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ACL Injury

ACL Injury

What is an ACL injury? 

The anterior cruciate ligament (ACL) or cranial cruciate ligament (CCL) is one of the most main stabilizing structures of the knee (stifle) joint in the hindlimbs of dogs. The ACL is a rope-like structure inside the joint that acts as a static (constant) stabilizer of the knee, preventing abnormal “slipping” of the two bones of the knee joint, the femur and tibia. Its main job is to hold the femur and tibia in proper alignment during all forms of activity.

Deficiency of the ACL is the most common orthopedic problem in dogs and inevitably results in degenerative joint disease (arthritis) in the knee joint. It is often referred to as a disease because it is typically the result of a degenerative process in dogs, rather than the from athletic injury or trauma. Although it is often noticed after running, playing, or jumping, the disease process has usually already been present for weeks to months when symptoms occur. Illustrating this point, 50 – 70% of dogs that rupture an ACL will rupture the ACL on the other leg.

One of the most important issues with ACL injury has to do with the medial meniscus. The medial and lateral menisci are “cushions” of cartilage positioned on top of the tibia, cushioning the force from the femur. When the ACL ruptures, a large amount of stress is placed on the medial meniscus, and it is often damaged. The damaged and unstable meniscus is particularly uncomfortable, and cleaning the damaged part of the meniscus is an important part of ACL surgery. It is possible for meniscus damage to progress even after surgery. As many as 9% of dogs have continued meniscus problems after surgery.

We are increasingly using “balanced anesthesia”, which incorporates pain management through multiple mechanisms. Multiple drugs at smaller doses are more effective and safer than a single drug at a big dose. Additionally, local anesthesia (local block) can help reduce the amount of general anesthesia needed. MPH uses a local anesthetic that can last up to three days!

This reduces the need for general anesthesia and post-op pain meds. It’s ideal for many surgery sites, and is even helpful in healing naturally occurring wounds. Risks are minimal, but can include irritation or infection at the surgery site. But this also helps reduce the risk of infection, by eliminating pain that may otherwise cause your pet to lick or traumatize an incision.


What are my treatment options?

ACL injury is not life threatening, and surgery is not absolutely necessary. Occasional dogs, especially very small dogs, can do OK with rest, pain medication, and physical therapy. In general, conventional wisdom is that dogs will have more significant arthritis without surgery. Success can be particularly slower if there is meniscal injury. Even with surgery, dogs will still develop arthritis, but less significant arthritis than without surgery. While there are many surgical options, there are 3 more common surgeries. There are no definitive studies showing one surgery to be better than another. Each surgery has its own set of pros and cons.


Tibial Plateau Leveling Osteotomy (TPLO) is generally considered to be the best “state of the art” surgery addressing the underlying reason why ACL injury is so common in dogs. This has to do with the alignment of the femur and tibia, changing the anatomy of the top of the tibia so that it no longer “slips” with pressure from the femur. It does not replace the function of the ACL, but instead makes the ACL unnecessary. A semicircular cut is made at the top of the tibia with a curved saw so that the tibial joint surface is “leveled out” to prevent forward slipping of the joint. A plate and screws are applied to stabilize the cut bone during healing. There is a variation of the TPLO called Tibial Tuberosity Advancement (TTA). The TTA is similar in concept, but the cut made in the tibia is different.


Lateral Suture Stabilization is historically the most common technique used to treat ACL injury in dogs. It is one of the “extracapsular” techniques which means the function of the ACL, which is inside the joint, is replaced by placing a suture outside the joint. The suture is placed around the fabella and through either the tibia or patellar ligament, providing a mostly soft tissue anchor for joint stabilization. 


Tightrope Stabilization was developed recently, and basically is less invasive than the TPLO, and provides more reliable stabilization than the Lateral Suture. This technique does not require cutting of bone like the TPLO, but instead uses small drill holes in the femur and tibia to pass a synthetic ligament-like biomaterial outside of the joint. The material is called FiberTape. It is a kevlar-like material that is used extensively in human orthopedic surgery. FiberTape is stronger and less prone to failure than typical materials used for the Lateral Suture. Placing the FiberTape through the holes in the bone provides bone-to-bone stabilization. Also, through very precise location of the anchor points, normal range of motion in the stifle can be retained.

What happens after surgery?

The recovery period is pretty similar for all three surgeries. We typically keep your dog in the hospital overnight, and send them home the next day. The first week is mostly making sure they are not painful, or chewing at their incision, then in the following weeks we start to focus on rehabilitation. You will need to restrict exercise for 8 weeks. This mostly includes keeping all activity on leash, with no running or jumping. We will want to recheck every 1-2 weeks through the first 2 months with the purpose of monitoring progression and guiding rehabilitation.


Complications can occur with any surgery. These include surgical infection, loosening of the stabilization material, and continued meniscus damage. These complications are essentially uncommon (5% or less). Even less commonly, stabilization material (suture, TightRope, and plates) can break, especially when the bone or surrounding soft tissues have not healed, or within the first 2-3 months. If the material breaks, typically more surgery is required to repair it. If a TPLO plate breaks, the result is significantly more devastating, requiring surgery to repair the cut bone. Lastly, any foreign material or arthritic joint is more prone to getting seated with bacteria in the future. This is not a surgical complication but it is a underlying predisposition.


The bottom line is that there is not one surgical option that is best for all circumstances. Some dogs do absolutely well with Lateral Suture (especially small, muscular dogs) and some dogs really need a TPLO (especially larger dogs that are more prone to arthritis problems). The TightRope is generally a good alternative for most dogs.

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