A robust and semi-automatic quantitative measurement of patellofemoral instability based on four dimensional computed tomography.

•An automatic method to determine the anatomical coordinate frame of femur and tibia.•An automatic method to determine the landmarks of TT-TG (tibial tubercle – trochlear groove) and PC-TG (patellar centre – trochlear groove) distance.•A dynamic quantitative description of TT-TG and PC-TG distance in a patient group (15 legs).•The added value of quantitative measurement based on 4DCT compared to traditional CT scan.