I went with my aunt to the physical therapist's office. I was able to watch how they measured her hip and knee motion before surgery. For some of the measurements, they strapped her leg down to the table. Why is that necessary?

Testing motion of the hip in particular can be affected by position of the pelvis and low back. Using some means of supporting and stabilizing the pelvis and spine assures that the measurements are accurate. If this isn't done, the pelvis can angle in one direction or another giving a false impresssion of hip or leg motion that really isn't accurate.

Given the fact that this was a preoperative measurement suggests the need for reliable, valid, and accurate measurements. Post-operative rehab depends on knowing before and after measurements and gaining improved motion before discharging the patient home and/or progressing the exercise program.

Performing the test the same way each time with each patient is essential to assure standardized measurements. Even with this special methods, measurements can vary from day to day and from therapist to therapist. Keeping a consistent record helps the patient and the therapist at least see general trends in motion.