The cruciate ligament is a pair of ligaments which form an X shape within the knee of the hind leg. These ligaments attach the femur (thigh bone) with the tibia (shinbone), the long bones above and below the knee joint (which is known as the stifle joint in quadruped/four-footed animals).
The knee joint is held together and stabilised with four main ligaments, the medial and lateral collateral ligaments which run down the inside and outside of the knee and the anterior (cranial) and posterior (caudal) cruciate ligaments which sit within the knee joint. The cruciate ligament's role is to provide stability to the knee joint, preventing twisting of the bones or hyperextension of the knee joint.
A cruciate ligament rupture can occur due to a traumatic event which results in severe twisting or pivoting of the knee joint. Damage may also develop slowly due degeneration which can come with age. When the ligament ruptures, the entire joint becomes unstable and the leg bones can easily move out of place. It is also quite common for other parts of the joint such as the meniscus to be damaged at the same time as a cruciate rupture.
Ruptures may be partial or full (complete). A partial rupture means only one of the two cruciate ligaments has been torn, a full rupture occurs when both the cranial and posterior cruciate ligaments are torn.
There is a higher incidence of cruciate ligament ruptures in cats who are overweight.
What are the symptoms of a cruciate ligament rupture?
Cats with a ruptured cruciate ligament most commonly present with rear limb lameness, he may also hold the affected limb off the ground. Symptoms may be sudden onset if an injury or trauma are the cause or slowly progress over a period of time.
Other symptoms may include:
- Swelling of the affected area
- Pain if the limb is moved (please don't do this)
- Decrease in activity
How is a cruciate ligament rupture diagnosed in cats?
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. Questions he may ask include if the lameness occurred suddenly or has been slow and progressive. Has the cat been in a recent trauma such as a fall? As there are a number of causes of limping in cats, which may have similar symptoms, your veterinarian will need to narrow down the cause during the physical examination.
He will watch your cat walk as well as carefully perform an orthopaedic examination which includes a physical examination of the affected limb for swelling as well examining the physical structures around the joint. The joint will be carefully moved through several motions including a cranial drawer test and a tibial compression test which can be helpful in diagnosing a cruciate ligament rupture. This test may need to be carried out under anesthesia. He will evaluate the non-affected limb for comparison.
Radiographs may be taken of both the affected and non-affected leg to determine if a cranial rupture is evident as well as to look for signs of arthritis.
How is it treated?
Treatment may include exercise restriction for 6-8 weeks, as obesity can be a significant factor, weight loss will be necessary for overweight cats. Anti-inflammatory drugs and painkillers may be prescribed at this time.
Your veterinarian will need to monitor your cat for signs of improvement. If there is no change or the condition becomes worse surgical treatment will be necessary.
The drawback of this wait and see approach is there is a very good chance the affected stifle will develop arthritis in the future.
There are a number of methods to stabilise the joint surgically, this may be performed by your own veterinarian or he may refer you to a specialist. During surgery, the meniscus will also be evaluated for tears as this is a common concurrent injury in cats with a cruciate ligament rupture.
Your cat will be sent home with a care sheet with instructions on how to look after your cat during the recovery period. Always follow these instructions carefully.
Your cat may be reluctant to eat after surgery due to the anesthesia or painkillers. If this occurs, offer him some type of strong-smelling food such as tuna or cooked chicken breast as well as offering him food by hand. If he continues to refuse food, speak to your veterinarian.
Your cat's stifle joint will be immobilised for at least two weeks to allow the stifle to repair. He will be placed on strict cage rest during this time. Your veterinarian may recommend very short walks in a harness to encourage him to use the limb, but no running or jumping will be permitted for at least 12 weeks after surgery. Your cat should not be permitted outside (unless on a harness) during this time.
Painkillers will be prescribed for the first 10-14 days post surgery.
Be watchful for signs of infection including swelling, redness, oozing fluid or odour.
Follow-up visits will be required post surgery to remove change bandages, remove staples or stitches and evaluate the affected joint.