If one knee is already a problem, is the other one still insured?

Usually not. If one side was already known before your policy started, or during the waiting period, most insurers treat the matching condition on the other side as pre-existing too. That is the bilateral rule, and all four insurers in this register apply it. It is why a dog with one dysplastic hip is often uninsurable for the second.

What counts as a bilateral condition?

Anything the body has two of. Hips, elbows, knees, eyes. Trupanion's policy names them in its definitions: elbow dysplasia including fragmented coronoid process, ununited anconeal process and osteochondritis dissecans, cruciate issues, luxating patella, hip dysplasia, cherry eye, entropion and ectropion, panosteitis, and cataracts. That list is a useful thing to keep, because it is roughly the list of conditions that make purebred dogs expensive.

The definitions are not identical, and the differences matter. Lemonade calls a bilateral condition "a chronic condition that affects both sides of your pet's body, even if clinical signs or symptoms do not present at the same time". The clause about time is the point: a gap of two years between the left hip and the right one does not make them two conditions.

Which insurer's rule reaches the most conditions?

Trupanion. Counted across the thirteen conditions in this register, its rule reaches eight of them, Lemonade's reaches five, and Spot and Figo reach two each. That is the opposite of what the wording alone suggests, and it is worth knowing why: a policy that lists its bilateral conditions by name, as Trupanion does, reaches every condition on that list. A policy that names only one group reaches only that group, however strongly it is phrased.

Spot and Figo are the clearest illustration, because they are the same clause. Both are underwritten by Independence American Insurance Company and both define Ligament and Knee Conditions in identical words, down to the phrase regardless of cause. The difference is the clock in front of it: Spot puts knee conditions on the same fourteen days as everything else, while Figo puts orthopedic conditions on six months. Same carrier, same sentence about the second side, and a materially different first year.

And which one is phrased most strongly?

Spot and Figo, within the group they cover. Both define Ligament and Knee Conditions as covering a ligament, patella, meniscus or soft tissue disorder of the knee, and then say these "are considered bilateral conditions and related, regardless of cause; meaning an occurrence on one side of the body affects both sides of the body". Regardless of cause is a wide phrase. A torn cruciate from a fall on one leg is, under that wording, related to a future problem in the other knee. But an elbow is not in that list, and neither is a hip, so the same clause stops where the sentence stops.

These two questions have different answers and both are on the page because a reader deciding between policies needs both. Reach tells you how many of your breed's problems the rule can touch. Phrasing tells you how hard it bites where it does apply. Neither is the whole answer on its own.

That is also not a reason to avoid Spot. Its waiting period for exactly those knee conditions is 14 days where two others take 30 and Figo takes six months, so the same policy is quicker to start and stricter about the second side. Which of those matters more depends on whether your dog already has a knee history, and that is a question only you can answer.

When does this rule not hurt you?

When both sides are healthy when you enrol. The bilateral rule is a pre-existing rule; it looks backwards, not forwards. If neither knee has ever been treated and neither hip has ever been imaged with a finding, then a first cruciate rupture after the waiting period is covered, and so is the second one that follows a year later, because the first was covered rather than pre-existing.

One policy in this register narrows that comfort. Figo states that genetic conditions, ligament and knee conditions, orthopedic conditions and chronic conditions are never considered cured, where the same document lets an ordinary condition return to cover after 365 symptom-free days. So for exactly the conditions this page is about, a Figo exclusion does not expire.

This is the whole reason the timing of enrolment matters more in pet insurance than in almost any other product. Every week you wait is a week in which something can be written into a clinical record, and a note in a clinical record is what turns a covered condition into an excluded one.

What should you check before you sign?

Three things, all in the policy document rather than the marketing pages. Whether the insurer defines a bilateral condition at all, because one that does not may still apply a general pre-existing rule to the same effect. Whether the definition names conditions or describes a class, because that is what decides how far it reaches. And whether the waiting period for that class is longer than the general illness one, because a six month orthopedic wait plus a bilateral rule is a very different product from a 14 day wait with the same rule.

We have not bought any of these policies and have not filed a claim under one. Everything on this page is read from the documents linked in each row. The reach figures above are counted from the rows in this register, so they change as it grows.