Zoey’s ACL Injury Part 2

While clinical history and physical exam findings are helpful in allowing us to suspect a ruptured ACL, further diagnostics are needed to confirm the ligament is torn.  Typically, this involves sedation and xrays of the knee.  These animals usually need sedation because the knee is so painful it is difficult for us to manipulate, as they tense their muscles to resist movement of the joint.  A combination of a sedative and a pain medication is used to allow the animal (and subsequently muscles!) to relax to allow a full manipulation and examination…as well as making them perfectly still for xrays!

A standard abnormal finding of a ruptured cruciate ligament is the demonstration of an abnormal knee motion called a drawer sign. It is not possible for a normal knee to show this sign.  When we attempt to find a cranial drawer sign, we stabilize the position of the femur with one hand and manipulate the tibia with the other hand. If the tibia moves forward, the cruciate ligament is ruptured.

If the rupture is older, there is swelling on side of the knee joint that faces the other leg. This is called a “medial buttress” and is indicative of arthritic changes in the joint.

After manipulation to find cranial drawer, xrays are taken of the knee as well as the hips.  Hip xrays are helpful to determine if there is any preexisting arthritis or congenital abnormalities that could influence surgery.  Xrays of the knee allow a surgeon to calculate the angle of the knee necessary for surgical repair.

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