Patellar luxation in dogs and cats means the knee cap or patella can be moved or is fixed out of its normal position either towards to inside of the joint (medial patellar luxation or towards the outside of the joint (lateral patellar luxation). Medial is th emost common direction of patellar luxation in dogs.
Patellar luxation surgery normally includes a sulcoplasty (deepening of the groove), tibial tuberosity transposition (TTT) so the angle of the tibial tuberosity is realigned to correct the direction of the pull of the patellar ligament. The joint cvapsule is also then tighened at closure, meaning 3 procedures are performed in one surgery.
More advanced techniques including tibial and femoral osteotomies may be necessary in more severe cases, however fortunately this is uncommonly required.
Assessment of the groove depth and orientation in which the patella should run in at patellar luxation surgery.
The abnormal luxation of the patella damages the cartilage surface of the joint, in particular the articular surface underneath the knee cap (patella) as can be seen by the loss of smooth white cartilage in this photo and exposure of the bone in this photo.
This is irreversible damage which could have been avoided had surgery been done to correct the alignment when the dog was much younger. The alignment can still be corrceted now, but the damage to the joint is more severe.
Close up of area of patellar cartilage loss beneath the patella in a 6 year old dog