Stephanie was diagnosed with scoliosis, a curvature of the spine, when she went for a regular checkup with her doctor in her sophomore year of high school. Her doctor could see the curve in Stephanie's spine through her skin when she bent forward. In order to determine whether Stephanie's curved spine needed treatment, the doctor referred her to an orthopedic specialist. The orthopedic doctor took x-rays of Stephanie's bones to determine the extent of the curve. Stephanie was surprised to learn that he was also very interested in the amount of cartilage in her bones. The orthopedic doctor said he wanted to know how much more her bones were likely to grow in the coming years. If her bones were almost done with their main phase of growth, her scoliosis was more likely to stay stable as it was. If there was a lot of cartilage left in Stephanie's bones, the curve might have a greater potential to change and get worse over the coming years. This information could help to determine the level of treatment the doctor would recommend to Stephanie. In what area of a long bone would it probably be easiest to observe the cartilage the orthopedic doctor refers to?