The canine knee joint, known as the stifle joint, is similar to a human’s knee in many regards. The joint is made up of the meeting of the femur (thigh bone), tibia (shin bone), and the patella (kneecap). The cranial and caudal cruciate ligaments (CCL), medial and lateral collateral ligaments, and the patellar (kneecap) ligament hold these bones in place.
Ligaments are strong, dense structures consisting of connective tissue that connect the ends of two bones across a joint. The function of ligaments is to stabilize a joint. The CCL plays a critical role in stabilizing the stifle (known as the knee in humans) against front-to-back forces. It prevents the tibia from shifting in front of the femur, controls excessive internal rotation of the joint and hyperextension, and is the structure most commonly injured. In fact, more than 600,000 dogs in the U.S. have surgery for this problem every year.
The top of the tibia that is in contact with the bottom of the femur is angled and sloped toward the back of a dog’s leg. When the CCL is torn, weight-bearing movement causes the femur bone to slide down this slope. Not only is this painful, but also causes the stifle to “give out” during weight-bearing. As the femur slides down the slope of the tibia, the meniscal cartilage—a cushion between the bones that acts as a shock absorber may be crushed. In about 50% of the dogs with CCL injuries, the meniscal cartilage has been injured as well. This type of injury is often accompanied by a “click” that can be heard when a dog walks.
When the CCL is weakened or torn, the most significant long-term change in the joint is the development of arthritis. All joints with instability will develop arthritis; however the severity and the effect of the arthritis will vary from dog to dog. Most dogs with a complete CCL tear show an immediate onset of lameness. While there may be some initial improvement over several days, there usually is a dramatic decline in limb function over time. There is no benefit gained from taking a “wait and see” approach. Stabilization of the joint soon after the injury has occurred is recommended.
In small dogs, nylon bands can be used to tighten the knee, however, this technique usually is not consistently effective in large breeds. There are two main types of surgery that are recommended for medium and large breed dogs that have CCL tears: the tibial tuberosity advancement (TTA) and the tibial plateau leveling osteotomy (TPLO). The TTA is a somewhat less invasive surgery and gives similar results to the TPLO. Dogs that receive the TTA procedure will recover quicker initially, however, by 4 months after surgery both procedures have similar outcomes.
The TTA procedure should not be used in dogs that have a steep tibial plateau, therefore your dog’s surgeon will make a decision which procedure is the best option for your companion. The TTA procedure involves making a cut in the front part of the tibia bone (tibial tuberosity) and advancing this portion of bone forward in order to realign the patellar ligament so that the abnormal sliding movement within the knee joint is eliminated. A specialized bone spacer, plate and screws are used to secure the bone in place. Bone graft is collected from the top of the tibia and placed in the gap in the bone to stimulate healing.
Biomechanics of the TTA
Now this will seem complicated when you look at the forces that are applied to the knee, but let me try to explain. There are opposing forces that affect the stability of the knee. The forces that come from the patellar ligament (from the pull of the quadriceps muscles), Fq, oppose the other forces applied (Fn and Ft). Because the patellar ligament is angled greater than 90 degrees to the top of the tibial slope (dashed line), there is a resultant shear force that causes the tibia bone to slide forward with weight-bearing; this force is normally neutralized by the cranial cruciate ligament. However, when the cruciate ligament is torn, this force causes the knee "give out" with every weight-bearing stride. After the TTA procedure has been completed, the angle of the patellar ligament approaches 90 degrees to the tibial slope and the opposing forces become cancelled, thus the tibia bone remains in place when weight is placed on the limb.
Aftercare and Results
After surgery, you can continue to give your pet a prescribed pain reliever to minimize discomfort. It’s also extremely important to limit your dog’s activity and exercise level during this post-operative period. Rehabilitation exercises can be done at your home or if you choose, by professionally trained therapists at an animal rehabilitation center. Rehabilitation therapy should be continued until your dog is bearing weight well on the operated limb (typically 8 weeks after surgery). Detailed instructions will be given to you after the surgery.
The healing process will be monitored by the surgeon with two follow-up exams. The first is scheduled at two weeks after the surgery and the second is at eight weeks after the surgery. By 8 weeks after surgery, the bone will be healed together. By 16 weeks after surgery, most dogs are fully weight-bearing on the operated limb, and exercise restrictions can be lifted at this time.
