An employee was attempting to unload a pallet of two tractor wheels with tires that was stood up on end and strapped to the front wall of the trailer. The employee released the strap that secured the pallet to the wall and lowered the wooden pallet to the ground while the tractor wheels remained leaning against the wall. When the employee was walking back to get on a forklift, one tractor wheel fell, struck the back of his calf, and pinned his foot under the tire. The employee sustained a deep contusion to the leg and foot injuries.