In a class discussion, fourth graders determined that it's important to figure out how a knee moves, both when it's healthy and when it's unhealthy. This way, when they go to design a brace, they know how the brace should either help or restrict the unhealthy knee's movement.
Students used a special tool to collect data on both types of knees. This tool is known as a goniometer and measures the range of motion for a knee in four directions: backwards, forwards, to the left, and to the right. With careful data collection, fourth graders discovered that their model injured knees could move in two directions that a healthy knee could not move--forwards and towards the outside (extending beyond a normal range of motion).