Luxating patella
Encyclopedia
Luxating patella is a condition in which the patella, or kneecap, dislocates or moves out of its normal location.
Patellar luxation is a common condition in dog
s, particularly small and miniature breeds. The condition usually becomes evident between the ages of 4 to 6 months. It can occur in cat
s as well, especially the Domestic Shorthair
.
It also occurs in humans, where it can be associated with damage to the anterior cruciate ligament
.
, Maltese, Jack Russell Terrier
s, Yorkshire Terrier
s, Pomeranian
s, Pekingese
, patterdale terrier, Chihuahua
s, Cavalier King Charles Spaniel
s, Papillon
s, Boston Terrier
s and Teddy Roosevelt Terrier
s. Large breed dogs are also affected and the Labrador retriever seems particularly predisposed. Patellar luxation is less common in cat
s than in dog
s. Predisposed breeds include the Devon Rex
and the Abyssinian
. Although the specific cause of patellar luxation is unknown in these cases, it is generally agreed that a defect in hind limb conformation is the underlying cause.
Luxating Patella cannot be present without the knee being loose, but a loose knee is not necessarily slipping out of the joint. Even with Luxating Patella, there may be no symptoms or only mild ones, such as intermittent limping in the rear leg. X-Rays can determine how serious the condition is. More extreme cases can result in severe lameness. Osteoarthritis
typically develops secondarily.
There are four diagnostic grades of patellar luxation, each more severe than the previous:
to correct, if the animal has difficulty walking. The surgery required is governed by the type of abnormality present, but often involves a sulcoplasty
, a deepening of the trochlea
r sulcus that the patella sits in, a re-alignment of the attachment of the patella tendon on the tibia, and tightening/releasing of the capsule either side of the patella, according to which side the patella is slipping. Some Grade IV conditions may require more involved surgery to realign the femur and/or tibia.
Additional help can be given with the use of pet ramps, stairs, or steps. These can help the animal travel from one place to another, especially up and down, without adding any pain or damage to the patella.
Patellar luxation is a common condition in dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, particularly small and miniature breeds. The condition usually becomes evident between the ages of 4 to 6 months. It can occur in cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s as well, especially the Domestic Shorthair
Domestic shorthaired cat
A domestic shorthaired cat is a cat fancy term used to describe a shorthaired cat that does not have a pedigree or belong to a recognized cat breed...
.
It also occurs in humans, where it can be associated with damage to the anterior cruciate ligament
Anterior cruciate ligament
The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...
.
Presentation
Most cases of patellar luxation are medial and this is frequently a congenital problem in toy and miniature breed dogs. Breeds showing a predisposition for medial patellar luxation include miniature and toy PoodlesPoodle
The Poodle is a breed of dog. The poodle breed is found officially in toy, miniature, and standard sizes, with many coat colors. Originally bred as a type of water dog, the poodle is highly intelligent and skillful in many dog sports, including agility, obedience, tracking, and even herding...
, Maltese, Jack Russell Terrier
Jack Russell Terrier
The Jack Russell terrier is a small terrier that has its origins in fox hunting. It is principally white-bodied smooth, rough or broken-coated which is commonly confused with the Parson Russell terrier and the Russell terrier with the term "Jack Russell" commonly misapplied to other small white...
s, Yorkshire Terrier
Yorkshire Terrier
The Yorkshire Terrier is a small dog breed of terrier type, developed in the 19th century in the county of Yorkshire, England to catch rats in clothing mills. The defining features of the breed are its size, to , and its silky blue and tan coat...
s, Pomeranian
Pomeranian (dog)
The Pomeranian is a breed of dog of the Spitz type, named for the Pomerania region in Central Europe . Classed as a toy dog breed because of its small size, the Pomeranian is descended from the larger Spitz type dogs, specifically the German Spitz...
s, Pekingese
Pekingese
The Pekingese, or "Peke" is an ancient breed of toy dog, originating in China. The breed was favored by the Chinese Imperial court, and its name refers to the city of Beijing where the Forbidden City resides...
