Abstract: This instrument for surgical treatment, in particular for tenolysis, tenotomy or neurolysis, comprises a main body and a distal part. The distal part has a curved portion forming a hook and is provided with a cutting blade on the inner side of the hook. The main body has a longitudinal lumen for passage of fluid from a proximal end to a distal end of the main body, as well as an elbow with concavity facing the same side as the hook such that the main body has, in the vicinity of its distal end, an injection channel which is in fluidic connection with the lumen via an over-pressure chamber.