Knee arthroscopy is a minimally invasive day case procedure which may be done for diagnosis, meniscectomy or debridement. Arthroscopic surgery is associated with a variable degree of postoperative pain, which is caused by an irritation of free nerve endings of the synovial tissue, anterior fat pad, and joint capsule due to surgical excision and resection

Many studies were done using different intra-articular agents as local anesthetics, opioids, ketamine and alfa2- adrenergic agonists for prevention and treatment of pain after knee surgeries.

Dexmedetomidine is a potent and highly selective alfa2-adrenoreceptor agonist. It has sedative-hypnotic, anxiolytic, analgesic, anesthetic and sympatholytic effects. Intra-articular dexmedetomidine was used in several studies to enhance postoperative analgesia after knee arthroscopy with an increased time to first analgesic request and a decreased need for postoperative analgesia Neostigmine is an anticholinesterase and also has antinociceptive effects when administered intrathecally or peripherally.

Inclusion Criteria:

• patients aged above 18 years
• scheduled for elective arthroscopic knee surgery under intrathecal anaesthesia

Exclusion Criteria:

• Absolute or relative contraindications for intrathecal anaesthesia,
• Allergy for the studied drugs.
• Patients having history of cardiovascular, cerebrovascular, and respiratory diseases,
• Patients receiving chronic pain treatment or hypertension treated with alfa methyldopa, clonidine or beta adrenergic blockers were excluded from the study.

, Patients were randomly allocated (using random table assignment) into two groups to receive one of the following intra-articular solutions (prepared by an individual not involved in the study) which were injected into the knee joint through the cannular sheath after withdrawal of camera, by the orthopaedic surgeon (who was also unaware of the nature of the study drugs) before the arthroscope removed.