Cranial Cruciate disease Anatomy The Cranial cruciate ligament is located in the stifle joint (or knee). It is a thick fibrous band that runs from the distal femur to the proximal tibia. It is designed to prevent tibial thrust (forward motion of the tibia relative to the femur) and internal rotation of the stifle. It crosses with the Caudal cruciate ligament. Pathogenesis Cranial cruciate rupture occurs in all breeds of dogs and can occur at any age but it is most common in larger breed dogs in middle to older age. There are a few theories as to why it happens but the most commonly believed is that it is multiple factors that contribute to rupture of the ligament. One postulated theory is that we see loss of blood supply and weakening of the ligament in older dogs. Coupled with weight gain, relative lack of activity and trauma (sharp twisting or jumping) the ligament is caused to rupture. Predisposing factors Breed some dogs (Labradors, German Shepherds etc) have a very steep tibial plateau which means that the relative forces of the femur in relation to the tibia are enhanced which increases the risk of ligament rupture. Dogs that suffer medial patella luxation (American Staffies, Bulldogs etc) are at increased risk of cruciate ligament damage.
Weight extra weight in dogs leads to additional loading on the stifle joint which increases the chance of rupture. Activity inactivity leads to weakening or loss of tone of the quadriceps muscle which is a protective mechanism for the stifle joint and cruciate ligament. Very active dogs maintain better muscle tone but because of their high energy levels are more likely to suffer a traumatic episode during which the ligament can rupture. Clinical symptoms Partial tear Dogs will often limp on the affected leg with steady improvement but not full resolution over a period of 2-4 weeks. They will sit with the leg tucked under their body or out to the side to relieve pressure on the stifle. Initially dogs will toe touch when standing Full tear, no meniscal damage As for above but the limp is more severe and takes longer to improve and will unlikely fully resolve Full tear, meniscal damage These dogs are severely lame and although some comfort will return in time the limp remains quite significant. Sometimes a clicking sound can be heard intermittently while the dog is walking. Toe touching Positive sits test
Diagnosis Diagnosis is achieved with a combination of examination and X-rays. In very calm dogs with full rupture this can be easily detected in consult. In nervous dogs and very large or strong dogs, or dogs with only a partial tear we often need to perform the examination while sedated. Radiographs are taken to rule out other pathology of the stifle joint, assess for arthritis and to plan for surgery. Stifle effusion and osteoarthritis Test for cranial drawer in the stifle Treatment Conservative In very small dogs with partial or complete rupture with no meniscal damage rest, anti-inflammatories and chondroprotectants can achieve a result similar to surgery. This is mainly in dogs under 5kg in weight.
Lateral suture Placement of an artificial suture on the outside of the joint to mimic the cruciate ligament is a common technique used in dogs up to 15kg and can be very effective. It can be used in larger dogs but other techniques do give superior results (see below). Lateral suture placement TTO/TTA/TPLO These procedures all utilize alterations in the biomechanics of the stifle to achieve stabilization and return to function. These procedures aim to, in isolation or combination, reduce the angle of the tibial plateau thus reducing the shearing force of the femur on the tibia as a result of the loss of the cruciate ligament and advancement of the tibial crest increases the pull of the quadriceps muscle and thus stabilizes the stifle joint reducing tibial thrust. TPLO TTA TTO
Recovery from surgery Most dogs recover well from surgery but it is very important that they are kept confined while the repair heals. In dogs that have had a lateral suture repair this is generally for 2-4 weeks initially with gradual increase in very controlled activity to 12 weeks. In dogs that have had TTO/TTA/TPLO they need to be confined for 6-8 weeks initially while the bone heals. Thereafter they have a slow return to full activity.