Background: Selective unilateral spinal anesthesia is the gold standard spinal anesthesia technique for knee arthroscopy. Selective sensory spinal anesthesia has recently been validated for this surgery. Both selective techniques are specially indicated for ambulatory surgery because of PACU fast track, low discharge home time and high patient satisfaction. This study compares both spinal techniques for knee arthroscopy surgery.

Inclusion Criteria:

• adults scheduled to undergo knee arthroscopy

Exclusion Criteria:

• a previous history of neurological impairment
• insulin-dependent diabetes mellitus
• intolerance to the study drug or related compounds and additives
• BMI > 38 kg/m2
• height <155 cm or >180 cm
• any existing contraindications for spinal anaesthesia
• surgery in which a complete block of the lower limb