Patellar Luxation in the
Cavalier King Charles Spaniel


Cavalier King Charles spaniels may suffer from a recurring hereditary condition which causes luxating patellas -- loose knee caps. The disorder is believed to affect as many as 20% of cavaliers. The patella is the dog's knee cap. It should be located in its groove in the center of the stifle (knee joint) of the femur (upper leg bone). A luxating patella is a knee cap that moves out of its groove. It also may be called a floating kneecap. Genetic conditions which cause patellar luxation are a shallow groove, weak ligaments, and misalignment of the muscles and ligaments between the femur, patella, and tibia (lower leg bone).

If the condition is not corrected, it will degenerate: the patella's ridges will wear, its groove will become shallower, and the cavalier will become progressively more lame. Arthritis will prematurely affect the joint, causing a permanently swollen knee with poor mobility.

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Symptoms & Diagnosis

Veterinarians can check for patellar luxation by manipulating it. The dog is examined awake and the veterinarian classifies its degree of luxation. Adult cavaliers should be evaluated annually, and puppies should be examined at 6-8 weeks of age prior to their release to the new owners.

The Orthopedic Foundation for Animals (OFA) has a diagnosis protocol and registration for examining dogs for patellar luxation.

Grades of Patellar Luxation

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Treatment

-- medications

Dogs with milder grades of luxation often are prescribed non-steroidal anti-inflammatory drugs (NSAIDs), such as such as carprofen* (Rimadyl, Quellin), meloxicam (Metacam), firocoxib (Previcox), mavacoxib (Trocoxil), deramaxx (Deracoxib), and aspirin** to relieve the pain but not any but not the deterioration. NSAIDs should not be administered without supervision by a veterinarian. The US Food & Drug Administration (FDA) warns about the dangers of using NSAIDs here on its website.

*Carprofen (Rimadyl, Quellin) may have serious side effects and should not be given without a veterinarian's close guidance and monitoring.
**Aspirin may also have serious side effects and should not be given without a veterinarian's close guidance and monitoring.

-- surgery

Veterinary orthopedic surgery usually is required to correct more severe stages of the condition, such as Patella SurgeryGrade 3 or 4. The groove may be surgically deepened to better contain the patella. The patella itself may be tied down laterally (on its outside), to prevent it from deviating medially (toward the inside). The bony protuberance at the point the quadriceps tendon attaches to the tibia may be cut off and then re-attached in a more lateral position.

Recovery from patella surgery includes a lot of downtime, resting in a crate, with very limited physical activity, for as long as the surgeon recommends.

Water therapy after knee surgery-- alternative therapies

In some cases, non-traditional therapies such as holistic healing or homeopathy, including acupuncture, and joint supplements such as Glyco-Flex II by VetriScience, may be useful alternatives to conventional medicine and surgery. Some physical therapy, such as hydrotherapy (swimming) (right), may also be prescribed. Dogs with patellar luxation should not be over-weight.

See also Dr. Karen Becker's webpage on "3 things to avoid knee surgery".


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Canine Patella DiagramBreeders' Responsibilities

The Canine Inherited Disorders Database recommends that any dogs with patellar luxation not be bred, nor should their parents or littermates. Because of the strong hereditary relationship, all cavalier King Charles spaniel breeding stock should be examined by qualified veterinarians at least annually and cleared for patellar luxation, the closer the examination to the breeding the better.

The Cavalier King Charles Spaniel Club, USA (CKCSC,USA) recommends that, prior to breeding any cavalier, the dog have no evidence of patellar luxation from an evaluation by a licensed veterinarian.  The American Cavalier King Charles Spaniel Club (ACKCSC) states that "Cavaliers used for breeding should have within normal limits patellas as determined by an OFA examination at age one. The patellas should be reevaluated as the Cavalier ages."

