Final answer:
The common cause of in-toeing in childhood is internal tibial torsion. This condition occurs when the tibia bone in the lower leg is twisted inward, causing the foot to turn inward.
Step-by-step explanation:
The common cause of in-toeing in childhood is internal tibial torsion. In this condition, the tibia bone in the lower leg is twisted inward, causing the foot to turn inward. This can lead to a pigeon-toed gait.
Internal tibial torsion is often present at birth and tends to improve as the child grows older. It is usually a benign condition that does not require treatment.