Dr. Christopher James Wood, DVM (Dist), MS, BSc
Diplomate, American College of Veterinary Surgeons (Small Animal)
Torn ACL?
1 / Why does a torn ACL matter?
The anterior cruciate ligament, known as the ACL, is a tough band inside your dog’s knee that works like a rope to stop the shin bone from sliding forward when your dog walks, runs, or jumps.
Small repeated strains, extra weight, and the steep slope of the top of the shin bone slowly fray the ligament’s fibers—just like an old rope that’s been tugged too many times—until it finally tears.
Once the ligament fails, the joint becomes unstable and the shin bone now slides forward when your dog walks, runs, or jumps. The sliding bones grind cartilage and pinch the meniscus—the knee’s shock-absorbing pad—causing pain, swelling, and early arthritis.
2 / What are the surgical options?
There are two main ways we can fix this knee problem.
One option uses a strong nylon suture placed around the joint to act like the torn ligament and holds the knee steady while scar tissue develops around the joint over time for lasting stability.
The other option involves carefully cutting the shin bone and changing its angle, which removes the sliding forces in the knee so it stays stable even without the ligament. Studies show that owners are more satisfied with the results of the bone-cutting surgery (1); dogs return to normal weight-bearing faster, and by one year after surgery, their leg function is the same as healthy dogs (2).
When a nylon suture is used, the goal is to place it at anchor points on the thigh and shin bones so they stay the same distance apart as the knee bends and straightens (isometric points). But in reality, the knee doesn’t just bend (it also rolls, slides, and rotates), for a total of 3,681 pairs of isometric points anchor spots (3).
In small-sized dogs only half of the knees treated with the suture method have a good or excellent outcome, and about one in three of these dogs need anti-inflammatory medicine at least once a month (most needed it daily) (4). In medium- to large-sized dogs , about two out of every five will still need anti-inflammatory medication long-term after this type of surgery (5).
3 / What does "TPLO" stand for?
The most common "bone cutting" knee surgery for a torn ligament in dogs is called a Tibial Plateau Leveling Osteotomy (TPLO).
Osteotomy = a precise, planned bone cut
Tibia = the shin bone
Plateau = naturally sloped top of the tibia
Leveling = rotate the cut top to flatten that slope
4 / How does a TPLO fix this?
The TPLO surgery does not not fix the torn ligament, it stops the shin bone sliding forward by changing the shape of the tibia. We cut and rotate the top of the shin bone so it goes from a steep “slide” (about 20–30°) to a nearly flat “floor” (about 3–7°).
With the surface now level, the dog’s weight pushes straight down instead of downhill, and the shin bone no longer tries to thrust forward, so the knee stays lined up even without an intact cruciate
If the sloped top of the tibia is too steep (>34°), correction to a nearly flat “floor” (about 3–7°) can require an excessive rotation with a normal TPLO that has a higher complication rate (6). In these cases we level the tibial plateau by cutting a wedge out of the bone instead, a 'Wedge TPLO'
5 / Don't think of it as "ligament repair"
Think of a TPLO as a bone repair—similar to treating a fracture—because the stability comes from the new bone position and the plate, not from fixing the torn ligament.
A strong metal plate and screws lock the rotated piece in place. Over a few months, new bone grows across the cut, making the change permanent.
7 / When can my dog do stairs?
If you have one or two steps out to the yard you may help your dog with the support of a sling, again, slowly, one leg at a time. Ideally however you use a ramp or if your dog is <15kg you carry them over any steps.
Flights of stairs are not formally introduced until week 8, however not all recoveries are the same, so some dogs may be able to start stairs at week 6. Here they are used as a strength-building exercise. The goal is to go SLOWLY and have your dog climb each step one leg at a time. If your dog is bunny hoppping (both hind legs together), they are going too fast.
8 / What does the recovery look like?
Weeks 0-2 – Strict crate rest
Weeks 3-7 – Leash walks with progressive strengthening and balance exercises
Weeks 8-12 – X-rays confirm bone healing. Unlimited leash walks with trotting, hills, and light play.
Months 4-6 – We clear for flat-out sprints or sharp turns in public parks.
Click the images below to browse photos and videos of patients during different stages of their recovery.
For an initial assessment, and a tailored rehab plan, please contact Carrie Smith at crsmobilerehab@gmail.com or visit crsmobilerehab.com to book an appointment
9 / What are the common complications?
Most TPLO complications fall into two groups
1. Implant-related (the metal plate and screws inside)
2. Incision-related (the skin and stitches outside)
Implant-related (metal plate and screws inside)
Remember that the TPLO is a bone repair, like fixing a broken bone, not a repair of the torn ligament. The plate and screws act like an internal scaffold while the bone heals, and if too much force goes through the leg too soon (specifically the first 6 weeks), that strong metal plate and screws can bend/break or pull loose.
Please watch the video below to see how a TPLO plate and screws ‘pull out’ of an apple. Bones are obviously stronger than apples, but the idea is the same.
The simple, but not easy solution:
No stairs, running, jumping, or off-leash activity
Incision-related (the skin and stitches outside)
An infection of the skin incision over a TPLO is reported in 1 in 12 TPLOs, and ~2/3 of those infections end in plate explantation if they are not treated promptly.
Treating a deep infection often approaches the original cost of the TPLO; culture-guided antibiotics for 6-8 weeks, additional rechecks and radiographs, and a second surgery to remove the plate and screws once the bone has healed
The reason for this is that bacteria still to metal and make a slimy shield called a biofilm. Think of it like tooth plaque that protects them, Metal doesn’t have a blood supply, so antibiotics can’t reach the bacteria. That means antibiotics only control the infection until the bone is healed, and we can remove the metal plate and screws to get rid of the problem. Most complications stop at “remove the plate” but in extreme cases, amputation or even euthanasia can occur.
The simple, but not easy solution:
E-Collar/Cone on at all times
Check the skin incision at least once a day
