Your dog's patella, or kneecap, can become displaced in a fairly common condition known as medial patella luxation. The patella shifts to the inside of his knee joint and fails to glide in its groove of the femur (the leg bone above the knee). Other patella injuries include cranial cruciate ligament rupture, patella fractures, patella tendon rupture and collateral ligament injury.
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Medial Patella Luxation
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Medial Patella Luxation (MPL) may be due to a congenital defect, such as hip displasia, a developmental problem or trauma. It is most common among small dogs such as Maltese, Bichon Frise, Yorkshire Terriers and Poodles, but may be present in larger dogs. It may be partially or fully displaced and it can be a sporadic or permanent condition, producing lameness in your dog. It is diagnosed by physical examination and x-rays.
Lateral Patella Luxation
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With lateral patella luxation, the symptoms are the same as medical patella luxation. However, the patella becomes displaced to the outside of the knee, instead of the inside. This particular condition is more common in larger dogs. Diagnosis is made by physical examination and x-rays.
Cranial Cruciate Ligament Rupture
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Cranial cruciate ligament rupture may occur suddenly from a traumatic injury. The cruciate ligament holds the dog's femur (upper leg bone), tibia (lower leg bone) and knee joint together. It may also appear as a chronic condition with less significant lameness. Sometimes there may be a combined problem of torn cranial cruciate ligament along with luxating patella. A torn cruciate ligament may require surgery to correct.
Patella Fracture
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Patella fracture is not a common injury. It typically occurs following a direct blow to the knee such as being hit by a car. It causes acute lameness. X-rays are used to confirm the injury and surgery is required to remove fragments and repair the knee. Your dog may later develop arthritis in the knee as a result of the injury.
Diagnosis/Treatment
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Your veterinarian can diagnose your dog's condition by watching him walk, physical examination and x-rays. You need to inform him how long the problem has persisted, whether the lameness is the same or changes and when or if one knee is worse. Some patella injuries may be treated with restricted exercise and non-steroidal anti-inflammatory medications, but if it is severe it requires surgery to correct it.
Warning
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If you dog exhibits sudden or progressively worsening lameness, or shows signs of pain or discomfort, you should consult your veterinarian for diagnosis and treatment. Left untreated, some injuries may result in permanent lameness and the development of arthritis.
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