A trick knee or dislocating kneecap is really a medial luxating patella. This is a common problem in toy and small breed dogs. However, it may occur in large breed dogs as well . The characteristic lameness is a little skip in your pet’s step but can be as severe as running on three legs. However, unlike a torn cruciate the dog will suddenly recover as if nothing had happened.
Knee Joint Anatomy Consists of:
- The femur above
- The tibia below
- The kneecap (or patella) in front
- Two small bones called the fabellae behind.
- A figure eight cartilage cushion called the meniscus between the bones
- Several ligaments that keep the joint in alignment
When the patella luxates, the kneecap (patella) has slipped out of the smooth grove that it normally rests in and glides up and down in. When the kneecap dislocated, the knee cannot fully extend correctly and stays bent.
Hopefully they can return the kneecap to normal position, but if the kneecap luxates routinely, over time the friction wears the grove flattening it. In these cases, surgery is required to repair the joint.
Which dogs need surgery?
Patella luxation is graded on a system of 1 to 4 based on severity and how much time the kneecap is out of position:
Grade 1: With manual manipulation the kneecap can be moved out of the grove, but when the manipulation is removed it falls back into place.
Grade 2: The kneecap can be moved out the grove with manual manipulation, but this time the kneecap does not return to normal position when the manipulator lets go. Surgery is beneficial for these dogs as arthritis and further damage to the knee can develop over time.
Grade 3: The patella is consistently out of place , but can be replaced with manipulation to its normal position. However, without manipulation the kneecap will not stay in place. Surgery is recommended to return to normal function.
Grade 4: The patella may always be out of place, and the bone is sufficiently worn down so that it can not be replaced in the grove even with manipulation. In these cases dogs have difficulty extending the knee and walks with bent knees almost all the time. surgery is necessary to return normal function.