Why does my dog keep hopping or skipping on one back leg?

An intermittent skip, where a dog picks up a hind leg for a step or two and then walks normally again, is the classic sign of patellar luxation, a condition in which the kneecap slides out of the femoral groove it's supposed to glide in. The American College of Veterinary Surgeons notes that medial patellar luxation is one of the most common orthopedic conditions in dogs, seen frequently in small breeds such as Yorkshire Terriers, Pomeranians, and Chihuahuas, though it also occurs in large breeds (American College of Veterinary Surgeons, 2023). Luxations are graded I through IV based on how easily the kneecap dislocates and whether it returns to place on its own, and low-grade cases can go unnoticed for years before becoming more frequent.

A dog that stops mid-stride, cries out once, and then won't put weight on a back leg is more likely dealing with a cranial cruciate ligament (CCL) injury, the canine equivalent of an ACL tear. Cornell University's Riney Canine Health Center identifies CCL rupture as the most common cause of hind-limb lameness and knee osteoarthritis in dogs, and unlike a human ACL tear from one violent twist, the canine version often results from gradual ligament degeneration that culminates in a sudden full tear during ordinary activity like jumping off a couch (Cornell Riney Canine Health Center, 2022).

What actually causes a dog's kneecap to slip out of place?

Patellar luxation is largely a structural problem: a shallow or misshapen femoral groove, misaligned thigh muscles, or a bowed lower leg bone can all pull the kneecap toward the inside (or, less commonly, outside) of the joint. The Orthopedic Foundation for Animals notes that the condition has a strong hereditary component in toy and small breeds, which is why many breed clubs recommend evaluating breeding stock before pairing dogs (Orthopedic Foundation for Animals, n.d.). Trauma, such as a fall or being struck by a car, can also cause a previously normal kneecap to luxate for the first time, particularly in larger dogs.

Cruciate ligament disease has a murkier but increasingly well-studied cause. Research summarized by the AKC Canine Health Foundation points to a combination of genetics, obesity, conformation (especially a steep tibial plateau angle), and chronic low-grade inflammation within the joint that weakens the ligament over months or years before it finally ruptures (AKC Canine Health Foundation, 2021). Breeds like Labrador Retrievers, Rottweilers, and Newfoundlands are overrepresented, and a dog that tears one knee's ligament has a substantially elevated chance of rupturing the other knee's ligament within a couple of years, according to veterinary orthopedic literature cited by Cornell's canine health program (Cornell Riney Canine Health Center, 2022).

How does a vet figure out which knee problem my dog has?

Diagnosis starts with a hands-on orthopedic exam. For patellar luxation, the veterinarian manually pushes on the kneecap while flexing and extending the leg to see how easily it pops out of the groove and grades it on the standard I-IV scale described by the American College of Veterinary Surgeons (American College of Veterinary Surgeons, 2023). For suspected cruciate injury, the vet performs a "cranial drawer test," checking whether the shin bone slides forward abnormally relative to the thigh bone, and a "tibial compression test" that mimics weight-bearing forces on the joint.

X-rays are usually taken regardless of which condition is suspected, both to rule out fractures or bone tumors and to look for joint effusion, a fat pad sign, and early arthritic changes that support a cruciate diagnosis. In dogs with partial ligament tears or subtle findings, some specialty hospitals use advanced imaging like MRI or arthroscopy to confirm the diagnosis before recommending surgery, a step the American Animal Hospital Association's orthopedic guidelines support for uncertain cases (American Animal Hospital Association, 2021).

Does a dog with a bad knee actually need surgery, or can it heal on its own?

For cruciate ligament tears, surgery is the standard recommendation for medium and large dogs because the canine knee has almost no capacity to stabilize itself once the ligament is fully torn. Common procedures include tibial plateau leveling osteotomy (TPLO) and tibial tuberosity advancement (TTA), both of which change the biomechanics of the joint rather than simply replacing the torn ligament, and Cornell's veterinary orthopedic surgeons report that most dogs regain good to excellent limb function within three to six months after TPLO (Cornell Riney Canine Health Center, 2022). Small dogs under about 10 kg sometimes do reasonably well with a simpler lateral suture technique or even strict rest and physical rehabilitation, but outcomes are inconsistent without surgical stabilization.

