Top of my knee and to right, when bending feel grinding and "catching" was told because mri and xrays are normal cartilage is rough and need physical therapy to build muscle? not bad pain more annoying keeps me up at night. could it be something else?

The other possibility would be chondromalacia patella. This is where the muscles of your quadriceps your thigh are imbalanced, and do not pull the patella in the correct alignment with the femur bone of the knee. This occurs with sitting down, bending the knee and going upstairs. This is treated usually successfully by physical therapy exercises to strengthen the quadriceps muscle.