One assumes that normal alignment is a fundamental requirement for normal function. Changes in the lower limb alignment and the orientation of joint surfaces to each other can generate excessive tissue loads that cause pain and joint damage. Pain and damage will affect the normal functioning of the joint. To investigate the relationship between alignment and function a study was undertaken to examine the lower limb alignment and function of patients with patellofemoral pain syndrome. The QUESTOR Precision Radiograph (QPR) was used to measure the overall lower limb alignment as well as alignment of the knee. A smaller, specialized QPR was developed to investigate alignment of the patella (PF-QPR) and includes lateral, skyline and AP views. The PF-QPR was validated using cadaveric material and multiple observers. A simple method of measuring femoral neck anteversion that also utilized the QPR protocol was developed and compared with direct and CT measures of cadaveric material. To assess normal function a stair climbing gait analysis was performed on a group of young normal subjects to establish a baseline of comparison with the patients.

The PF-QPR results showed that several standard clinical measures were quite variable due to errors in locating the required landmarks. The AP view which located the position of the patella showed a significant relationship between the horizontal and vertical position of the patella for the patients. The more medial the patella the lower the patella suggesting a possible relationship between the vertical and horizontal position of the patella. This trend was not evident for the normal subjects.

The gait assessment on the normal subjects demonstrated that the forces and moments during stair ascent were larger than those during level walking and that the estimated patellar contact forces could reach three times body weight. Maximum values of the various force and moment curves were not significantly different between the normal subjects and the patients.

The comparison of alignment and function revealed two trends. The first was that three patients who had knee moment and patellar force profiles during the push-off phase that were visually different from normal had the most medialized patella. For these three patients the larger the patellar force the more medial the patella's position. The second trend was that the patient that walked with the greatest degree of internal rotation had the most laterally displaced patella while the patient with the most medially displaced patella had the greatest degree of external rotation.

The results suggested that the PF-QPR is useful in the measurement of patellar alignment and that patellar alignment is an important aspect of lower limb alignment. The relationships found between alignment and patellar forces support the hypothesis that normal alignment is a requirement for normal function.