The purposes of this study are to assess the prognostic value of serum and urinary biomarkers Coll2-1 and Coll2-1NO2 at baseline, and their change over the first year, on the progression of knee osteoarthritis MRI scores at 12 months, on the progression of knee osteoarthritis clinical score at 12 months. Additionally, this study will search for correlations between serum and urinary biomarkers Coll2-1 and Coll2-1NO2 at baseline with the radiographic, MRI and clinical severity of knee osteoarthritis.

Inclusion Criteria:

• Male or female, aged 45 to 80 years with a BMI ≤ 40

• With an uni- or bilateral femorotibial knee osteoarthritis associated or not with a femoro-patellar knee osteoarthritis

• Responding to clinical and radiological criteria of the ACR

• Symptomatic for more than 6 months (for the most painful knee)

• K&L radiological grade of Felson II or III

• With a cartilage lesion identified during MRI and either at least 1 out of 4 MRI severity criteria:

  • bone oedema
  • meniscal lesion in the central region of the medial compartment
  • effusion without answer to corticosteroids
  • zone without cartilage

• or at least 1 out of 3 clinical severity criteria:

  • genu varum>3°
  • previous meniscal surgery
  • known polyarthritis
  • effusion on the target knee

• Sign an informed consent after being informed

• Able to follow the instructions of the study

• With an agreement from the physicians having established the diagnosis of osteoarthritis (if any) to give relevant information to the investigator

• With health insurance (for France).

Exclusion Criteria:

For osteoarthritis:

• Isolated patellofemoral arthritis
• Chondromatosis or villo-nodular synovioma of the knee
• Recent trauma-induced knee pain
• Joint disease due to joint dysplasia, aseptic osteonecrosis, acromegaly, Paget's disease, hemophilia, hemochromatosis, …
• inflammatory pathologies as rheumatoid polyarthritis, gout arthritis, infectious arthritis
• Diseases that may interfere with the evaluation of osteoarthritis (radiculalgia of lower limbs, arteritis, …)
• Genu valgum (degree considered as pathological by the physician)

For previous treatments:

• Treatment with strontium ranelate, bisphosphonates, SERM and PTH

For known associated diseases:

• Serious associated diseases: severe liver or renal failure, uncontrolled cardiovascular disease, HIV, hepatitis B or C
• Knee tumor

For patients:

• Patient who participated to a therapeutic clinical trial 3 months before the T0 inclusion visit
• Patient who are the subject of a judicial protection measure or under guardianship
• Pregnant woman

For MRI contraindications:

• Patient with a pacemaker, an implantable defibrillator, neurosurgical clips, a neurostimulator, cochlear implant, a stent, an insulin pump
• Patient with a ferromagnetic splinter in the body, or having wire sutures
• Serious mobility problem (Parkinson, tremors)