Skipping lameness: cruciate rupture

What is a cruciate ligament rupture

The cranial cruciate ligament (CrCL) is a band of tough fibrous tissue that attaches the femur to the tibia, preventing this one from shifting forward. It also helps to prevent the stifle joint from over-extending or rotating.

In the vast majority of dogs, the cranial cruciate ligament (CrCL) ruptures as a result of long-term degeneration, whereby the fibres within the ligament weaken over time. We do not know the precise cause of this, but genetic factors are probably most important, with certain breeds being predisposed. Other factors such as obesity, individual conformation, hormonal imbalance and certain inflammatory conditions of the joint may also play a role.

What is the typical clinical presentation and why it’s important not to mistake it with a neurological problem

A non-weight bearing lameness is the commonest sign of CrCL injury. This may appear suddenly during or after exercise in some dogs, or it may be intermittent in others. Some dogs are simultaneously affected in both knees, and these dogs often find it difficult extend the knee, almost walking like a frog. A bilateral CrCL rupture could be mistaken with a neurological disease affecting the L4-L6 spinal cord or bilateral femoral nerves. In severe cases, dogs won’t be able get up at all and some people might mistake this for a paralysis.

How will we know if this is a CrCL or a neurological problem? By performing a proper orthopedic and neurological examination

Clinical examination in a CrCL rupture

There will be laxity of the stifle and pain. In more chronic changes the stifle will feel abnormal and swollen. In dogs with partial tears or early degeneration of the ligament changes might be very subtle and further imaging might be necessary.

What is extremely important to remember, that a dog with a CrCL rupture will have a normal neurological examination. You won’t have proprioceptive deficits or ataxia. However, remember to support properly the dog’s weight, otherwise you neuro exam might seem abnormal, just because the dog can’t hold the weight on that painful stifle.

Why do I know on this video this is a stifle problem and not a neurological problem

What can we see on this video, at first, there is some weakness on the left hind limb, there’s like a strange movement and almost looks like an unstable. But there is NO ataxia, so no incoordination and there is no dragging or scuffing. The most important trick here is that left hind limb is hopping! Non weight bearing lameness are almost never from a neurological origin. On this dog, the fact that we have that hopping, that skipping when walking and a normal neuro exam is telling us this is NOT neurological. Then we perform an orthopedic examination and we confirm it’s a cranial cruciate ligament rupture.