Dislocated Kneecap (Luxating Patellas) in Cats

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Key takeaways

Patellar luxation is a condition that affects the kneecap, causing it to dislocate either towards the inside or outside of the leg.

  • In cats, this disorder is usually hereditary and develops gradually with age
  • It can also be caused by blunt physical trauma; symptoms in these cases are immediately evident
  • Common symptoms include lameness, skipping, and unwillingness or inability to jump
  • Sometimes symptoms can go unnoticed, especially with a lower grade luxation
  • In more severe cases, bone and limb deformities might become evident
  • Diagnosis involves a complete physical and orthopedic examination, and diagnostic imaging of the affected limb
  • Treatment ranges from rest and physical therapy to surgical correction
  • The prognosis varies according to the grade of the luxation and level of intervention and management needed
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A closer look: Dislocated Kneecap (Luxating Patellas) in Cats


Dislocated kneecaps are usually a progressive condition in cats. Some cases can be managed with environmental strategies and pain relief medications. More severe cases require surgical correction. As with other joint disorders (such as hip or elbow dysplasia), life-long abnormal wear and tear on the joint often leads to osteoarthritis later in life.

Patellar luxation can be divided into four different grades in which the symptoms become gradually more severe.

Grade I: mild and infrequent symptoms Grade II: the patella luxates and relocates frequently; self-resolving skipping lameness Grade III: mostly luxated patella; consistent lameness; bone deformities Grade IV: severe lameness and bone limb deformation

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Risk factors


Patellar luxation is a rare disorder in cats. With treatment, the condition can usually be corrected and most cats fully recover. The condition is genetic, with Devon Rex breed having the highest predisposition to chronic patellar luxation.

Possible causes


In most cases, patellar luxation is a genetically inherited disease. The joint and leg bones do not develop normally and the kneecap does not rest properly in position.

Dislocation can also be caused by blunt physical trauma, and in this case, clinical signs appear immediately instead of gradually developing.

Main symptoms


Testing and diagnosis


Diagnostics involve a complete physical examination, an orthopedic evaluation, and diagnostic imaging of the affected limb. Mild or low grade cases may be more difficult to diagnose, requiring more specialized imaging to confirm luxation and/or lab work to rule out other conditions.

Steps to Recovery


Treatment varies depending on severity of the disease. Some patients recover with crate rest or physical therapy, such as range of motion exercises. More severe cases are often corrected surgically. The goal of surgical correction is to permanently restore the patella to its ideal location. The type of surgical operation also varies depending on the severity of the luxation. In severe cases, limb amputation might be necessary.

After surgery, patients need supportive care (anti-inflammatories, warm and/or cold compressions of the limb), and homecare therapy which involves keeping a relaxed environment, and controlled exercise.

The prognosis varies according to the severity of the luxation. Most cats with grade I to III patellar luxations recover fully with surgery and have little risk of recurrence. In cats with grade IV luxation, the risk of recurrence is around 50%.

Due to the malpositioning of the kneecap, cats with patellar luxation are predisposed to joint arthritis. The prognosis of surgery before arthritis develops is excellent with most cats making a full recovery. If surgery is performed after arthritis develops, cats might require long-term supportive therapy such as pain control, joint supplements, or joint diets to slow the progression of the disease and reduce pain.

Prevention


The condition is not contagious. Due to its hereditary factors, avoiding using cats diagnosed with patellar luxation helps prevent passing the condition to future generations.

Is Dislocated Kneecap (Luxating Patellas) in Cats common?


Patellar luxation is rare in cats.

Typical Treatment


  • Surgical correction
  • Crate rest
  • Physical therapy
  • Supportive therapy
  • Pain relief medications
  • Anti inflammatories

References


Joseph Harari , MS, DVM, DACVS - Writing for Merck Veterinary Manual
Caleb Hudson, DVM, MS, Diplomate ACVS - Writing for Today's Veterinary Practice
No Author - Writing for Cornell University College of Veterinary Medicine
Malcolm Weir, Tammy Hunter, Cheryl Yuill - Writing for VCA Animal Hospitals
No Author - Writing for American College of Veterinary Surgeons

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