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If your dog has suddenly come up lame on a back leg, start with one question. Does this need to be seen today? A dog who won't put the foot down at all, or who yelped and hasn't been right since, should be examined the same day. A mild limp that's still weight-bearing can wait 24 hours of strict rest to see which way it goes.
Key Takeaways
Come in today if: your dog won't put the foot down at all, the leg is hanging at an odd angle, there's obvious swelling, both back legs are weak or wobbly, your dog can't get up, or they're crying when they move. Non-weight-bearing lameness is painful and it's almost always structural. Book online or call (519) 896-0532.
You won't get a diagnosis from the driveway, and I wouldn't want you to try. What you can do is notice the pattern, because the pattern is most of what I'm working from when you walk in.
| What you're seeing | Most likely | What I'd do |
|---|---|---|
| Toe-touching on one back leg, came on fast, medium or large dog | Cruciate rupture | Book this week. Rest in the meantime, no stairs or running. |
| Mild limp after a hard play session, still bearing weight | Strain or sprain | Strict rest for 24 to 48 hours. If it isn't clearly better, book. |
| Both back legs weak or wobbly, knuckling, sore back | Disc disease | Same day. Spinal cases are time-sensitive. |
| Sudden after a fall or a car, leg held at an odd angle | Fracture or dislocation | Emergency. Don't splint it yourself, just keep them still. |
| Shortened stride behind, worse after exercise and on rising | Iliopsoas injury | Book. Rest and rehab, not surgery. |
| Limp worsening over weeks, firm swelling over the bone | Needs x-rays | Book promptly. This is the pattern I don't want to sit on. |
Start here. It's the most common answer by a wide margin.
You'll hear it called an ACL because that's the human term, but in dogs it's the cranial cruciate ligament, or CCL. It sits inside the knee and stops the shin bone sliding forward under the thigh bone. When it tears, the joint loses its stability and every step becomes painful.
The part that surprises most owners is the timeline. This looks sudden, but the ligament has usually been fraying for months and the fetch session just finished it off.1
The classic picture is a toe-touching lameness that's there all the time and doesn't settle with a few days of rest. Larger breeds are over-represented, particularly Labradors, Rottweilers and Newfoundlands, and neutered and female dogs are more commonly affected.2
I diagnose it by feeling for cranial drawer or tibial thrust, which is the shin bone shifting forward when I load the joint.1,2 Tense dogs often need sedation before that's reliable, so don't be surprised if I suggest it. About half of these knees also have a torn meniscus by the time we get in there.
Surgery is the recommendation for most dogs, and osteotomy procedures like TPLO are now the standard for medium and large breeds.2 Over 80% of dogs get good to excellent limb function afterward.2 There's a full walkthrough of the procedures, recovery and what it costs on our dog ACL and cruciate repair page.
Plan for one more thing. If one knee has gone, there's a 40% to 60% chance the other follows within a year or two.1 Keeping your dog lean is the single best thing you can do about that.
This is the one you want it to be.
A strain is a muscle or tendon injury. A sprain is a ligament injury. Either one gives you a sore, swollen, inflamed area and a dog who's reluctant to load the leg.
What separates a strain from everything else on this list is that it gets better. Give it 24 to 48 hours of real rest, meaning leash walks to the bathroom and nothing else, and you should see clear improvement. No stairs, no couch, no fetch.
If it's the same or worse after two days, it isn't a simple sprain and I'd want to see them. Watch out for the other pattern too: improves nicely, then relapses the moment your dog runs again. That's how partial cruciate tears behave.
Pain control helps, but it has to be a dog-specific anti-inflammatory like carprofen at a dose I've worked out for your dog's weight and kidney values.
Often this isn't really a limp at all, which is why it's worth knowing the difference.
The discs between the vertebrae act as cushions. When one herniates, it presses on the spinal cord or a nerve root, and what you get is weakness and wobbliness in both back legs rather than lameness in one.3 Dogs drag their toes or knuckle over. Their back is sore to touch. They're reluctant to jump or take stairs.
A disc pressing to one side can produce a genuine one-legged lameness, so it does belong in this list. But if both back legs are involved, treat it as more urgent than a limp, not less.
Breed is the strongest clue you have. Disc disease has a lifetime prevalence of around 3.5% across dogs, but it concentrates hard in chondrodystrophic breeds: Dachshunds, French Bulldogs, Beagles, Shih Tzus, Lhasa Apsos and Pekingese. Miniature Dachshunds carry roughly a 20% lifetime risk.3
Mild cases can be managed with strict crate rest and medication. Dogs losing function need imaging and often surgery, and the sooner that happens the better the odds.
You'll know this one when you see it.
