Cruciate ligament rupture in dogs

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Interpreting the symptoms correctly

If a dog suddenly only uses one of its two hind legs or is excessively unwilling to put any weight on the hind legs, a cruciate ligament rupture is probably the cause. You should visit the vet as soon as possible as the failure can result in severe osteoarthritis or even permanent lameness.

What function does the cruciate ligament perform?

The cruciate ligament is a tendon in the knee joint. There is an outer, inner, front and rear cruciate ligament. It is used to stretch the leg. The ligaments cross in the centre of the knee joint, hence the name. Together with the other structures of the knee ligaments, the cruciate ligaments are used to stabilise the joint during every movement.

What is a cruciate ligament rupture?

A cruciate ligament rupture or tear is one of the most frequently-occurring orthopaedic injuries in dogs. In most cases, the rupture occurs during normal activities. Chasing after a cat or getting a paw caught while at full tilt is all it takes. However, depending on the age of the dog and whether the ligaments are already weakened, something as simple as stepping into a hole or uneven terrain can cause the cruciate ligament to tear. The rupture of the anterior cruciate ligament is the most common ligament rupture in dogs. If the cruciate ligament tears in humans, it usually does so there and then. In dogs, the ligament almost never ruptures at once, but tears fibre by fibre/bit by bit. For this reason, a rupture in dogs is mostly the result of an existing injury to the cruciate ligament.

When does the cruciate ligament tear or rupture?

The cruciate ligament can tear or rupture as a result of an accident (trauma) or due to wear (degenerative). This can be exacerbated by the normal ageing process or by constant overstressing (e.g. due to excess weight, high levels of physical exertion or the abnormal development of the tibia).

What symptoms occur when a cruciate ligament ruptures?

The extent of the symptoms can vary from dog to dog. Many owners report that a rupture is accompanies by whimpering of the pet. However, cruciate ligament ruptures often also remain undetected to begin with. Although the dog is lame in the hind quarters for a short period (2-3 days), it then often displays no symptoms at all for several weeks thereafter. Observe your dog closely. Is it running differently? Is it sitting differently? How does it place its paws when turning around? Dogs with a cruciate ligament rupture are very reluctant to move and continuously lose muscle mass.

The torn cruciate ligament will not heal by itself.

With small and lightweight dogs, conservative treatment may be possible under certain circumstances. However, if the injury is not operated on, there is a risk of dogs suffering meniscus damage. In the worst-case scenario, the cruciate ligament on the healthy side may also rupture due to the constant overstressing. With surgical treatment, consequential damage occurs much less frequently if the knee joint is stabilised in good time.


The vet will check the mobility of the knee joint, usually using what is referred to as the drawer test. This is easier to perform on small dogs than on large dogs due to their muscular strength. If the front cruciate ligament has ruptured completely, the lower leg can be pulled forwards like a drawer relative to the upper leg because the cruciate ligament no longer holds it in place. Furthermore, the effusion caused by the tear in the knee can be clearly felt.

Therapy/treatment options for a cruciate ligament rupture

There are numerous therapeutic options/methods. However, the surgical method used should be appropriate to the dog in question. For instance, is the dog still young, heavy or extremely agile?

The most common surgical techniques are:

  • Ligament replacement
  • Tightening the capsular fibre
  • TPLO (Tibial Plateau Leveling Osteotomy)
  • TTO (Triple Tibial Osteotomy)
  • TTA (Tibial Tuberosity Advancement)


Irrespective of the method used, the dogs should begin physiotherapy as soon as the stitches are removed. Strict weight control and moderate activity are other important measures after the operation. On completion of successful treatment, the dog will no longer suffer any impairment.