the change of JSW between baseline and end point. JSW is measured on the narrowest joint on pelvic or target hip X ray by blinded reader.

Randomisation is stratified according JSW at baseline (< 2,5 mm or > or equal to 2,5 mm).

Statistical analysis:

The Full Analysis Set (FAS) is defined by patients with at least one baseline value and one post baseline value.

The main analysis is scheduled on FAS using a Missing At Random (MAR)with a multiple model repeated measure (MMRM)to take in account missing value.

SAP (Statistical Analysis Plan) schedule to analyse JSW change as quantitative variable using an ANCOVA and as qualitative variable (progressors defined as JSW loss upper than 0,5 mm) using Mantel Haentzel test.

Inclusion Criteria:

• primary OA of hip,
• ACR criteria,
• older than 45 years,
• symptomatic painful > 1 an,
• Lequesne's index > or equal to 3,
• JSW between 1 and 4 mm on pelvic radiograph.

Exclusion Criteria:

• secondary OA.