Patellar luxation treatment depends heavily on grade. The American College of Veterinary Surgeons notes that Grade I luxations that cause no lameness often just need monitoring, while Grade II through IV cases causing persistent lameness typically require surgery to deepen the femoral groove, realign the tibial crest, and tighten the joint capsule (American College of Veterinary Surgeons, 2023). Left uncorrected, chronic luxation accelerates cartilage wear and increases the risk of a secondary cruciate ligament tear in the same knee.

What can I do at home to help my dog's knee recover or manage a chronic luxation?

Weight management is the single most modifiable factor in canine knee health. The World Small Animal Veterinary Association's global nutrition guidelines note that even modest excess body weight increases joint loading forces and inflammatory markers that worsen osteoarthritis progression, so keeping a dog at an ideal body condition score reduces strain on a healing or luxating knee (World Small Animal Veterinary Association, 2021). After surgery, controlled leash walks, hydrotherapy, and formal canine rehabilitation protocols — often supervised by a certified canine rehabilitation practitioner — are credited by orthopedic surgeons with speeding return to function and reducing muscle atrophy.

For dogs managing a low-grade luxation without surgery, or recovering from a cruciate repair, non-slip flooring, ramps instead of stairs, and avoiding repetitive jumping on and off furniture all reduce the shearing forces that aggravate the joint. Veterinarians frequently prescribe joint supplements containing glucosamine and omega-3 fatty acids alongside NSAIDs for pain and inflammation control, though the American Animal Hospital Association's chronic pain guidelines emphasize that supplements support but don't replace surgical correction when a knee is structurally unstable (American Animal Hospital Association, 2021).

What's the long-term outlook for a dog with chronic knee problems?

Most dogs that undergo appropriate surgical correction for either condition go on to live active, comfortable lives, though some degree of osteoarthritis in the affected joint is nearly universal over time. Cornell's veterinary researchers note that dogs treated surgically for cruciate rupture generally show better long-term limb function and less progression of arthritis than dogs managed conservatively, particularly in dogs over 15 kg (Cornell Riney Canine Health Center, 2022). Regular weight checks, joint-friendly exercise like swimming, and periodic veterinary recheck exams help catch early arthritic flare-ups before they become debilitating.

Dogs with a genetic predisposition to patellar luxation, especially toy breeds, may need lifelong monitoring even after successful surgery, since the underlying skeletal conformation that caused the initial luxation doesn't fully disappear. The Orthopedic Foundation for Animals recommends that affected dogs not be used for breeding, since the trait is heritable and passing it on perpetuates the problem in future litters (Orthopedic Foundation for Animals, n.d.).

Which dog breeds are most at risk for knee problems, and can screening catch it early?

Toy and small breeds top the list for patellar luxation, with the Orthopedic Foundation for Animals reporting particularly high rates in Yorkshire Terriers, Chihuahuas, Pomeranians, and Boston Terriers, while large athletic breeds like Labrador Retrievers, Golden Retrievers, Rottweilers, and Newfoundlands are overrepresented for cruciate ligament disease (Orthopedic Foundation for Animals, n.d.). Because both conditions have hereditary components, the OFA offers a standardized patellar luxation screening exam that breeders can use to certify breeding stock before pairing dogs, reducing the odds of passing the trait to puppies.

Annual wellness exams that include a hands-on orthopedic check are the most practical early-detection tool for pet owners, since a veterinarian can often feel a mild kneecap laxity or early cruciate instability before a dog shows obvious lameness. The American Animal Hospital Association recommends that overweight or predisposed breeds get their knees specifically assessed at routine checkups, since catching a Grade I or II luxation early allows for monitoring and lifestyle adjustments before it progresses to a surgical case (American Animal Hospital Association, 2021).