The Canine Health Information Center (CHIC) is a centralized canine health database sponsored by the AKC/Canine Health Foundation (AKC/CHF) and OFA. The CHIC, working with participating parent clubs, provides a resource for breeders and owners of purebred dogs to research and maintain information on the health issues prevalent in specific breeds.

AKC's national breed clubs establish the breed specific testing protocols. Dogs complying with the breed specific testing requirements are issued CHIC numbers. The ACKCSC requires that, to qualify for CHIC certification, cavaliers must be screened for patellar luxation (OFA).

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Research News

August 2016: Cavaliers were 10% of 5-year study of bilateral surgeries for patellar luxation. In an August 2016 article, veterinary surgeons (Javier Gallegos [left], Marcos Unis, James K. Roush, Lori Javier Gallegos, DVMAgulian) studied the results of 50 single-session bilateral corrective surgeries for congenital medial patellar luxations. Five of the 50 dogs were cavalier King Charles spaniels (CKCS). All dogs were under 33 lbs. Of 11 dogs with post-operative complications, one was a CKCS. The surgeries were performed at the Kansas State University's veterinary school and at a Fountain Valley, California VCA referral center. The authors concluded that:

"Single-session bilateral corrective surgery for MPL [medial patellar luxation] is well tolerated in small dogs with complication rates historically similar to dogs undergoing unilateral or staged bilateral surgery. With individual case assessment, single-session surgery could be offered to owners, allowing one anesthetic episode and potentially lowering the chance for morbidity. Further studies, ideally prospective studies, are needed to assess long-term outcome following single-session bilateral corrective surgery for MPL."

CKCS with medial patellar luxationMarch 2016: UK orthopods report CKCSs are over-represented for medial patella luxation. In a March 2016 article, UK veterinary orthopedists (Albane Fauron, Karen Perry) report that cavalier King Charles spaniels are "consistently over-represented" for medial patella luxation. In their article, they summarize the pathophysiology and diagnosis of patella luxation (PL) and use one of their cavalier patients (at right) as an example of a dog affected with the medial version (near the mid-line of the knee) of PL.


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Related Links

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Veterinary Resources

Patellar luxation in the dog and cat. John Ferguson. In Practice. April 1997;19(4):174-184. Quote: "Patellar luxation is a commonly seen orthopaedic problem in veterinary practice. Diagnosis of the condition is usually straightforward. However, a knowledge of the normal anatomy, function and interrelationship between the hip and stifle joints, femur, tibia and soft tissues is necessary if the surgeon is to choose the most appropriate method of treatment. This article describes medial and lateral patellar luxation, the clinical signs, diagnosis and treatment options available in the dog and cat. ... . Cavalier King Charles spaniel: a breed with a high incidence of patellar luxation."

Control of Canine Genetic Diseases.  Padgett, G.A., Howell Book House 1998, pp. 198-199, 246.

Guide to Congenital and Heritable Disorders in Dogs.  Dodds WJ, Hall S, Inks K, A.V.A.R., Jan 2004, Section II(235).

Complications Associated with Corrective Surgery for Patellar Luxation in 109 Dogs. Gareth I. Arthurs and Sorrel J. Langley-Hobbs. Vet. Surg. Aug 2006; 35:559.

Patellar luxation. Greg Harasen. Can Vet J. 2006 August; 47(8): 817–818. Quote: "Congenital luxation of the patella represents one of the most common orthopedic conditions in small animal practice. Medial luxations account for 75% to 80% of cases in all breeds. The majority of patients are small breed dogs including ... cavalier King Charles spaniels. ... The overwhelming majority of patellar luxation are congenital and certainly hereditary, although a mode of inheritance has not been described."

