The purpose of this study is to assess the efficacy of the hydrolocalization technique for placement of femoral perineural catheters in comparison with stimulating catheters. A non inferiority trial.

The investigators will randomize patients that will undergo anterior cruciate ligament reconstruction.

Each patient will receive a subgluteal single shot nerve block and a continuous femoral nerve block with placement of a catheter either with the hydrolocalization technique (group HLOC) or a neurostimulating catheter (group NS).

Inclusion Criteria:

• adults
• BMI less than 30

Exclusion Criteria:

• known allergies to local anesthetics or other drugs used
• patient refusal
• any local or systemic contraindication to the use of popliteal block