An apophysis is a growth plate where a tendon attaches to bone.  If the tendon pulls too hard, the bone of the growth plate might be injured (apophysitis), although rarely is it pulled right off.  The knee is the most common location for trouble, but we see a reasonable number around the pelvis.  The location that the hamstrings come off the back of the pelvis is called the ischium, and is a boney prominence that we sit on.  If injured, this causes a problem both with pain running, and tenderness to sit on.    There may be rare instances that surgery can be considered, for example young athletes.  Before embarking on surgery though, parents and the young athlete need to understand we are trying to achieve what nature is saying is too hard for their body!  If a fragment is substantially displaced, intervention makes sense but the majority of traction apophysitis cases settle with reduction of the activity causing the problem.