Diagnostic and genetic aspects of patellar luxation in small and miniature breed dogs in Austria. B. Vidoni, I. Sommerfeld-Stur, E. Eisenmenger. European J. of Companion Anim. Pract. October 2006;16(2):149-158. Quote: During a period of eight years (1996 – 2004) 432 small and miniature breed dogs were screened for patellar luxation (PL). In order to achieve the diagnostic accuracy required for genetic screening to assist breeding programmes, examinations were based on the concept of a standardized examination protocol for patellar luxtion. Diagnostic criteria assessed by physical examination, inspection and palpation focussed on lameness, evaluation of patellar tracking in the standing and recumbent position, with special focus on patello-femoral instability, as well as on the deviation of the tibial tuberosity and any perceivable crepitation of the stifle joint during manipulation. Evaluation of all findings was made on the basis of PUTNAM´s (1968) classification. Radiographic examinations were not performed. Patellar luxation (unilateral or bilateral, medial and/or lateral) was diagnosed in 61.6 % of the examined dogs, but permanent lameness was only present in 15.5 % (right stifl e) and 12.8 % (left stifl e), respectively. Intermittent lameness was observed in only 3.5 % (right stifle) and 4.6 % (left stifle), respectively. This means that almost 40 % of all dogs with patellar luxation are asymptomatic and their condition would not have been detected without diagnostic screening. The different diagnostic criteria showed signifi cant correlation between each other and with the final findings. In some parameters like “luxation in standing position“ and “luxation in recumbent position“, the correlation with fi nal fi ndings was particularly high. Thus, the examination protocol used in this study appears to be suitable for PL screenings in dogs. Investigation of the influence of parameters like body weight, age, gender and neutering on the presence of PL showed that, except for gender, all attributes were associated with the occurrence of PL. An increase in body weight of 1 kg decreased the odds of suffering from PL to the 0.8fold (p<0.05), while an increase of age of one year increased the odds to the 1.1 fold (p<0.051). For neutered dogs, the odds showed a 3.1 fold increase of being affected by PL (p<0.05). No signifi cant infl uence could be observed for the gender of the animals. In order to detect breed predispositions for patellar luxation, odds ratios were calculated for all breeds represented in the study by more than ten animals. The breeds involved were: Jack Russell Terrier, Pug, Papillon, Pekingese, Shih Tzu, Tibet Terrier, West Highland White Terrier, Poodle, Yorkshire Terrier, Maltese Terrier and Chihuahua. [Cavalier King Charles spaniels were included in the "Other Breeds" category.] Only two breeds showed odds ratios that were significantly different from 1: In the Jack Russell Terrier, the odds ratio was signifi cantly lower (0.31) (95 % confidence intervals 0.14-0.67), while the odds ratio was significantly increased (5.62) in Poodles (Miniature and Toy Poodles) (95 % confi dence intervals 1.93-16.41). This means that Jack Russell Terriers have a comparatively reduced risk of suffering from PL, while the chance to develop the condition seems increased in Poodles. These results are highly indicative of a genetic background but further investigation on the basis of familial anamneses and heritability studies is required to support this postulate. A standardized examination technique and offi cial validation of the PL screening tests represent an essential precondition for the acceptance of PL screening programmes by breeders. Based on the results of this study, it is strongly recommended to implement a uniform, internationally valid and highly accurate diagnostic screening programme for patellar luxation. At the moment, this screening protocol is used by veterinarians in Germany, Switzerland and Austria.

Frequency and distribution of patellar luxation in dogs. 134 cases (2000 to 2005). M R Alam, J I Lee, H S Kang, I S Kim, S Y Park, K C Lee, N S Kim. Vet. & Comparative Ortho & Traum. January 2007;20(1):59-64. Quote: "This study investigated the frequency and distribution of patellar luxation in the dogs presented to the Chonbuk National University Animal Medical Centre during January 2000 to September 2005. Patellar luxations were classified as medial or lateral, and unilateral or bilateral, were graded I to IV, and were subdivided according to age, sex and size of the dogs. The incidence of medial patellar luxation (MPL) was greater than the incidence of lateral patellar luxation (LPL) in both small and large dogs. Small-breed dogs were admitted almost exclusively with MPL. LPL was found uncommon; however it was observed more often in larger-breed dogs. Surgical correction was performed primarily in the dogs (165 stifles in 111 dogs) with grade II, III and IV patellar luxations following different surgical techniques. The combination of the surgical techniques was found to be more effective for the management of the disease. The prognosis was found to be favourable, because when the grade was low, the dog was younger, without cruciate ligament rupture, and as the surgical correction was performed with combination of more techniques."

