Dislocated patella: Difference between revisions
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==Overview== | ==Overview== | ||
'''Luxating patella''', or trick knee, is a condition in which the [[patella]], or kneecap, dislocates or moves out of its normal location. The luxation is usually medial, but can be lateral. | '''Luxating patella''', or trick knee, is a condition in which the [[patella]], or kneecap, dislocates or moves out of its normal location. The luxation is usually medial, but can be lateral. | ||
==Classification== | |||
There are four diagnostic grades of patellar luxation<ref>{{cite web | |||
| author = OFA | |||
| title = Patellar Luxation | |||
| publisher = [[Orthopedic Foundation for Animals]] | |||
| url = http://www.offa.org/patluxinfo.html | |||
| format = text/html | |||
| accessdate = 2007-09-04}}</ref>, 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 [[flexion]] of the stifle joint. The patella remains luxated until it is manually reduced or when the animal extends the joint and derotates the [[tibia]] 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 [[femur|femoral]] [[trochlea]]r groove is shallow or absent, and there is displacement of the [[quadriceps]] muscle group in the direction of luxation. | |||
==Pathophysiology== | ==Pathophysiology== | ||
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===X-Rays=== | ===X-Rays=== | ||
[[X-ray]]s are necessary in some cases. | [[X-ray]]s are necessary in some cases. | ||
==Treatment== | ==Treatment== | ||
Revision as of 14:00, 19 August 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Grace M. Gibson
Synonyms and keywords: dislocated kneecap; patellar subluxation; subluxation of the patella; subluxation of patella; luxating patella
Overview
Luxating patella, or trick knee, is a condition in which the patella, or kneecap, dislocates or moves out of its normal location. The luxation is usually medial, but can be lateral.
Classification
There are four diagnostic grades of patellar luxation[1], 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 flexion of the stifle joint. The patella remains luxated until it is manually reduced or when the animal extends the joint and derotates the tibia 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 femoral trochlear groove is shallow or absent, and there is displacement of the quadriceps muscle group in the direction of luxation.
Pathophysiology
It can be caused by some form of blunt trauma, or may be a congenital defect. In congenital cases, it is usually bilateral.
Natural History, Complications and Prognosis
Osteoarthritis can develop secondarily.
Diagnosis
Symptoms
Symptoms can range from none to severe pain.
Physical Examination
Diagnosis is made through palpation of the knee.
X-Rays
X-rays are necessary in some cases.
Treatment
Grades III and IV, as well as most grade II cases, require surgery to correct, if the animal has difficulty walking. The surgery involves a sulcoplasty, a deepening of the trochlear sulcus that the patella sits in.
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.
References
- ↑ OFA. "Patellar Luxation" (text/html). Orthopedic Foundation for Animals. Retrieved 2007-09-04.