Luxating Patellas in Toy and Miniature Breeds
October 1, 2008
My friend Paul, at Purina, is one of those pet owners that brings his little poodle in to work most days. Cookie is a one year old miniature poodle and according to Paul she has a common miniature poodle problem. It seems that Cookie has a knee cap or patella that won't stay in the groove. It slips off the femur towards the inside of the knee rendering the back leg temporarily useless.
Paul just returned from a visit with his veterinarian and got the bad news and a treatment plan to help get Cookie on the road to recovery. Naturally Paul has a few questions about the condition, the treatment plan and the prognosis, or most likely outcome, should he elect to go with the vet's treatment plan.
The normal kneecap or Patella is the bone that basically connects the upper leg with the lower leg. On the upper end it is attached to the large muscle groups of the thigh via the quadraceps tendon and on the lower end attached to the tibia via the patellar tendon. The patella lies in a groove in the distal or lower end of the femur and slides up and down within this groove as the lower leg is flexed or extended. It forms a crucial lever and is critical to the normal function of the hind leg in the dog and cat.
Imagine what would happen if the patella slid out of the groove towards the inside of the knee or imagine if the rope in a pulley mechanism slipped out of the groove in the pulley. There would be no lever action and it would be very difficult and painful to try to move the lower leg.
This is exactly what happens to Cookie several times a day. One moment everything is fine and Cookie is running and jumping normally and the next she's on three legs with one of the hind legs extended straight behind her. She doesn't appear to be in terrible pain and Paul has even mentioned that she scoots around pretty well on three legs.
Over time this abnormal movement of the patella can cause serious degenerative joint disease and the pain associated the arthritis is actually worse than the initial pain of the luxation. Anyone that has ever had arthritis in the knee joint and has to negotiate stairs knows what this pain feels like.
Many Toy or Miniature breeds are born with shallow grooves in their femurs and other abnormalities that mis-align the entire quadriceps mechanism that controls much of the activity in the hind leg. These congenital abnormalities are graded from grade 1, where the patella can only be manually pushed out of the groove and the gait is normal, to grade 4 where the patella is always dislocated and the poor pooch is forced to walk on three legs all the time.
Sounds like Cookie is in grade 2 where the patella spontaneously slips in and out and intermittent lameness results. Grade two means it's time for corrective surgery. There are some physical therapy techniques that can be applied in grade 1 and early grade 2, but in Cookie's case surgery is the only hope for a normal gait.
There are two basic types of surgery. The first attempts to tighten up the tissue around the knee. This is referred to as imbrication and involves suturing tissues around the knee together which helps keep pressure on the patella in the femoral groove so it is less likely to slip out. This works in some cases but usually the second type of surgery is required for a complete fix especially in dogs like miniature poodles.
This surgery involves deepening the femoral trochlear groove. Trochlear recession sulcoplasty is the preferred surgery as it preserves the articular cartilage in the groove which reduces the likelihood of severe arthritis later in life.
The outcome in a young dog like Cookie with relatively early stage pathology is excellent with the recommended surgery. There may be complications due to arthritis later in life even with the surgery but without it you can guarantee that the condition will get worse over time and more severe arthritic changes will almost certainly take place.
The surgeries aren't cheap and often will need to be performed on both legs. You could be looking at up to $1000 per leg for the surgery alone with the diagnosis and aftercare not included.
One more reason for many of us to consider Pet Health Insurance.
This article is based on a post originally published by Dr. Larry as Guest Author on the ScratchingsandSniffings.com blog and is used here courtesy of Yvonne DiVita.
This information is being provided for informational purposes only and is not intended as specific veterinary advice for your cat or dog. It should not be considered or used as a replacement for any qualified veterinary care.
Back