Cranial cruciate ligament rupture: what about the other stifle?
6-year-old neutered male Labrador Retriever, 36 kg (body condition 7/9), lame on the left hind limb after running in the park. Cranial drawer and tibial compression test are positive in the left stifle; the right is stable but has mild effusion. The owners ask whether the other stifle is at risk.
What do you tell them?
chevron_right Show answer and explanation
A. That the rupture was traumatic from running, so the risk to the other stifle is the same as in any healthy dog
In dogs, rupture is usually the end stage of progressive ligament degeneration; the acute episode is just the trigger. Purely traumatic rupture is uncommon.
B. That the right stifle should be operated on prophylactically now, even though it is stable
Prophylactic surgery on a stable, clinically normal stifle is not established practice. The right approach is to monitor it and act if lameness or instability develops.
C. That the disease is usually degenerative and bilateral: a substantial proportion of dogs (roughly a third to a half) rupture the contralateral ligament within 1–2 years, more so if effusion is already present
Correct. Cruciate rupture in dogs is mostly degenerative. Effusion or osteophytes in the apparently normal stifle indicate disease already under way and increase the risk of rupture. Excess weight is a modifiable risk factor.
D. That contralateral rupture only happens from overload during convalescence, so strict rest is enough
Overload may precipitate it, but the underlying cause is ligament degeneration. Rest does not stop the disease from progressing in the other stifle.
lightbulb Key takeaway
Warn owners about the contralateral risk at the first consultation so they do not interpret it as surgical failure. Bringing the dog to its ideal weight is the most useful measure to protect both stifles.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.