Inclusion Criteria:  Patient seen at the University Hospital of Reims for an infiltration in the context of pain in low back pain attributable to posterior inter-apophyseal osteoarthritis Patient over 18 years old Patient presenting at least 5 criteria (and criteria 3) (Cochin criteria): Low back pain not exacerbated by cough Lumbalgia well relieved by the decubitus Low back pain not exacerbated when leaning forward Low back pain not exacerbated when getting up Low back pain not exacerbated in hyper extension Low back pain not exacerbated in Extension - Rotation Patient with an MRI dating less than 1 year before inclusion: No herniated disc in the level of the posterior joints to be infiltrated (example: if an infiltration of the post L4-L5 joint is planned, it is considered that there must be no herniated disc at the level L4-L5) Patient having signed the consent Patient affiliated to a social security scheme  Exclusion Criteria:  Contraindications to corticosteroid infiltrations: unbalanced hypertension, unbalanced diabetes, allergy, skin condition next to the infiltration site, not compatible with an infiltration Patient who received corticosteroid infiltration within the last 6 months Patient who has already received an injection of PRP (for the spine or another indication). History of previous spine surgery Presence of an ongoing local or systemic infection Coagulopathy not compatible with performing a deep gesture Pregnant woman and breastfeeding woman Presence of motor deficit Pain less than 4/10 (ENA) Patient protected by law