The goal of this clinical investigation is to evaluate the effectiveness on pain of arterial occlusion (embolization) of neovessels by microparticle in a double-blind sham controlled randomised trial in patients with persistent pain on a total knee prosthesis (TKP), inserted for gonarthrosis, despite well-conducted medical treatment. The study patient population will consist of up to 112 subjects with knee pain for at least 3 months that is resistant to conservative treatment measures. Subjects will be treated with knee embolisation or saline in the sham arm. The efficacy of embolization will be judged on the basis of the following criteria: improvement in pain, mobility, use of pain medication, adverse effects of embolization and duration of improvement.

After verification of eligibility criteria, patients with painful total knee prosthesis will be randomized to either the embolization group or the control group. Embolization will be performed using microparticles (Embozene® Microspheres 100 microns from Varian), for the treatment group. For the "sham " group, only diagnostic arteriography will be performed without injection of microparticles. Subjects will be followed up at 1, 3, 6 and 12 months.

Rational: One hundred thousand total knee replacements (TKRs) are fitted annually in France. Twenty percent of patients who have undergone a TKR have residual pain unrelated to a technical fault or loosening. This pain is a major handicap in everyday life, with no effective therapeutic solution. Arterial embolization for therapeutic purposes is rapidly gaining ground in a variety of pathologies. Its use in intractable synovitis and osteoarthritis appears particularly attractive. To date, no randomized controlled study has been conducted to assess the analgesic effects of arterial embolization in patients with symptomatic TKR. A study of 12 patients at the CHU de NICE showed good tolerance of the technique and a significant effect on the KOOS 12 pain score, which improved by 38% at 3 and 6 months. In view of the results of this study, and in this situation of therapeutic impasse, it seems appropriate to evaluate this technique in a randomized, controlled therapeutic trial, which could offer real therapeutic hope

The main objective this double-blind (patient and evaluator), randomized, prospective study is to evaluate the effectiveness of embolization on the pain of patients with persistent pain on a total knee prosthesis by double-blind comparison of two groups at 3-months: the first control group (sham) will include patients who will benefit from arteriography and an injection of saline in their neovessels. The second group, called treatment group, will consist of patients whose neovessels will be occluded by inert microparticles of 100 µm. The pain will be evaluated in both groups before and 3 months after embolisation. The objective is to show that the pain is significantly less important in the group of patients whose neovessels have been occluded with microparticles in comparison to the control group.

Secondary objectives are to evaluate the effectiveness of neovascular embolization on pain, symptoms and functional limitation, knee stiffness, physical activity, quality of life, use of analgesics and anti-inflammatories over the 12 month-follow-up period. The safety and the medico-economic impact will also be evaluated.

Study Population: 112 patients aged 40 to 80 years with a painful total prosthesis with a visual analogue scale (VAS) score greater than or equal to 40 mm for at least 3 months despite an optimal medical treatment, and investigations ruling out malpositioning, loosening and sepsis of the prosthesis,

Primary endpoint: modification of the pain item of the self-administered 12-item Knee injury and Osteoarthritis Outcome Score (KOOS-12) between baseline and 3 months.

Secondary evaluation criteria are KOOS-12, VAS (visual analogic scale), AMIQUAL (Quality of Life Scale) at baseline and then at 6 months; the use of analgesics and anti-inflammatories; adverse effects, medico-economic impact of embolization.

Expected benefits: This study should contribute to improving knowledge in the field of knee prostheses and, more generally, knee osteoarthritis and its management. More importantly, should the study prove conclusive, the results would enable us to extend the use of embolization treatment to all patients with chronic pain following knee prosthesis. At a societal level, health savings could be envisaged thanks to lower consumption of care and prolonged autonomy.

Inclusion Criteria:

• Man or woman aged between 40 and 80 years with a TKR for more than one year.
• TKR pain with a VAS ≥ 40 mm having progressed for at least 3 months despite the initiation of a well-conducted medical treatment including stage I and II analgesics and NSAIDs in the absence of contraindication.
• Investigations within 6 months to rule out malposition, loosening and sepsis (conventional X-rays, bone scan, knee CT scan and biological work-up for inflammatory syndrome).
• No revision surgery envisaged.
• Echodoppler hyperemia over the painful area of the knee.
• Subjects affiliated to social security.
• Signed consent to the study.

Exclusion Criteria:

• Local infection of the TKR or systemic infection.
• Algoneurodystrophy.
• Prosthesis loosening.
• Neuropathic pain.
• Allergy to contrast media.
• Fibromyalgia.
• Chronic or acute renal failure (clearance < 30 ml/mn).
• Hemostasis disorders (platelet count < 50,000/mm3 or patient activated partial thromboplastin time (aPTT)/control aPTT>1.2 or prothrombin ratio < 50%).
• Operative indication for removal of the prosthesis retained
• Patient with severe obliterative arteriopathy of the lower limbs (Leriche et Fontaine stage 3).
• Lidocaine contraindication: known hypersensitivity to lidocaine hydrochloride, amide-bonded local anesthetics or any of the excipients; patients with recurrent porphyria.
• Vulnerable persons (minors, patients under guardianship or curatorship, deprived of liberty, under court protection, etc.).
• Pregnant patients: for patients of childbearing age, a pregnancy test will be performed during the screening visit.

Only the interventional radiologist cannot be blinded, given the procedure (embolization with microparticles) . This means that the patient and the principal investigator at each center involved in the clinical evaluation of the patient will be blinded.