The prevalence of canine patellar luxation in three centres. Clinical features and radiographic evidence of limb deviation. N. Bound; D Zakai; S. J. Butterworth; M. Pead. Vet.Comp.Orthop.Traumatol. Jan. 2009. Quote: "The medical records of 155 dogs with patellar luxation (PL) from three different centres were analysed. [Cavalier King Charles spaniels were the second most common. See Figure 3 of the article.] Each case was classified according to the nature of its luxation and any concurrent orthopaedic conditions plus the age at diagnosis were also noted. Measurements relating to angle of inclination (AOI) of the femoral neck and medio-lateral bowing of the femur and tibia at the stifle were also recorded. The femoral and tibial data were compared to dogs with another orthopaedic condition in a case-control assessment. Labradors were most commonly affected (21%). Most luxations were medial (92%) and 54% of affected dogs were female. The mean AOI of the hip was 148.95°. There was a statistically significant difference between the stifles of dogs with PL compared to a control population. This study concluded that PL in large breeds is increasing. Lateral luxation was uncommon and was not associated exclusively with large breeds. Females were more likely to have PL than males and being female was a risk factor associated with coxa valga. There are significant differences in medio-lateral stifle conformation between dogs with PL and control dogs."

Breed Predispositions to Disease in Dogs & Cats (2d Ed.). Alex Gough, Alison Thomas. 2010; Blackwell Publ. 52.

Surgical treatment of medial patellar luxation without femoral trochlear groove deepening procedures in dogs: 91 cases (1998–2009). William R. Linney,Douglas L. Hammer, Susan Shott. J Am Vet Med Assoc. 2011;238:1168–117. Quote: "Objective: To assess signalment, outcomes, and complications for dogs surgically treated for medial patellar luxation (MPL) with a combination of lateral retinacular imbrication and tibial crest transposition procedures without femoral trochlear groove deepening techniques, and to determine whether osteoarthritis progressed in these patients during the 8-week period following surgery. Design: Retrospective case series. Animals: 91 dogs. ... The most commonly represented breed was mixed, followed by Cavalier King Charles Spaniel ... Procedures: Medical records were reviewed for information on signalment, clinical history, unilateral versus bilateral disease, preoperative and postoperative MPL grades, duration of follow-up, and perioperative and postoperative complications. Radiographs obtained preoperatively and during 8-week follow-up examinations were reviewed and assigned degenerative joint disease (DJD) scores (range, 0 to 3). Data were analyzed to determine factors influencing outcomes. Kaplan-Meier curves were constructed for recurrence of MPL. Results: Minor postoperative complications were reported for 31 of 91 (34.1%) dogs. Patellar reluxation occurred in 18 of 91 (19.8%) dogs. Reluxation or complications for which additional surgery was recommended developed in 6 of 91 (6.6%) dogs. At last clinical follow-up, 10 of 91 (11.0%) dogs had at least occasional lameness. No difference was revealed between preoperative and postoperative (8-week follow-up) radiographic DJD scores. Conclusions and Clinical Relevance: Results of surgical treatment of MPL without femoral trochlear groove deepening procedures were comparable to those in studies of surgical treatment that included groove deepening procedures. Radiographic indices of DJD did not increase during the 8 weeks following surgery. These results suggest that trochlear groove deepening procedures are not always necessary, and patients that undergo these techniques should be carefully selected."

