A corked thigh is a common injury in contact sports caused by a direct hit to the thigh muscle. Also known as a dead leg or a charley horse, a corked thigh is technically a hematoma or contusion. A hematoma occurs when your muscle gets bruised causing internal bleeding. It can be incredibly painful as your thigh starts to swell and inflame with symptoms such as: Inability to walk, run, or climb stairs Sitting and lying down can become uncomfortable Inability to bend the knee or hinge at the hips Swelling and tightness in the thigh muscle Bruising Mild to severe pain