Complications are possible following TTA surgery; however, as the surgeon performs more and more of these procedures the complication rate also will decrease, but will not be totally eliminated. Anesthetic reactions are uncommon and rarely result in mortality under the care of trained specialists. Although infection may develop in the surgical site, this is uncommon, as strict sterile technique is used during the surgery. If your dog is receiving medications such as chemotherapy or steroids, the bone may not heal well, therefore it is imperative that you inform the surgeon prior to surgery that your dog is receiving these medications. Over activity in the postop period may also result in poor bone healing, loosening of the screws or breakage of the implant. In addition, if your dog falls, the tibia may fracture. Arthritis (bone spurs) is usually present at the time of diagnosis of a cruciate ligament rupture and likely will progress regardless of surgical procedure performed. At this time (Jan 2008) there is no report that demonstrates that the TTA procedure will slow the progression of arthritis. If the arthritis progresses, medications can be used to help relieve these signs. Reports indicate that there is about a 9 to 10% risk of developing a meniscal tear after TTA surgery (another report demonstrated greater than 20% meniscal tears), therefore most surgeons perform a meniscal release at the time of the surgery to prevent this complication. In comparison, only about 2% of TPLO cases develop a meniscal tear after surgery (with no meniscal release being performed). If the patient develops an infection in the surgical site and the implants need to be removed it can be a total nightmare for the surgeon to remove the implants. The cage that is frequently embeded in the bone will require drilling of the bone to remove it.
The TTA and TPLO procedures offer multiple benefits in comparison to older techniques which include: faster recovery, earlier use of the limb after surgery, better chance to return to full activity, and better range of motion of the joint. The TTA and TPLO procedures are currently the best methods available for stabilizing a dog’s knee. At the time of this writing (Jan 2008), no study demonstrated that working dogs receiving the TTA procedure will return to their peak athletic performance. Until supportive data comes out, I still recommend the TPLO surgery for athletes (agility, hunting, police dogs etc). In addition, I would not recommend this procedure for show dogs for two reasons: first, the tibial crest protrudes more, therefore a short-coated dog will have a visible difference in the appearance of the operated limb; second, following TTA surgery, the dog may walk with the stifle in a more flexed angle. Overall, the TTA appears to be a good treatment option for dogs that have ruptured the cranial cruciate ligament.
- Hoffman DE, Miller JM, Ober CP, et al. Tibial tuberosity advancement in 65 canine stifles. Vet Comp Orthop Traumatol 19:219-227, 2006
- Lafaver S, Miller NA, Stubbs WP, et al. Tibial Tuberosity Advancement (TTA) for stabilization of the canine cranial cruciate ligament deficient stifle joint: Surgical technique, early results and complications in 101 dogs. Vet Surg 36:573-586, 2007
- Apelt D, Kowaleski MP, Boudrieau RJ. Effect of tibial tuberosity advancement on cranial tibial subluxation in canine cranial cruciate-deficient stifle joints: an in vitro experimental study. Vet Surg 36:170-177, 2007
- Miller J, Shires P, Lanz O, et al. Effect of 9 mm tibial tuberosity advancement on cranial tibial translation in the canine cranial cruciate ligament-deficient stifle. Vet Surg 36:335-340, 2007
- Boudrieau RJ. Tibial Tuberosity Advancement (TTA): Present Evidence. Proceedings of Annual Conference of the American Chapter of Veterinary Surgeons, October 17-21, 2007; p 312
- Maquet P. Advancement of the tibial tuberosity. Clin Orthop Relat Res. Mar-Apr:225-30, 1976
- Karlsson J, Lansinger O, Sward L. Anterior advancement of the tibial tuberosity in the treatment of the patellofemoral pain syndrome. Arch Orthop Trauma Surg. 103:392-395, 1985
- Karlsson J, Sward L, Lansinger O. Bad results after anterior advancement of the tibial tubercle for patello-femoral pain syndrome. Arch Orthop Trauma Surg. 111:195-197, 1992
- Cheng CK, Yao NK, Liu HC. Surgery simulation analysis of anterior advancement of the tibial tuberosity. Clin Biomech (Bristol, Avon). 10:115-121, 1995
- Montavon PM, Damur DM, Tepic S. Advancement of the tibial tuberosity for the treatment of cranial cruciate deficient canine stifle. 1st World Orth Vet Congress 2002; 152
- Montavon PM, Damur DM, Tepic S. Tibial tuberosity advancement (TTA) for the treatment of cranial cruciate disease in dogs: evidence, technique and initial clinical results. 12th ESVOT Congress 2004: 254-255
- Elkins AD. A retrospective study evaluating the degree of degenerative joint disease in stifle of dogs following surgical repair of anterior cruciate ligament rupture. J Am Animal Hosp Assoc. 27:533-539, 1991
- Vasseur PB, Berry CR. Progression of stifle osteoarthritis following reconstruction of the cranial cruciate ligament in 21 dogs. J Am Anim Hosp Assoc. 28:129-136, 1992
- Arnoczky SP, Marshall JL. The cruciate ligaments of the canine stifle: an anatomical and functional analysis. AM J Vet Res. 38:1807-1814, 1977
- Bruce WJ, Rose A, Tuke J, et al. Evaluation of the triple tibial osteotomy. A new technique for the management of the canine cruciate-deficient stifle. Vet Comp Orthop Traumatol. 20:159-168, 2007
- Fitzpatrick NM, Yeadon R, Kowaleski MP. Tibial tuberosity transposition-advancement for treatment of medial patellar luxation and concomitant cranial cruciate ligament disease in the dog. Abstract, Annual American Chapter of Veterinary Surgeons Conference, 2007.
