Injury Or Rupture Of A Cruciate Ligament

Rupture of the cranial cruciate ligament is a common canine injury and it is an injury that occurs far less commonly in cats.  Cruciate injuries occur in humans and particularly to football players.  It occurs when there is extreme internal rotation of the lower leg causing tearing or complete rupture of the ligament.  Click HERE to see a recent case.

Common Causes

·        Dog placing its foot in a hole or getting it caught in a fence

·        Jumping especially if the landing is awkward

·        Sudden turning on a weight bearing leg often during play or while being chased

 

Why does it occur?

  • Cruciate rupture may be acute but often there is a degree of chronicity i.e. ligament already weakened
  • Age - cruciate ligaments weaken with age
  • Breed – seen more commonly in large breed dogs
  • Genetics – poor conformation
  • Disease - immune mediated disease can affect joints

Cruciate rupture is most common in large breed dogs that are middle aged or older and overweight.  Cruciate injury is also common in young, active large breed dogs.

In a study of 114 cases, 37% of the dogs went on to rupture a cruciate ligament in the other leg after an average of 17 months.

Type of Cruciate Injury

·        Acute Rupture

    • Sudden onset of non-weight bearing or partial weight bearing lameness.   Lameness may improve within 3-6 weeks but prognosis varies largely dependent on the size of the dog
    • Dogs weighing less than 10kg are likely to improve but will probably have reduced leg function and increased chance of developing arthritis and chronic lameness in the future
    • Dogs weighing more than 10kg may improve but very likely to have reduced joint function and a much higher probability of developing serious arthritis and chronic lameness

·        Partial Tear

    • Mild, non-weight bearing lameness that may resolve with rest.  Continued degeneration results in reduced joint stability, persistent lameness and chronic arthritis
    • Common, but tear usually deteriorates over a period of six months

Treatment Options

  • Dogs
    • Under 10kg
      • Potential for return of some function
      • Surgical repair enhances potential for return of good limb function and far more rapidly
    • Over 10kg
      • With conservative therapy some patients will regain some function as arthritis stabilizes the joint
      • Surgical repair recommended canine patients of all sizes to ensure optimum function
  • Cats
    • Conservative management – normal return of function within 5 weeks

Conservative Management vs. Surgical Fixation

  • Conservative Management
    • 6 weeks strict rest and anti-inflammatories BUT there is potential for persistent instability and chronic lameness as a result of continued arthritis
    • The healing potential of ligaments is very poor so while lameness may diminish over time it is not because the ligament has healed and that is why with conservative management the joint will have reduced function
    • There is often a subtle shift in weight on to the good leg and thus increasing its work load and the risk of cruciate rupture on the other leg
  • Surgical fixation
    • A new ligament is placed.  For a detailed description follow this link (warning - surgical images)
    • Prognosis
      • Generally good – 85 –90% of dogs improve after surgery
      • About 5% may require a second operation on the same leg
    • Surgical aftercare
      • Strict rest is vital for the first month followed by a slow introduction of exercise.  If movement of the dog is not restricted there is an increased likelihood that the surgical fixation will fail
      • Antibiotics and anti-inflammatories
      • Cartrophen injections - one injection every week for four weeks to reduce arthritis
      • Wound dressing – after surgery the leg is bandaged to reduce movement of leg – vital not to let your dog chew the bandage
      • Bandage off and sutures out after 14 days

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