The phone call almost always sounds the same. A working dog was fine yesterday, jumped off the back of the truck or turned hard after a ewe, and now it won’t put weight on a hind leg. The owner wants to know if it’s a sprain that’ll settle with a few days’ rest. Usually, it isn’t. Usually, it’s the cranial cruciate ligament, and the dog has just joined the single most common orthopaedic problem I see in athletic shepherds.
The frustrating part — the part owners struggle to accept — is that this almost never happens out of nowhere. The injury looks acute. The disease underneath it has been brewing for months.
This Is Not a Sprained Knee
In humans, a torn ACL is a trauma injury. A footballer plants a foot, twists, and snaps an otherwise healthy ligament. People assume the canine version works the same way. It mostly doesn’t.
In dogs, the cranial cruciate ligament usually fails through chronic degeneration. The ligament fibres weaken and fray over time until a fairly ordinary movement finishes them off. That’s why you’ll see a dog rupture a cruciate stepping off a kerb — the load wasn’t extreme, the ligament was already three-quarters gone. It also explains the single most important fact owners need to hear: if one knee has gone through degeneration, the other one is very likely on the same path. Studies consistently put the rate of rupture in the opposite knee at roughly 40–60% within 18 months to two years. When I diagnose one cruciate, I’m already counselling for the second.
This distinction matters practically. A genuine soft-tissue strain, like the iliopsoas and shoulder injuries I’ve written about in exercise-induced injuries in working shepherds, can genuinely recover with rest and controlled rehab. A ruptured cruciate will not knit back together. The ligament is inside the joint, bathed in joint fluid, with no blood supply to heal it. Resting the dog reduces the pain. It does not fix the knee.
How to Spot It
The textbook sign is sudden hind-limb lameness, but the presentation varies with how complete the tear is.
A full rupture gives you a dog that’s severely lame, often toe-touching or carrying the leg entirely. A partial tear is sneakier — intermittent lameness that flares after hard work and eases with rest, which owners and even some vets mistake for arthritis or a niggling strain. Over weeks it gets steadily worse rather than better. That trajectory is the tell.
The most useful thing you can do at home is the sit test. Watch how your dog sits. A dog with a painful cruciate doesn’t want to flex the knee fully, so it sits with the affected leg kicked out to the side rather than folded neatly underneath. If your shepherd has started sitting “sloppy” on one side, take it seriously.
In the consulting room I’m feeling for two things: joint swelling (a thickening on the inside of the knee called a medial buttress), and cranial drawer or tibial thrust — abnormal forward slide of the shin bone that confirms the ligament is no longer doing its job. A partial tear can have a stable-feeling drawer test, which is exactly why these get missed. Radiographs don’t show the ligament, but they show joint effusion and the early arthritis that confirms this has been going on a while.
The TPLO Decision, Honestly
Here’s where owners want a simple answer and I can’t give them one. There are two broad paths: surgery or conservative management. Let me be straight about both.
Surgery is the gold standard for a reason. The most common procedure now is the TPLO — tibial plateau levelling osteotomy. Rather than trying to replace the ligament, the surgeon cuts the top of the shin bone and rotates it to change the joint’s geometry, so the knee is stable under load without needing the cruciate at all. For a large, active herding dog, the biomechanics genuinely favour it. Recovery to soundness is faster and more complete than the alternatives, and most working dogs return to function. The downsides are real: it’s a major bone surgery, it costs (typically £3,000–£5,000 per knee in the UK), and there’s a recovery period that demands discipline.
Conservative management — strict rest, weight control, anti-inflammatories, physiotherapy and time — is not nothing, and it’s not a con. For a smaller, lighter, or older dog, or where surgery genuinely isn’t affordable, a meaningful proportion stabilise with scar tissue over three to six months. But I won’t pretend the outcomes match surgery in a 30-kilo working Malinois. The bigger and more athletic the dog, the more the scales tip toward surgery. The knee will develop arthritis either way; surgery slows that progression, conservative management lets it run.
If cost is the barrier, say so out loud to your vet. There are other surgical options — lateral suture techniques cost less and suit lighter dogs reasonably well — and being honest about budget gets you a better plan than quietly choosing nothing.
Recovery Is Where Surgeries Are Won or Lost
I’ve seen perfect TPLOs fail because the owner let the dog “have a little run” at week three. The bone takes around eight weeks to heal. During that window, restriction is everything: lead exercise only, no jumping, no stairs, no off-lead freedom, no playing with other dogs. It is genuinely harder to keep a recovering Border Collie quiet than to do the surgery.
Build the exercise back gradually under your surgeon’s protocol — short controlled lead walks lengthening week by week, then structured rehab. Keep the dog lean; every excess kilo loads that healing joint. Underwater treadmill work, where available, rebuilds the thigh muscle that wasted while the leg was sore.
And manage the long game. This joint has arthritis in its future whatever you choose, so the arthritis management strategies for older shepherds become part of life — as does keeping a close eye on the other knee. Because the genetics that gave you one degenerate cruciate, much like the inherited risk behind hip dysplasia in herding breeds, don’t stop at one joint.
The Bottom Line
A cruciate rupture in a working shepherd is rarely a freak accident — it’s degeneration that finally gave way, and the other knee is on notice. The TPLO isn’t the only answer, but for a large athletic dog it’s usually the one that gets the most leg back. Whatever you choose, decide deliberately, commit to the recovery, and watch the second knee. The dogs that do best are the ones whose owners understood, from day one, that they were managing a disease and not just patching an injury.