During the pre-anaesthetic evaluation, the patients fitting the inclusion criteria will be given a baseline Visual Analogue Scale (VAS) to record baseline pain levels. The patients receiving femoral nerve block with 0.2% ropivacaine will be placed in group F

and the patients receiving adductor canal block with 0.5% ropivacaine will be placed in group A.

The patients will receive the respective blocks postoperatively under USG guidance, either in the operation theatre or in the post anaesthesia care unit. Standard techniques as described ahead shall be followed for each patient at the hands of an

experienced anaesthesiologist. For the femoral nerve block group The transducer will be placed transversely at the inguinal crease, and the femoral vessels will be located. If multiple arteries are present (i.e., superficial and deep femoral arteries), then the probe will be slid proximally until only the common femoral artery is visualized along with its associated femoral vein. Immediately lateral to the femoral vessels, the femoral nerve classically appearing as a hyperechoic wedge or ovoid structure will be identified. Once the femoral nerve and relevant neighbouring structures have been identified, a 2% Lignocaine wheal will be administered before the block needle insertion into the tissue, and the needle tip is advanced below the fascia iliaca towards the femoral nerve

Confirming negative aspiration for blood, a mixture of 15ml of 0.2% ropivacaine plus 10 ml of 2% lignocaine with adrenaline and 1ml (4mg) dexamethasone will be injected with the ultrasound monitor showing the spreading of the drug around the nerve

For adductor canal block The transducer will be placed anteromedially, approximately at the junction between the middle and distal third of the thigh. If the artery is not immediately obvious, several manoeuvres will be used to identify it, including colour Doppler scanning to trace the femoral artery caudally from the inguinal crease. Once the femoral artery has been identified, the probe will be moved distally to trace the artery until it passes through the adductor hiatus to become the popliteal artery. Adductor canal nerve block will be performed more proximally, around the mid-thigh level. The needle will be inserted in-plane in a lateral-to-medial orientation and advanced toward the femoral artery, after a 2% lignocaine wheal will be raised at site of injection. 15 ml of the respective concentration of Ropivacaine and 10 ml of 2% Lignocaine with Adrenaline with 1ml of Dexamethasone (4mg). Maximum pain score using VAS will be recorded in the Post-anaesthesia Care Unit (PACU) and in wards at 0, 24, 48, and 120 h after surgery. Pain scores using VAS at rest and at movement will be recorded at 24, 48, and 120 h post-surgery. Patients’ satisfaction will be scored on a scale of 0 to 10, which indicates absolutely no satisfaction to absolute satisfaction at 24, 48, and 120 h post-surgery. Mobilization, walking distance, and range of knee motion with maximum knee extension in degrees and maximum flexion in degrees will be entered in the database at 24, 48, and 120 h post-surgery. In the period of 120h, if the pain score exceeds 4/10 rescue analgesia in the form of Injection Paracetamol 1g iv shall be given. If pain scores fail to improve despite Injection Paracetamol, Injection tramadol 50mg slow in 100cc normal saline with slow Injection Ondansetron 4mg shall be given. Total cumulative dose of rescue analgesic as well as the earliest point of time when rescue analgesic was needed will be recorded.