The provision of anaesthesia through techniques devoid of opioid is referred to as opioid-free anaesthesia. Both pain crisis in sickle cell (SC) disease and poor postoperative pain care worsens patient morbidity. This is a case report of a 22-year-old female SC anaemia patient, who had bilateral quadricepsplasty. Sickle Cell disease is common among individuals of African race and opioids are often abused during the out-of-hospital treatment of pain crisis. We report the case of pentazocine addiction resulting in severe bilateral quadriceps fibrosis. Thus, it was necessary to avoid opioid-based anaesthesia. A combined spinal epidural anaesthesia using magnesium adjunct was applied. The analgesic function of magnesium is linked to the blockade of the N-methyl-D-aspartate receptor. The subarachnoid block was achieved with 3.5 mL of 0.5% heavy bupivacaine (17.5 mg), while epidural anaesthesia was done with 14 mL of 0.25% plain bupivacaine (37.5 mg) and 1 mL of 2 mg/kg of magnesium, (i.e., 120 mg). After the surgery, the surgical sites were infiltrated with 10 mL of 0.25% plain bupivacaine (25 mg) on each limb. Intravenous magnesium-sulfate 5 mg/kg (i.e., 300 mg), was added to 500 mL of crystalloids to run every 4 h. Furthermore, 1 mL of 2 mg/kg magnesium, (i.e., 120 mg,) was added to the 14 mL of 0.125% plain bupivacaine to make 15 mL of magnesium–bupivacaine admixture, every 4 h. These were given for 48 h. The Visual Analog Scale pain scores reduced from 9/10 to 5-6/10 and then to 3/10 over a 6-h period and remained at or lower than 3/10 throughout the postoperative period. Adequate haemodynamics, oxygenation, hydration, warmth, and urine output were ensured. The postoperative period was crisis free.