"Prone to diving headlong into enemy battle lines, Urgot sewed chaos throughout the enemy ranks, often sustaining grievous injuries in the process. When his body was unable to weather further abuse, the crippled Urgot was delegated the position of High Executioner of Noxus. By this time, his hands had been ruined and he could barely walk. Scythe-like grafts affixed to his maimed limbs served to carry out his bloody work."
The lore also states that being cut in half by Garen caused his death. His legs were already kinda obsolete, and I assume by "maimed limbs", they meant his arms. Explains his appearance perfectly.