Genetic Connection: A Guide to Health Problems in Purebred Dogs, Second Edition. Lowell Ackerman. July 2011; AAHA Press; pg 134. Quote: "Table 9.10 -- Breeds at Risk for Patellar Luxation on the Basis of a Large-Scale Epidemiologic Study: ... 8. Cavalier King Charles spaniel -- odds ratio 9.1."

Genome-wide survey indicates involvement of loci on canine chromosomes 7 and 31 in patellar luxation in flat-coated retrievers. Ineke C Lavrijsen, Peter A Leegwater, Chalika Wangdee, Frank G. van Steenbeek, Monique Schwencke, Gert J. Breur, Freek J. Meutstege, Isaac J. Nijman, Edwin Cuppen, Henri C. Heuven, Herman A. Hazewinkel. BMC Genetics. May 2014. Quote: "Background: Patellar luxation is an orthopedic disorder in which the patella moves out of its normal location within the femoral trochlea of the knee and it can lead to osteoarthritis, lameness, and pain. In dogs it is a heritable trait, with both environmental and genetic factors contributing to the phenotype. The prevalence of patellar luxation in the Dutch Flat-Coated Retriever population is 24%. In this study, we investigated the molecular genetics of the disorder in this population. Results: Genome-wide association analysis of 15,823 single nucleotide polymorphisms (SNPs) in 45 cases and 40 controls revealed that patellar luxation was significantly associated with a region on chromosome CFA07, and possibly with regions on CFA03, CFA31, and CFA36. The exons of the genes in these regions, 0,5 Mb combined, were analyzed further. These exons from 15 cases and a pooled sample from 15 controls were enriched using custom genomic hybridization arrays and analyzed by massive parallel DNA sequencing. In total 7257 variations were detected. Subsequently, a selection of 144 of these SNPs were genotyped in 95 Flat-Coated Retrievers. Nine SNPs, in eight genes on CFA07 and CFA31, were associated with patellar luxation (P <10-4). Genotyping of these SNPs in samples from a variety of breeds revealed that the disease-associated allele of one synonymous SNP in a pseudogene of FMO6 was unique to Flat-Coated Retrievers. Conclusion: Genome-wide association analysis followed by targeted DNA sequencing identified loci on chromosomes 7 and 31 as being involved in patellar luxation in the Flat-Coated Retriever breed."

Corrective surgery for canine patellar luxation in 75 cases (107 limbs): landmark for block recession. Mitsuhiro Isaka, Masahiko Befu, Nami Matsubara, Mayuko Ishikawa, Yurie Arase, Toshiyuki Tsuyama, Akiko Doi, Shinichi Namba. Vet.Sci.Development. May 2014;4(1). Quote: "Canine medial patellar luxation (MPL) is a very common orthopedic disease in small animals. Because the pathophysiology of this disease involves various pathways, the surgical techniques and results vary according to the veterinarian. Further, the landmark for block recession is not completely clear. We retrospectively evaluated 75 dogs (107 limbs) with MPL in whom our landmark for block recession was used from July 2008 to May 2013. Information regarding the breed, age, sex, body weight, body condition score (BCS), lateral vs. bilateral, pre-operative grading, surgical techniques, removal of implants, concomitance with anterior cruciciate ligament (ACL) rupture, re-luxation, re-operation, and rehabilitation was obtained from the medical records. The breeds were as follows: Chihuahua (n=23), Pomeranian (n=12), Yorkshire Terrier (n=9), and so on [2 cavalier King Charles spaniels with 3 limbs]. The study group consisted of 33 males (castrated n=13) and 42 females (spayed n=21). The median age was 53.3±35.9 months old (32-146 months); 13 cases were less than 12 months of age (17.3%). The pre-surgical BCSs were as follows: 1(n=0), 2(n=20), 3(n=24), 4(n=24) and 5(n=7). The body weight was 4.51±3.48kg (1.34-23.0kg); 71 cases (94.7%) were less than 10 kg. The MPL grades (each limb) were G1 (n=1), G2 (n=18), G3 (n=78), and G4 (n=10); 32 cases were bilateral and 43 cases were unilateral (right n=27; left n=16). The specific surgical procedure (distal femoral osteotomy) was 3 stifles in Chihuahuas. Concurrent with ACL rupture was 16/107 stifles (15.0%) corrected with the over-the-top method or the extracapsular method in Papillons (5/6), Chihuahuas (5/23), and so on. The occurrences of re-luxation and re-operation were 3 out of 107 stifles (2.8%) and 0%, respectively. In this retrospective study, we present a potentially good surgical landmark for block recession of MPL in dogs."

