The purpose of this study was to evaluate the physical features of pediatric patients with lumbar spondylolysis (LS), factors that increase the load during compensatory movements at the lumbar spine, and the outcomes of rehabilitation. Twenty patients were included. Fifteen items were used:fingertip-to-floor distance (FFD), straight leg raising (SLR), heel-to-buttock distance (HBD), tightness of the rectus femoris, the lateral and medial rotator muscles, iliopsoas, tensor fascia lata, adductor muscles, soleus muscle, and latissimus dorsi, and trunk rotation, sit-ups and endurance of the abdominal and back muscles. Initial findings were judged as positive or negative using previously reported cut-off values and were re-evaluated 2 or 3 months later. Positive tests were found for HBD and tightness of the rectus femoris in 85% of the patients, for endurance of the abdominal muscles in 75%, SLR and sit-ups in 70%, and FFD and tightness of the external rotator muscles in 60%. The physical features varied according to the type of sport played, and some patients were refractory to rehabilitation. Only 17.6%, 33.3%, and 40.0% of patients with initially positive findings for HBD, tightness of the external rotator muscles, and endurance of the abdominal muscles, respectively, achieved improvements after rehabilitation. J. Med. Invest. 65:177-183, August, 2018.