The leg is held at an angle that isn't right, there's swelling, and the dog is in real distress. It takes trauma, but not necessarily dramatic trauma. Small dogs fracture legs jumping off furniture.
Don't try to splint or straighten anything at home. You'll cause more pain and you can turn a clean fracture into a worse one. Confine your dog somewhere small and safe, support them with a towel sling under the belly if they have to move, and come straight in.
Hips are the joint that most often comes out in dogs, and there's more detail on how those are put back and kept in on our post about hip dislocation in dogs.
This is the one that gets missed.
The iliopsoas runs along the underside of the spine into the top of the femur, and it flexes the hip and brings the leg forward.4 It gets injured through overuse and hyperextension: repetitive fetch, agility work, or a leg sliding out from under a dog on a slippery floor.
The tell is a shortened stride behind. Not a dramatic limp, just a leg that isn't reaching as far, worse after exercise and worse getting up off the floor. On exam there's pain when I extend the hip, particularly with the leg rotated inward.4
Ultrasound in experienced hands is the practical way to confirm it. CT and MRI work too but cost considerably more.4
Treatment is rest, pain control and a proper rehabilitation program, usually four to twelve weeks.4 Rushing back is how these become chronic. We go into the detail in our post on iliopsoas muscle injury in dogs.
It's uncommon compared to the other causes. I include it because the pattern is recognisable and because catching it early changes the conversation.
Bone cancer causes lameness that gets steadily worse and doesn't respond to rest. There's often firm swelling over the affected bone. In the back leg it favours the area around the knee, at the lower femur and upper tibia. Sometimes the first sign is a sudden non-weight-bearing lameness because the weakened bone has fractured.5
Large and tall breeds carry the most risk, though dogs under 15 kg are still affected.5 Diagnosis starts with x-rays of the limb and chest, then a needle sample or biopsy.5
I'll be straight about the outlook. With amputation alone, median survival is typically under five months.6 Adding chemotherapy after surgery extends that to somewhere in the range of eight months to a year.5,6 Those are hard numbers to hear. What I'd want you to know is that pain control for these dogs is genuinely good, and plenty of families get real quality time. Our post on osteosarcoma in dogs covers the decisions in more depth.
I'll watch your dog walk first, before I touch anything. Gait tells me more than palpation does.
Then I work the whole leg from toes to hip, comparing it against the other side, and I check the spine and the neurological responses. That's how the disc cases separate out from the orthopedic ones.
For a suspected cruciate, I'm testing for drawer and tibial thrust. If your dog is tense, I'll suggest sedation, because a strong dog can splint a knee well enough to hide the movement I'm looking for.1
X-rays come next if I need them, either to look at the joint before surgery or to look at the bone itself.
Bring your dog in hungry if you can. If sedation or x-rays turn out to be the right call, an empty stomach means we can do it that visit instead of booking you back.
Most sudden hind leg lameness is fixable, and the dogs who do best are the ones I see in the first few days. Three weeks of hoping is the version that goes badly. If your dog is limping and you're in Kitchener, Waterloo or Cambridge, book an appointment or call us at (519) 896-0532.
The clearest line is weight-bearing. If your dog won't put the foot down at all, the leg is held at an odd angle, there's obvious swelling, or both back legs are weak and wobbly, that's a same-day visit. If your dog is still using the leg and is otherwise bright and eating, 24 to 48 hours of strict rest is a reasonable trial before booking.
The ligament itself doesn't heal. Some small dogs stabilise well enough with strict rest, weight loss and pain control that they end up comfortable, but the knee stays unstable and arthritis sets in faster. For medium and large dogs I'd recommend surgery, and most get good to excellent function afterward. Either way, 40% to 60% of dogs go on to rupture the other side, so keeping your dog lean matters more than owners expect.
Dogs are poor at showing pain in ways we recognise. Yelping is the exception, not the rule. The limp is itself the pain signal, and a dog who is wagging, eating and meeting you at the door can still have a torn ligament. Don't use their mood to rule anything out.
Ibuprofen, naproxen and acetaminophen are all dangerous to dogs, and human anti-inflammatories are among the most common poisonings reported in pets. Dogs get stomach ulcers and kidney injury from them far more readily than we do. There are good dog-specific anti-inflammatories, but they need a dose worked out for your dog's weight, and I'd want kidney values first.
Two days, and it has to be real rest. One room, leash walks for the bathroom only, no stairs, no couch, no fetch. If the limp is clearly better after 48 hours, keep resting and bring activity back slowly over the following week. If it's the same or worse, book an exam. Book one too if your dog improves and then relapses the moment they run again, because that's how partial cruciate tears behave.
No. Cruciate rupture, the most common cause I see, often has no swelling you'd notice from the outside. The joint fills with fluid internally and the thickening around it builds over weeks. Absence of swelling is not reassurance.
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