Kneecap Dislocation in Cats

In the veterinary world, kneecap dislocation in cats is termed “feline luxating patella”. The patella is, of course, the medical term for kneecap and luxation means to dislocate. A luxating patella will cause the feline to display an unusual gait, as the knee joint cannot function as it would normally. Kneecap dislocation can be caused by a variety of reason that may or may not require immediate medical addition, which is why it is of the utmost importance for a veterinary professional to be consulted when signs are first noted. 

When your cat engages in physical activity and suddenly begins to limp, your feline could have suffered a kneecap dislocation. The knee, or stifle, of a cat has the identical structure of a human knee. The leg’s long bone (the femur) and two short bones (the tibia and fibula) are connected together with tendons to form the knee, as well as muscle to provide hinge movement to the leg. The kneecap, or patella, protects the knee and is housed in a groove known as the trochlear groove. When the kneecap dislocates, it means that the kneecap structure has “popped out” of the trochlear groove. 

Kneecap dislocation in cats will cause what veterinarians call mechanical lameness. The kneecap is causing an abnormal pull on the leg bones of the cat, mechanically inhibiting her from moving the leg in proper form. Mechanical lameness differentiates from standard lameness, as it does not cause the feline pain. Kneecap dislocation in cats will cause the feline to hold the affected hind leg abnormally, causing her to walk with a limp. Over time, affected cats have learned how to pop the kneecap back into place with a couple kicks of the leg, but this action will eventually damage the stifle structures and make the issue worse over time.

Types 

• Medial Luxation (MPL): A medial luxated patella is the term used when the feline holds the leg outward from the body. 
• Lateral Luxation (LPL): A lateral luxated patella is the term used when the feline holds the leg inward, toward the body. 

Kneecap dislocation in cats can be caused by one of the following reasons:

• A hereditary defect causing a congenital malformation 
• Congenital malformation
• Injury or trauma 

A kneecap dislocation following a traumatic event, such as a hit-by-car incident, is usually caused by an injury to the hip, leg, or knee itself. Injury or trauma related kneecap dislocation is normally just present in one of the hind legs and can often be reversed with surgical procedures. Hereditary or congenital kneecap dislocation, however, is an inherited mutation of the skeletal system, often affecting both hind limbs. The condition is present in the feline’s DNA, passed down from one or both parents to the offspring. Inherited kneecap dislocation can come and go, or become a permanent luxation over time. 

Diagnosis of kneecap dislocation in cats is fairly simple, as patellar luxation is initially diagnosed through direct palpation of the luxated patella. In other words, the veterinarian will use his/her hands to feel the kneecap pop in and out of place. Discussing your feline’s at-home symptoms and behavior, paired with a review of her medical history, will help confirm the diagnosis. To complete the diagnosis, the veterinarian will ask to have x-rays taken of the affected legs, which will completely confirm the diagnosis as well as indicate the extent of the problem. 

Kneecap dislocation in cats is graded by level of severity on a scale of one to four to determine whether or not the cat is a good surgical candidate. 

A level 1 grade patella luxation is the least severe. A cat with a level 1 grade kneecap dislocation can return the patella back to normal position easily and shortly after the issue occurs. Level 1 patella luxation does not normally require any treatment as felines can usually go their whole lives without the abnormality becoming an issue. However, as the cat ages and arthritis sets in, or if the cat becomes obese, the joint becomes too stressed to be left untreated. 

A level 4 grade patella luxation is the most severe. A cat with a level 4 grade kneecap dislocation cannot return the patella back to its normal location and it remains out of place indefinitely. A level 4 patella luxation can result in chronic lameness if left untreated and possibly the inability to use said leg at all in the future. 

Levels 1-2 patella luxation may not be surgically treated until a later date, if at all. However, level 3-4 patella luxation cases are strongly encouraged to seek surgical treatment to fix the problem before permanent damage is done. 

Surgery is usually very successful for kneecap dislocation in cats, with about a 50 percent chance the condition will reoccur. After surgery, you will need to monitor your cat’s bandages and keep her in a quiet place to recover. Pain medication, anti-inflammatory drugs and/or an antibiotic may be sent home with the patient to be administered as instructed. Check-ups are a common occurrence during the recovery time and x-rays may be taken to ensure the stifle joint is in working order. It is not uncommon for your veterinarian to recommend physical therapy for your cat to help her to return to daily activity. The veterinarian may advise a few therapeutic movements to try at home or recommend an animal physical therapy professional.