Gonarthrosis is a chronic pathology affecting the knee joint and tissues. It is characterized by progressive degeneration of articular cartilage, bone and surrounding structures. Diagnosis is based on clinical, biological and radiological criteria.

When knee osteoarthritis becomes symptomatic, it leads to pain associated with stiffness and functional discomfort, impacting on patients' quality of life. Patients become sedentary and isolated, which has cardiovascular and psychological consequences, with a proven excess mortality rate.

To date, there are no curative treatments for gonarthrosis. Available treatments are generally aimed at relieving pain, improving joint function and slowing disease progression. Therapeutic approaches most often combine non-pharmacological treatments such as dietary measures, regular physical activity and therapeutic education, with pharmacological treatments: paracetamol, non-steroidal anti-inflammatory drugs, opioids, intra-articular injections of corticosteroids, hyaluronic acid (HA), Platelet Rich Plasma (PRP)... If these are ineffective, particularly in advanced stages (grades III-IV), then surgery for prosthesis is necessary. However, surgery is not an option for all patients, particularly those with co-morbidities, the elderly or those who refuse it.

The osteoarthritis section of the French rheumatology society has drawn up recommendations, with a view to positioning these treatments, standardizing practices and improving the management of gonarthrosis patients in France. These point out that further studies are needed to validate the efficacy of certain treatments, notably intra-articular PRP injections, which are nevertheless widely used in current practice and defended by a consensus of French experts published in 2021. Indeed, the results of several therapeutic trials and meta-analyses already published show that its efficacy is often superior to that of HA, particularly in terms of symptom improvement and over a longer duration. In order to make the case for their use to learned societies, literature data must be enriched, particularly with regard to advanced stages of gonarthrosis, i.e. stages III-IV, which are the most painful. The aim is to propose an effective treatment to relieve the symptoms of patients for whom surgery is not an option.

In the PAGONA project, the investigators intend to use validated tools (WOMAC questionnaire, EVA scale, EQ-5D-5L quality of life questionnaire) to compare the effect of intra-articular injections of PRP with those of HA on the functional impact of the disease in patients with symptomatic knee osteoarthritis of moderate to severe stages (III-IV), by following these patients for 12 months after their last injection. The investigators plan to conduct a randomized, open-label study at the "Unité de Médecine et de Traumatologie du Sport" (UMTS) at Hôpital Sainte Musse in Toulon, where gonarthrosis treatment using intra-articular injections of PRP and HA is standard practice.

Inclusion Criteria:

1. Age ≥ 18 years ;
2. MRI confirmed grade III or IV unilateral gonarthrosis ;
3. Pain ≥ 3/10 on the visual analogue scale (VAS);
4. Patient with a BMI < 35
5. Patient capable of giving consent prior to participation in the study;
6. Affiliated or entitled under a social security scheme.

Exclusion Criteria:

1. Non-steroidal anti-inflammatory drugs* or corticosteroids** taken in the 7 days prior to inclusion;

2. Local injection of hyaluronic acid in the 2 months prior to inclusion;

3. Local injection of PRP within 1 year prior to inclusion;

4. Local injection of corticosteroids within 5 months prior to inclusion;

5. Current anticoagulant treatment that cannot be stopped during the hyaluronic acid or PRP injection protocol period;

6. Patient diagnosed with any type of cancer in the last 3 years;

7. Pregnant women, women in labour or breast-feeding women;

8. Patients under judicial protection (guardianship, curatorship, etc.) or safeguard of justice;

9. Any other reason which, in the opinion of the investigator, could interfere with the evaluation of the study objectives.

   • Acetylsalicylic acid is allowed when it is prescribed as an antiplatelet agent at doses lower than or equal to 160 mg per day. It has, indeed, no anti-inflammatory effect at these doses.

     • Corticosteroids can be administered when they have a local action different from the one applied to the treated knee (cutaneous, instiled or inhaled routes).