It is proved that the addition of magnesium sulfate to local anesthetics for neuraxial anesthesia improves the quality of analgesia and prolongs the duration of anesthesia . In-vitro and in-vivo studies have demonstrated that magnesium enhances the local anesthetics effect on peripheral nerves .

No previous studies were conducted on magnesium sulfate as an adjuvant to the local anesthetic in genicular nerve block. Hence, this study will be conducted to assess analgesic efficacy of magnesium sulfate when added to bupivacaine in ultrasound guided genicular nerve block

Inclusion Criteria:

• American Society of Anesthesiologist (ASA) I or II physical status.
• Between 18 and 70 years of age.
• Both genders.
• Patients undergoing total knee replacement surgery.

Exclusion Criteria:

• Patient refusal.
• ASA Ⅲ and Ⅳ patients.
• Known allergy to the study drugs.
• Hypermagnesemia.
• Central or peripheral neurological disease.
• Pregnancy.
• Drug or alcohol abuse.
• Localized infection at the site of the block.
• Bleeding disorder (platelets count less than 100,000 or international normalized ratio more than 1.4)