Canine patellar luxation part 1: pathophysiology and diagnosis. Albane Fauron, Karen Perry. Vet. Times. March 2016. CKCS with medial patellar luxationQuote: "Patellar luxation (PL) is a commonly diagnosed canine orthopaedic condition and, in the majority of dogs, is a developmental condition, as opposed to a traumatic one, resulting from skeletal abnormalities. ... The Orthopaedic Foundation for Animals (OFA) named Pomeranians as the highest incidence of PL, with 37.2% of dogs affected during an evaluation lasting from January 1974 to December 2014 (OFA, 2014). Chihuahuas, poodles, Maltese terriers, cavalier King Charles spaniels and Yorkshire terriers are also consistently over-represented across different studies. ... This figure [at right] shows ... a cavalier King Charles spaniel that presented with grade II MPL [medial patellar luxation]. ... Medial patellar luxation (MPL) is the most common form of PL in dogs of all sizes. Lateral patellar luxation is less frequent and reported to occur more often in medium to large breed dogs. Luxations are graded on a four-point scale. Diagnosis is based on the clinical presentation and thorough orthopaedic examination. Concomitance of cranial cruciate ligament (CrCL) pathology has been reported in 13% to 25% of dogs presenting for MPL and the integrity of the CrCL should be systemically assessed in these cases. Although radiology is not required for a diagnosis, it remains critical in the identification of any underlying skeletal abnormalities.

Outcome Following Surgical Correction of Grade 4 Medial Patellar Luxation in Dogs: 47 Stifles (2001–2012). Eric C. Hans, Sharon C. Kerwin, Alan C. Elliott, Ryan Butler, W. Brian Saunders, Don A. Hulse. J. Amer. Anim. Hosp. Assn. March 2016. Quote: "Grade 4/4 medial patellar luxation (MPL) is a complex disease of the canine stifle that often requires surgical realignment of the patella to resolve clinical lameness. Outcome following surgery remains poorly described. Medical records were retrospectively reviewed for surgical correction of grade 4 MPL. Signalment and exam findings, surgical procedures performed, complications, and clinical outcome were reported. Data was statistically analyzed for association with major complication occurrence and unacceptable function following surgery. Forty-seven stifles from 41 dogs were included. ... Cavalier King Charles spaniels (n=3) ... The surgical procedures most frequently utilized for patellar realignment were the combination of femoral trochleoplasty, tibial tuberosity transposition, and joint capsule modification. Median in-hospital veterinary examination was performed at 69 days (range 30–179 days) following surgery. Full function was reported for 42.6% of cases (n=20). Acceptable function was reported for 40.4% of cases (n=19). Unacceptable function was reported for 17% of cases (n=8). The overall complication rate was 25.5% (n=12), with revision surgery for major complications required in 12.8% of cases (n=6). Corrective osteotomies were associated with major complications (P < 0.001). In general, pelvic limb function improves following surgical correction of grade 4 MPL; however, a return to full function should be considered guarded."

