Sever's Disease, otherwise known as apophysitis of the calcaneus, is an inflammation of the growth plate in the heel of growing children. The condition presents as pain in the heel and is caused by repetitive stress to the heel and is thus particularly common in active children. It usually resolves when the bone has completed growth or activity is lessened. Sever's Disease, otherwise known as apophysitis of the calcaneus, is an inflammation of the growth plate in the heel of growing children. The condition presents as pain in the heel and is caused by repetitive stress to the heel and is thus particularly common in active children. It usually resolves when the bone has completed growth or activity is lessened.