In this post I will do my best to explain and simplify things that you need to know regarding a cruciate ligament injury and their consequences.
A cranial cruciate injury is the most common source of rear limb lameness in dogs. The cranial cruciate ligament or CCL is also known as the Anterior cruciate ligament or ACL, but this is the term used in humans. Many times veterinarians use this term since people are more familiar with it, and makes it easier to understand, however, the proper name of this ligament in dogs is the Cranial Cruciate ligament or CCL.
This ligament is inside the knee joint (also called stifle joint). The knee is formed by 3 bones, the femur (or thighbone), the tibia (or shin bone) and the patella (or knee cap). The sections of these bones that form the knee are surrounded by cartilage, and this is enclosed by a thick layer of tissue called the joint capsule. Inside the capsule is fluid called joint fluid (synovial fluid).
If you look at the knee joint from the back you’ll see two ligaments that form a cross, these are the cruciate ligaments. They are the caudal cruciate ligament and the cranial cruciate ligament. Injuries to the cranial cruciate ligament are very common, injuries to the caudal cruciate ligament are rare.
The function of the cranial cruciate ligament (CCL or ACL) is to keep the tibia from sliding forward under the femur (tibial thrust) as well as to prevent the internal rotation of the tibia. In other words, the function of the cruciate ligament is to maintain appropriate contact between the femur and the tibia and good alignment of these two bones during walking, running or standing.
Inside the knee joint, dogs as we do have something called meniscus. These are shock absorbers, they are at the top of the tibia, and the femur (thigh bone) sits on top of them.
When a dog has torn a CCL the femur will slide backwards on the tibia, and the tibia will move forward (tibial thrust, also called cranial tibial subluxation). The femur will move on top of the tibia and meniscus making pressure against areas of the joint that are not used to receiving this much weight bearing, causing damage of the cartilage and meniscus (commonly causing meniscal tears). All of these changes will cause joint swelling (inflammation) and pain.
Rupture of the cranial or anterior cruciate ligament (CCL or ACL) can be acute (sudden) or chronic (over a period of time) in nature. Acute injuries can be traumatic sports injuries in active dogs, and most commonly occurs due to over/hyperextension and internal rotation/twisting inwards of the knee (often occurring when a dog steps in a hole or any type of force stressing the ligament that exceeds its breaking strength while the pet is active). Proposed underlying causes for chronic disease of the CCL include age-related deterioration of the ligament, obesity, conformation abnormalities of the rear limb, and immune-mediated disease.
Partial or incomplete tears of the Cranial cruciate ligament (CCL, ACL) most of the time does not cause as much joint instability but can be as painful and requires same treatment as a complete tear/rupture.
I will talk about diagnosis for this injury on a separate post as well as the surgical treatments available such as Tibial Tuberosity Advancement or TTA, Tibial Plateu Leveling Osteotomy or TPLO, Extracapsular technique, Tight Rope, etc.
And please don’t hesitate to make any comments, or share this post, any input is always appreciated.
Marcos Haase, DVM
Related posts: