The value of corticosteroid infiltration of the meniscus wall in the therapeutic strategy is not clearly defined: the data in the literature on the effectiveness of corticosteroid infiltration are heterogeneous and of low level of proof. We hypothesize that corticosteroid infiltration of the meniscal wall under ultrasound control would be effective for rapid relief of degenerative meniscal pain.

The main objective is to evaluate the efficacy of ultrasound-guided meniscal wall infiltration of betamethasone versus ultrasound-guided meniscal wall infiltration of placebo, at 1 month, on meniscal pain in the treatment of meniscal pain of degenerative origin in adult.

"Meniscal pain" is a very frequent cause of consultation in orthopedics, rheumatology or sports medicine. The management of degenerative meniscal lesions has been the subject of a consensus conference by the French Authority (2008) and a recommendation by the European Society of Sports Traumatology, Knee Surgery and Arthroscopy (ESSKA 2017), which propose symptomatic medical treatment before any surgical management. Conservative medical treatment is the first-line treatment for most patients with symptomatic meniscal injuries with a wide range of therapies including rehabilitation, oral nonsteroidal anti-inflammatory drugs, joint injections of corticosteroid, hyaluronic acid, or platelet concentrates, as well as injection of corticosteroids into the posterior meniscal wall. In the therapeutic arsenal, corticosteroid infiltrations of the posterior meniscus wall are those that have been the subject of the most clinical studies, yet the data in the literature on the efficacy of these corticosteroid infiltrations are of low level of evidence. This is why the European Society of Musculoskeletal Radiology's Delphi-based consensus group on musculoskeletal imaging (ESSR) is encouraging the development of clinical research in this field with a placebo control group, in order to allow an objective validation of perimeniscal corticosteroid injection procedures in the treatment of meniscal pain of degenerative origin.

The present study is a multicenter randomized controlled trial in double blind (patient and evaluator) versus placebo. Only the physician performing the infiltration will know the status of the group assigned to the patient (experimental or placebo).

Enrollment will be prospective from the active line of patients followed in the investigating centers. A telephone pre-inclusion visit will be done at least 7 days before the inclusion visit. The inclusion visit, randomization (stratified on the centre) and infiltration will be performed on the same day. The follow-up will include a consultation at 1 month and two phone call at 7 days and 3 months.

Inclusion Criteria:

• Localized knee pain with tenderness over the medial or lateral joint space reproduced on clinical examination
• Pain assessed with a VAS score > 4/10 despite first-line medical treatment including the use of tier I or II analgesics or NSAIDs.
• An MRI of the knee performed in the 6 months preceding the operation as part of the pre-treatment assessment
• Medial or lateral degenerative meniscal lesion on MRI consistent with pain, confirmed by an investigating physician
• Affiliation to the Social Security
• Free and informed consent signed by the patient

Exclusion Criteria:

• Patient under curatorship, guardianship or safeguard of justice
• Inability to speak, read or write French fluently
• Patient deprived of liberty
• Patients with psychiatric pathology
• Patient who has had an MRI showing an unstable meniscal lesion: complete vertical tear of more than 10 mm in length, capsulomeniscal disinsertion of more than 10 mm in length, complex tear, T2 hypersignal tear of liquid type with passage of liquid testifying to the spreading of the edges, tear with displaced meniscal fragment, lesion of a posterior meniscal brake, lesion of the meniscotibial or meniscofemoral attachment
• Patient with an MRI showing recent ligament injury(ies) (cruciate ligaments and/or collateral ligaments)
• History of knee trauma less than 3 months
• History of arthroscopy or open surgery of the involved knee,
• History of corticosteroid injection in the knee concerned in the 3 months preceding inclusion,
• Use of NSAIDs and oral corticosteroids during the 48 hours preceding inclusion
• Use of tier 3 analgesics for gonalgia in the 3 months prior to inclusion
• Episodes of knee instability or true locking
• Radiographic gonarthrosis with a Kellgren Lawrence stage >1 authenticated on radiographic images taken within the last 6 months.
• Known inflammatory rheumatism
• Fibromyalgia as determined by the clinical investigator
• Pregnancy and breastfeeding in progress
• Contraindication to the use of injectable corticosteroids: septic arthritis, skin lesions at the injection site, severe coagulation disorders, hypersensitivity to one of the excipients
• Contraindication to the use of systemic corticosteroids: acute infection, untreated and uncontrolled chronic infection, psychiatric or ophthalmological pathologies, unbalanced diabetes, uncontrolled hypertension
• Contraindication to the use of lidocaine: known hypersensitivity to lidocaine hydrochloride, to local anaesthetics with an amide bond or to one of the excipients, patients with recurrent porphyrias
• Patients on anticoagulants

This trial will be double-blind (patient and evaluator). Only the physician performing the infiltration will know the status of the group assigned to the patient (experimental or placebo).