Fig 1.
The measurement definitions of the joint angle and anatomical trochlear angle (AT angle).
The joint angle (white arc) was measured as the caudal angle of the anatomical axes of the femur and tibia. The distal femoral anatomical axis was defined as the extension of the line connecting the two points (white squares, A and B). The distal point A was the centre of the femoral width, which was one femoral condyle length (line FCL) away from the proximal extremity of the trochlea, and the proximal point B was half the FCL away from the distal point. The proximal tibial anatomical axis was defined as the extension of the line connecting the centre of the tibial width (black square) and the notch at the front of the tibial plateau. The tibial width was measured at the tibial cortex, which was 1.5 times the length of the proximal tibial width (PTW) away from the notch at the front of the tibial plateau. The AT angle was measured as the caudal angle made by the femoral anatomical axis and the femoral trochlear line.
Fig 2.
The measurement definitions of the patellar length (PL), patellar ligament length (PLL), and size of the femoral condyle (FC).
The PL was measured as the longest dimension of the patella. The PLL was measured from the most distal portion of the patella to the patellar ligament insertion on the cranioproximal portion of the tibial tuberosity. The FC was measured from the origin of the long digital extensor muscle to the caudal femoral cortex along the Blumensaat’s line.
Fig 3.
The measurement definitions of the femoral trochlear length (TL), proximal patellar position (PPP), and distal patellar position (DPP).
The TL was measured from the proximal extent of the femoral trochlear ridges to the origin of the long digital extensor muscle. X is the distance from the proximal end of the TL to the proximal edge of the patella. The PPP was defined as X/TL. Y is the distance from the proximal end of the TL to the distal edge of the patella. The DPP was defined as Y/TL.
Table 1.
The breed, sex, median body weight (range), and median age (range) of the dogs in the medial patellar luxation (MPL) and control groups.
Table 2.
Mean values (standard deviations) of the measurement ratios and angles of the MPL and control groups.
Table 3.
Results of simple linear regression analyses for PPP or DPP and stifle joint angle, sex, age, body weight, or limb side.
Table 4.
Final models of the multivariable regression analyses for PPP or DPP and morphological factors.
Table 5.
Final models of multivariable linear regression analyses for PPP or DPP and the presence of MPL.
Table 6.
Final models of multivariable linear regression analyses for DPP and the grade of MPL.
Table 7.
Final models of multivariable linear regression analyses for PLL/PL, AT angle, FC/PL, TL/PL, or TL/FC, and the presence of MPL.
Table 8.
Final models of multivariable linear regression analyses for AT angle, FC/PL, TL/PL or TL/FC, and the grade of MPL.