The epidemiology of patellar luxation in dogs attending primary-care veterinary practices in England. O’Neill D, Meeson R, Sheridan A, Church D, Brodbelt D. Canine Genetics & Epidemiology. June 2016;3:4. Quote: Background: Canine patellar luxation is one of the most common orthopaedic disorders of dogs and is a potential welfare concern because it can lead to lameness, osteoarthritis and pain. However, there are limited epidemiological data on the disorder relating to the general population of dogs in England. This study aimed to investigate the VetCompass Programme database of dogs attending primary-care veterinary practices in England to report on the prevalence, risk factors and clinical management of diagnosed patellar luxation cases. Results: The study included all dogs with at least one electronic patient record in the VetCompass database from September 1st, 2009 to August 31st, 2014. Candidate patellar luxation cases were identified using free-text word searching of the clinical notes and VeNom diagnosis term fields. Univariable and multivariable binary logistic regression modelling was used for risk factor analysis. The overall dataset comprised 210,824 dogs attending 119 clinics in England. The prevalence of patellar luxation diagnosis in dogs was 1.30% (95% confidence interval (CI) 1.21–1.39). Of the 751 incident cases, 293 (39.0%) received medical management, 99 (13.2 %) received surgical intervention and 28 (3.7%) were referred for further management. Multivariable modelling documented 11 breeds with increased odds of patellar luxation compared with crossbred dogs, including the Pomeranian (odds ratio [OR]: 6.5, 95% CI 4.0–10.7, P <0.001), Chihuahua (OR: 5.9, 95% CI 4.4–7.9, P <0.001), Yorkshire Terrier (OR: 5.5, 95% CI 4.3–7.1, P <0.001) and French Bulldog (OR: 5.4, 95% CI 3.1–9.3, P <0.001). ... Cavalier King Charles Spaniel (OR: 2.5, 95% CI 1.8–3.5, P <0.001). ... Dogs aged ≥12.0 years showed 0.4 times the odds (95 % CI 0.3–0.5, P <0.001) compared with dogs aged <3.0 years. Females had 1.3 times the odds (95 % CI 1.1–1.5, P <0.001), neutered dogs had 2.4 times the odds (95 % CI 1.8–3.2, P <0.001) and insured dogs had 1.9 times the odds (95 % CI 1.6–2.3, P <0.001). Conclusions: Patellar luxation warrants inclusion as a welfare priority in dogs and control strategies that include this disorder should be considered as worthwhile breeding goals, especially in predisposed breeds.

Postoperative Complications and Short-Term Outcome Following Single-Session Bilateral Corrective Surgery for Medial Patellar Luxation in Dogs Weighing <15 kg: 50 Cases (2009–2014). Javier Gallegos, Marcos Unis, James K. Roush, Lori Agulian. Vet. Surgery. August 2016. Quote: Objective: To assess complication rates and short-term outcome in small dogs with bilateral medial patellar luxation (MPL) undergoing single-session bilateral corrective surgery. Study Design: Retrospective case series. Animals: Dogs weighing <15 kg with congenital bilateral MPL that underwent single-session bilateral corrective surgery (n=50) [including 5 cavalier King Charles spaniels]. Methods: Surgical procedures for MPL correction included trochlear wedge recession (TWR), crest transposition, lateral imbrication, and medial fascial release. Complication rates were correlated with number of surgical procedures, weight, whether or not a bandage was applied postoperatively, and surgeon experience (ACVS Diplomate vs resident). Results were compared with the most recent study evaluating single-session bilateral corrective surgery for MPL. Results: Overall complication rate was 22% (11 of 50 dogs) [including 1 cavalier]. Implant failure occurred in 2 dogs (3 stifles) requiring revision. Grade 1 patella reluxation was the most common minor complication at 10% (5/50). Overall complication and reluxation rates were similar to previous studies. There were no intraoperative complications after performing TWR in small dogs. Conclusion: Single-session bilateral corrective surgery for MPL is well tolerated in small dogs with complication rates historically similar to dogs undergoing unilateral or staged bilateral surgery. With individual case assessment, single-session surgery could be offered to owners, allowing one anesthetic episode and potentially lowering the chance for morbidity. Further studies, ideally prospective studies, are needed to assess long-term outcome following single-session bilateral corrective surgery for MPL.

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