Clinically normal cats have some degree of laxity in the stifle joint, with subluxation of the patella considered to be a common finding in healthy cats.1 In contrast, patellar luxation has been reported infrequently in cats.1–11 In cats with patellar luxation, the patella usually luxates medially, and the condition may be unilateral or bilateral.7 Patellar luxation can result from congenital malformations or trauma, and there are conflicting reports regarding the relative frequency of congenital versus traumatic patellar luxation in1–5,7,9,10 In general, however, congenital luxation is believed to be more common.1,7 It has also been suggested that there is a weak association between patellar luxation and hip dysplasia in cats.1
Clinical signs of patellar luxation may include intermittent locking of the stifle joint following extension7 or a shuffling or crouching gait.5 Although patellar luxation may result in lameness, affected cats are not always lame, and occult patellar luxation may be an incidental finding.3,5,7 Surgical repair has been reported to provide favorable results5,7; however, it has been stated that lame cats have a better clinical outcome following nonsurgical rather than surgical treat-ment.12 In contrast, others have reported that nonsurgical management is not associated with improvements in the severity of lameness.5
To our knowledge, information on the severity of lameness in cats with patellar luxation or grade of patellar luxation has not been published, nor have radiographic abnormalities in cats with patellar luxation been reported. The purposes of the study reported here, therefore, were to describe clinical signs, including severity of lameness, grade of patellar luxation, and radiographic abnormalities, in cats with patellar luxation and to report outcome following surgical and nonsurgical treatment.
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SAS, version 9.0, SAS Institute Inc, Cary, NC.
Smith GK, Langenbach A, Green PA, et al. Evaluation of the association between medial patellar luxation and hip dysplasia in cats. J Am Vet Med Assoc 1999;215:40–45.
Nunamaker DM. Patellar luxation. In: Nunamaker DM, ed. Textbook of small animal orthopedics. Philadelphia: JB Lippincott Co, 1985;946.
Roy RG, Wallace LJ, Johnston GR, et al. A retrospective evaluation of stifle osteoarthritis in dogs with bilateral medial patellar luxation and unilateral surgical repair. Vet Surg 1992;21:475–479.
Guthrie S. Use of radiographic scoring technique for the assessment of dogs with elbow osteochondrosis. J Small Anim Pract 1989;30:639–644.
Hayes AG, Boudrieau RJ, Hungerford LL. Frequency and distribution of medial and lateral patellar luxation in dogs: 124 cases (1982–1992). J Am Vet Med Assoc 1994;205:716–720.
Scavelli TD, Schrader SC. Nonsurgical management of rupture of the cranial cruciate ligament in 18 cats. J Am Anim Hosp Assoc 1987;23:337–340.