Suggest Treatment For Lumbosacral Spondylosis At L4-S1

My 11 year old son has lumbosacral spondolysis at L4-S1. He's having a CT scan Friday. What are the likely causes and treatments? He's been a competitive swimmer since he was 7 - could this be a contributing factor? He is a big child for his age at 5'6" and 150 lbs. He has no other relevant health issues. This started as pain in the area of his right hip and has gradually gotten worse over several weeks. It hurts him much more with weight bearing exercise and he is currently on exercise restriction.