HELP! My dog is limping, now what?
Lameness in dogs is a common occurrence. It can be a sudden onset, or more gradual starting subtly (“Did he just limp?”) and progressing to unmistakable lameness, perhaps even holding the limb up completely . There are several reasons for lameness in dogs, so the first thing you should do is have your pup evaluated by your veterinarian. They will perform and exam and try to determine the root cause of the lameness. Radiographs (x-rays) may be recommended. If the cause of the lameness isn’t an urgent diagnoses (fracture, fibrocartilagenous embolism, herniated disc, etc.) or if the cause is unable to be determined, you may be prescribed rest and non-steroidal anti-inflammatories for 4-6 weeks with a re-check if symptoms don’t resolve.
This blog series is going to discuss the most common diagnoses that would benefit from physical therapy, but they all often start with a lameness or altered gait pattern. Today I am going to discuss the most common reason for hind limb lameness in dogs-cranial cruciate ligament (CCL) tears. The CCL in a dog’s stifle (that’s what a dog knee is called) is the same as the ACL, or anterior cruciate ligament, in human knees. The CCL and ACL perform the same functions:
Limits cranial (forward) tibial movement
Prevents hyperextension (the knee over straightening)
Prevents excessive internal (in toward the body) rotation
What does all this mean? To understand what the CCL does, we need to understand the anatomy of the stifle joint. This joint is comprised of four main bones, the femur (thigh bone), the tibia (large shin bone), the fibula (the smaller shin bone), and the patella (knee cap). There are the two ligaments (cranial and caudal cruciate ligaments) that stabilize the femur in relation to the tibia, and two menisci (medial and lateral or towards the inside and outside of the leg, respectively) which act as cushions between the femur and the tibia. The CCL is the main stabilizer of the knee joint. It originates on the back of the femur and inserts on the front of the tibia. This positioning helps limit how much forward movement the tibia has on the femur, and prevents hyperextension and excessive internal rotation of the knee joint. If the ligament ruptures completely, this stability is lost and the tibia moves forward relative to the femur. This excessive motion and shear often cause injury to the medial meniscus because it attaches to the tibia at the back of the joint. The lateral meniscus does not tend to get injured because it attaches to the femur so moves with femur. The menisci have little to no blood supply so do not heal if injured.
The CCL does not usually start out as a complete rupture, most often it is a chronic degenerative disease. There are three grades of CCL sprain:
Grade 1: stretching of fibers, pain noted on stifle extension, but no instability
Grade 2: partial tear, pain, instability often detected in flexion (bending) of the stifle and when non weight bearing on the limb
Grade 3: complete rupture, pain, and significant instability noted
What this means, is often a dog has a Grade 1 sprain, goes through rest and NSAIDs and gets better, but then goes on to have a partial tear down the line. First tearing only a few fibers, then a few more, etc. so it becomes a chronic degeneration.
How does a CCL injury present?
Lameness: may be a weight bearing lameness where they put the leg down, but don’t have full weight on it, or non weight bearing lameness where they hold the leg up completely and have no weight on it at all
Altered sit position: often the injured leg is held out to the side rather than being underneath them because it is uncomfortable to have the knee fully bent
In standing, you may see increased hip and stifle flexion (bent more), and increased hock (ankle) extension (straightening) to enable the foot to touch the floor
Joint effusion/swelling
Pain on extension of the knee (often the first sign of a cruciate issue)
If this is a chronic condition, there will be muscle atrophy in the limb from the decreased use/decreased weight bearing
There will be abnormal movement of the tibia on the femur (your veterinarian can test for this)
There may be a click heard with range of motion of the stifle which can indicate a meniscal tear, although there can be a tear and no click
The best option for correcting this injury is surgery which will improve function and reduce the progression of osteoarthritis. Surgery sooner rather than later is better because there is less repeated trauma to the tissues. There are many types of surgery, the most common being:
Extracapsular stabilization: a suture is placed to stabilize the knee temporarily and lays a pathway for scar tissue to form. Sometimes performed on smaller dogs, but over time it may loosen or pull out. Less expensive, but generally not great long term results with this method.
Tibial Osteotomies: TPLO, TTA, CBLO are the most common, but there are many forms of this type of surgery
The gold standard today is the TPLO or tibial plateau leveling osteotomy which cuts the tibia, rotates the bone, and stabilizes this new position with a plate and screws. This procedure changes the angle of tibia on the femur and therefore eliminates the instability caused by the ligament rupture.
To see a great video demonstrating the stifle anatomy and how the TPLO surgery is performed click here
Many veterinarian surgeons perform an arthroscopic surgery prior to the TPLO to inspect the meniscus, if it is torn, it will be removed, but if it is intact, it is left alone. A torn meniscus can be very painful!
After surgery, the dog will be on restricted activity for several weeks. The restricted activity does not mean no physical therapy! Physical therapy is very beneficial and very important after these surgeries to decrease pain and inflammation and improve strength and use of the limb, but it needs to be gradual and progressed carefully based on the dog’s progress. If there has been some time between the injury and the surgery, the dog often needs to learn to use the limb again since they may have adapted to a three legged gait for ease, speed, and comfort. Through a variety of progressive exercise, the dog learns to trust and use the limb again gradually and then can build up the muscle strength to return to normal use of the limb. It takes about 8 weeks for the bone to show signs of healing. Often at this point, you will have follow up x-rays to be sure that this is happening and if all looks good, you will be given the okay to advance activity. However, this also needs to be done gradually to prevent injury. Remember, the dog has been restricted for eight weeks or more. Just because the bone is healing doesn’t mean he should resume zoomies and rough play. He needs to work on building up activity gradually and should be back to full strength before being “let loose” completely. Soft tissue injuries are common if allowed to do too much too soon.
Sometimes however, surgery is not an option. In this case, conservative management of the ligament rupture is pursued. The body will naturally try to “fix” the rupture by laying down scar tissue over a period of many months to stabilize the joint. As amazing as the body is, this repair is not as stable as surgery. If the dog does too much he may tear the scar tissue and the remodeling has to begin again. Osteoarthritis will form more quickly and be more severe with conservative management. However, with the help of rest, medications, and physical therapy dogs are often able to recover to an adapted normal life.
Hopefully this has helped explain a little bit about cranial cruciate ligament ruptures. Stay tuned for next week’s blog: luxating patella!
References:
Millis, Darryl L. & Levine, David. (2014). Canine Rehabilitation and Physical Therapy (2nd edition), Elsevier
Zink, Chris & Van Dyke, Janet B. (2018). Canine Sports Medicine and Rehabilitation (2nd edition), WILEY Blackwell
TPLO info (2022 April 12) CCL Tears and How TPLO Surgery Works, https://www.youtube.com/watch?v=VsCq353sy14