The blocks are what hold the nerves, so when one of them slips, it may pinch nerves causing pain. Because this type of spondylolisthesis most often occurs in the lower back, the pain usually involves the lower back, buttocks, and upper legs. However, certain sports like gymnastics, weight lifting, and football may cause this to progress causing symptoms. The treatment for spondylolisthesis may range from none to surgical intervention. Most of the time, a brace may be applied and the child given pain and anti-inflammation medications.
Physical therapy is often necessary to strengthen and stretch muscles.
However, when the slip is extreme or the symptoms severe, surgery may be required to put the wooden block back where it should be. I am very sorry to hear of your boy's pain. I am sure this is a difficult time for both him and your family. Treatment will require a good team approach with you, your family, your son, and his doctor all as contributing members. Remember each part of therapy is as important as the other.