hi,
it may be that:
- Tight Hamstrings:
- restricted flexion of hips due to tight hamstrings may be the only finding;
- 80% of symptomatic pts have tight hamstrings;
- tight hamstrings may be found in pts who have spondylolysis or any grade of Wikipedia reference-linkspondylolisthesis;
- tightness may be extreme, so that child cannot bend forward at hips or, during straight leg-raising test,
examiner cannot lift foot more than a few cm from the examining table;

- Gait:
- tight hamstrings cause peculiar gait (pelvic waddle) in children w/ Spondylolisthesis;
- excessively tight hamstring muscles tilt the pelvis backward and do not permit the hip to flex sufficiently for a normal stride;
- consequently, pt has stiff-legged & short-stride gait, & pelvis rotates with each step.
- child may prefer to jog or run rather than walk, or to walk on the toes with the knees bent;

ref site: www.wheelessonline.com/or...lolithesis