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Answers from vets about your cat:

Could My Cat Have a Deranged Knee?

Posted October 01, 2014 in

Dr. Phil Zeltzman is a traveling, board-certified surgeon in Allentown, PA. His website is He is the co-author of “Walk a Hound, Lose a Pound” (

Kelly Serfas, a Certified Veterinary Technician in Bethlehem, PA, contributed to this article.

Cat laying on a chair

Max, a gorgeous 6-year-old kitty, was sleeping on a reclining chair when he was abruptly woken up by pots and pans falling on the kitchen floor. Terrified, he tried to jump from the recliner. Somehow, his right, back leg got caught and prevented him from running away from the perceived danger.

A few hours later, his guardian found him hiding under the bed, shivering and clearly painful in the back leg. Max’s guardian immediately took him to the family veterinarian, who observed him limping around the exam room. The veterinarian initially suspected a torn ACL. Upon further exam, the veterinarian declared: "I think your Max has a deranged knee!"

What’s a deranged knee?
Max’s guardian asked what this bizarre condition was. The veterinarian explained that there are four ligaments in the knee: two inside the knee (anterior and posterior cruciate ligaments) and two outside the knee (collateral ligaments). When more than one ligament is torn, the knee is so severely affected, that the condition is called a deranged knee.

Most of the time, both cruciate ligaments and one collateral are torn. Occasionally, with very violent trauma, all four ligaments are torn.

How is a deranged knee treated?
A deranged knee is so wobbly that the only reasonable treatment is surgery. The goal is to make the knee more stable. Post-op care involves a combination of strict rest, pain management and physical therapy.

Max was referred to a board-certified surgeon (yours truly). When a cat’s leg gets caught somewhere, often in a piece of furniture, it classically leads to a deranged knee. Sure enough, Max had three torn ligaments (one collateral and both cruciate ligaments). They were repaired with heavy nylon sutures to mimic or imitate the original ligaments. Max went home the day after surgery.

Recovering from a deranged knee
After two weeks of confinement and physical therapy, Max had his stitches removed. At that point he was "toe-touching," which means that he was starting to put gentle pressure on the foot. After another six weeks of strict rest and physical therapy, he had another progress exam: he was using the leg very well.

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Dr. Phil Zeltzman is a board-certified veterinary surgeon and author. His traveling practice takes him all over Eastern Pennsylvania and Western New Jersey. You can visit his website at, and follow him at