, patterdale terrier, Chihuahua
Chihuahua (dog)
The ' is the smallest breed of dog and is so named for the state of Chihuahua in Mexico. Chihuahuas come in a wide variety of sizes, head shapes, colors and coat lengths.-History:...
s, Cavalier King Charles Spaniel
Cavalier King Charles Spaniel
The Cavalier King Charles Spaniel is a small breed of Spaniel-type dog, and is classed as a toy dog by most kennel clubs. It is one of the most popular breeds in the United Kingdom. Since 2000, it has been growing in popularity in the United States. It is a smaller breed of spaniel, and Cavalier...
s, Papillon
Papillon (dog)
The papillon , also called the Continental Toy Spaniel, is a breed of dog of the Spaniel type. One of the oldest of the toy Spaniels, it derives its name from its characteristic butterfly-like look of the long and fringed hair on the ears. A papillon with dropped ears is called a phalène...
s, Boston Terrier
Boston Terrier
The Boston Terrier is a breed of dog originating in the United States of America. This "American Gentleman" was accepted in 1893 by the American Kennel Club as a non-sporting breed. Color and markings are important when distinguishing this breed to the AKC standard. They should be either black,...
s and Teddy Roosevelt Terrier
Teddy Roosevelt Terrier
-Description:The Teddy Roosevelt Terrier is an American hunting terrier that is a small to medium sized terrier. Lower-set with shorter leg, more muscular, and heavier bone density than its cousin the American Rat Terrier...
s. Large breed dogs are also affected and the Labrador retriever seems particularly predisposed. Patellar luxation is less common in cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s than in dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s. Predisposed breeds include the Devon Rex
Devon Rex
The Devon Rex is a breed of intelligent, short-haired cat that emerged in England during the 1960s. They are known for their slender bodies, wavy coat, and large ears, similar to the Cornish Rex.-Discovery and relations:...
and the Abyssinian
Abyssinian (cat)
The Abyssinian is a breed of domesticated cat with a distinctive ticked coat. There are many stories about its origins, often revolving around Ethiopia, but the actual origins are uncertain...
. Although the specific cause of patellar luxation is unknown in these cases, it is generally agreed that a defect in hind limb conformation is the underlying cause.
Causes
Rarely, it can be caused by some form of blunt trauma, but most frequently, it is a developmental congenital defect. In congenital cases, it is frequently bilateral. The condition can also be inherited through genetics. This can also be caused by obesity.Diagnosis
Diagnosis is made through palpation of the knee, to see if it slips inside the joint more than would normally be expected. Often a dog-owner may be told his pet has "loose knee," but this is not a medical term, and it is not correct to use it interchangeably with Luxating Patella.Luxating Patella cannot be present without the knee being loose, but a loose knee is not necessarily slipping out of the joint. Even with Luxating Patella, there may be no symptoms or only mild ones, such as intermittent limping in the rear leg. X-Rays can determine how serious the condition is. More extreme cases can result in severe lameness. Osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
typically develops secondarily.
There are four diagnostic grades of patellar luxation, each more severe than the previous:
- Grade I - the patella can be manually luxated but is reduced (returns to the normal position) when released;
- Grade II - the patella can be manually luxated or it can spontaneously luxate with flexionFlexionIn anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
of the stifle joint. The patella remains luxated until it is manually reduced or when the animal extends the joint and derotates the tibiaTibiaThe tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
in the opposite direction of luxation; - Grade III - the patella remains luxated most of the time but can be manually reduced with the stifle joint in extension. Flexion and extension of the stifle results in reluxation of the patella;
- Grade IV - the patella is permanently luxated and cannot be manually repositioned. There may be up to 90¼ of rotation of the proximal tibial plateau. The femoralFemurThe femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
trochleaTrochleaTrochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
r groove is shallow or absent, and there is displacement of the quadriceps muscle group in the direction of luxation.
Treatment
Grades II, III and IV require surgerySurgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
to correct, if the animal has difficulty walking. The surgery required is governed by the type of abnormality present, but often involves a sulcoplasty
Sulcoplasty
Sulcoplasty is an orthopedic surgical procedure performed on a groove or indentation present on particular bones. In veterinary surgery it is often employed to remedy a displaced kneecap by deepening the trochlear sulcus, the groove on which the patella normally sits....
, a deepening of the trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
r sulcus that the patella sits in, a re-alignment of the attachment of the patella tendon on the tibia, and tightening/releasing of the capsule either side of the patella, according to which side the patella is slipping. Some Grade IV conditions may require more involved surgery to realign the femur and/or tibia.
Additional help can be given with the use of pet ramps, stairs, or steps. These can help the animal travel from one place to another, especially up and down, without adding any pain or damage to the patella.
External links
- The KNEEguru - educational site packed with knee content with sections on patellar luxation
- Luxating Patella Informational Guide to Luxating Patella