The thesis investigates the hypothesis that the conformation and gait of the
hind limb of certain large breeds of dog predisposes to rupture of the cranial cruciate
ligament. It is divided into three parts.
The first part studies the breed incidence of cranial cruciate ligament rupture in
dogs. The second compares the gait and conformation of the hind limb, with
particular attention to the stifle joint, in two large breeds of dog, the Rottweiler, in
which cruciate damage is common, and the Racing Greyhound, in which it is rare.
The third part compares the biomechanical properties of the cranial cruciate ligament
and osseous geometry of the tibial plateau in the two breeds.
A survey of 72 general practices and 4 veterinary school case records showed a
high incidence of cranial cruciate ligament rupture in the Rottweiler relative to its
popularity in the general dog population and a lower mean age at the onset of clinical
signs compared to all the other breeds affected. Cruciate ligament damage was rarely
reported in the Racing Greyhound.
Conformation and kinematic gait analysis of 28 Rottweilers and 28 Racing
Greyhounds was done with a high speed cinecamera, recording at 50 frames per
second, and a microcomputer-based gait analysis system. Frame by frame analysis of
the cinefilm showed that the hind limb joints of the Rottweiler exhibited statistically
significantly greater ranges of angular motion during the walk and trot compared to
the Racing Greyhound. The stifle joint was more extended in the Rottweiler at the
commencement of weight-bearing and the stride length was greater, which together,
lead to a
tendency to overextend the stifle joint stressing the cranial cruciate
Biomechanical testing of cadaver stifles in 13 Rottweilers and 15 Racing
Greyhounds, at the flexion angles determined from the gait analysis, examined the
stability of the joints and the material and structural properties of the cranial cruciate
ligaments and their bony attachments when loaded in tension. The geometry of the
tibial plateau was also investigated. The stifle joints became less stable with
increasing joint flexion, the Rottweiler joint being consistently more lax than the
Racing Greyhound. This may explain the tendency of the Rottweiler stifle joint to
extend more fully than the Racing Greyhound, which is recognised as one
mechanism of cranial cruciate ligament rupture. In extension, the tensile strength of
the Racing Greyhound cranial cruciate ligament was statistically significantly greater
than the Rottweiler, although the strength of the latter increased with increasing joint
flexion. The contact angle between the femoral condyles and the tibial plateau
changed as the joint was flexed, more so in the Rottweiler where there was a greater
backward slope of the plateau.
The conformation and gait of the Rottweiler hind limb does influence cranial
cruciate ligament damage. The normal Rottweiler stifle joint is more extended than
the Racing Greyhound at foot placement when the cranial cruciate ligament is
weaker. As the joint flexes, the ligament is stronger but the greater backward slope
of the tibial plateau contact point results in a greater force tending to move the tibia
forward relative to the femur which must be counteracted by the cranial cruciate
ligament. Therefore as the Rottweiler stifle joint flexes from full extension, the
ligament and its attachments become biomechanically stronger but the load on the
cranial cruciate ligament becomes greater.