Frequently Asked Questions After Surgery
When should my dog have the first bowel movement after surgery?
- Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
- Reasons that a dog will not have regular bowel movements after surgery include:
- The dog has been fasted prior to surgery
- Dogs do not eat well during the hospital stay
- They frequently do not eat well when they go home
- They are fed highly digestible food that produces little stool
- Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
- If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
- Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable
My pet had surgery and will not eat. What can be done?
- Most pets will not eat their regular dog food after surgery, especially if it is kibble.
- Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source. The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked). The carbohydrate can be pasta, potato or white rice.
- Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
- Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
- Try Hill's A/D diet available at most veterinary hospitals
- Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
- Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
- Remember that most pets will not eat the first day or two after they get home from surgery
- Offer smelly foods that contain fish such as tuna or smelly cat foods
- Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
- Hand feeding: with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
- Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
- Some cats will only eat dry food, try kibble if your cat normally has been fed that food
- Petting and stroking your cat frequently will help to stimulate appetite
- Remember that most pets will not eat the first day or two after they get home from surgery
- Appetite stimulants such as cyproheptadine may be helpful
- If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop
My pet is vomiting. What can be done?
- The first thing for you to discern is whether your pet is vomiting or regurgitating. Both will result in fluid or food being brought up. Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus. Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled. Usually the regurgited material will be clear or brown colored fluid.
- Next is to identify the cause of the vomiting or regurgitation.
- Causes and treatment of vomiting after surgery
- When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
- Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery. In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart. Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to. The antibiotic in some cases may be changed to a different one, or may be discontinued.
- Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days.
- An uncommon cause of vomiting after surgery is internal organ failure. Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
- If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present. Do not ignore this sign.
- Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days. In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days. Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats. You should always consult a veterinary healthcare professional before administering medication.
- Causes and treatment of regurgitation after surgery
- The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia. Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis. This results in poor motility of the esophagus, therefore water and food will accumulate in this structure. In most cases, esphagitis is self-eliminating and will resolve within two or three days.
- If the esophagitis is severe the esophagus may develop one or more strictures. A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week. This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope). If an esophageal stricture is chronic surgery is needed.
- Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other). Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.
How do I know that my dog is in pain following surgery?
- Signs of pain include
- biting if you get near the surgical site
- grimacing (lips are pulled back and the the dog looks anxious)
- tragic facial expression
- restlessness and unable to sleep; pacing
- if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
- the worst pain will be for the first 2 to 3 days after surgery
What can I do to control my dog's pain?
- Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
- Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
- If an orthopedic surgery has been done cold packing the surgical site may be helpful
- A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack. An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern. Cooling the surgical site helps to numb the area.
How do I know that my cat is in pain following surgery?
- Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
- Signs of pain in a cat include the following:
- biting if you get near the surgical site
- growling or deep cry
- not wanting to eat
- hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)
What can be done for pain at home for my cat?
- Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
- Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
- Anti-inflammatories can be used, but the dose is much less than dogs
Is it okay for my pet to lick the incision?
- If a dog licks the incision, the healing process may be delayed.
- Licking can remove stitches and cause the incision to open
- Licking can become a severe habit that is difficult to break
- Licking can cause infection as the mouth has many bacteria
- Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
- To stop your pet from licking the following can be tried:
- Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
- Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
- A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
- A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
- Bitter apple can be applied around the incision; many dogs will continue to lick after application of this topical
- Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
- Antipsychotic medication in some cases is needed