Canine patellar luxation (PL) is one of the most common orthopedic disorders of the stifle joint that causes chronic lameness, pain, and development of degenerative joint diseases (Pinna et al., 2013; O'Neill et al., 2016; Bosio et al., 2017; Tuek-Um et al., 2023). Dislocation of the patella from the trochlear groove causes stifle joint instability and may predispose cranial cruciate ligament injury (Nganvongpanit and Yano, 2011; Fauron et al., 2017; Candela Andrade et al., 2022). Engdahl et al. (2023) found that 6.20% of dogs with PL showed concomitant impacts of cranial cruciate ligament rupture. Medial luxation was more common than other types of luxation in 75–80% of all breeds (Bosio et al., 2017). Most cases of medial PL are diagnosed in small dog breeds including Pomeranians, Chihuahuas, Toy poodles, and Yorkshire terriers (Maeda et al., 2019; Mizutani et al., 2023). Lateral PL is less common and generally found in large dog breeds, particularly St. Bernards (Kalff et al., 2014). PL is classified as congenital, developmental, or traumatic depending on the etiology and onset of the disease with most cases classified as developmental because they develop during skeletal growth without any history of trauma (Nagahiro et al., 2023). The pathogenesis of PL remains unclear (Di Dona et al., 2018).
A physical examination is required to grade the extent of PL. Radiography is a necessary tool to identify the severity of skeletal deformity and the degree of degenerative changes presenting in the stifle joint, and also to decide on the appropriate method of treatment (Serra et al., 2021; Jung et al., 2023). Anatomical abnormalities associated with PL includes dislocation of the quadriceps muscle group, deformity of the distal femur and the proximal tibia, and femoral epiphyseal hypoplasia (de Moya et al., 2020; Nagahiro et al., 2020; Feldmane and Theyse, 2021; Lehmann et al., 2021; Murakami et al., 2021; Perry and Dejardin, 2021; Yasukawa et al., 2021). The management of PL in dogs involves conservative or surgical treatments depending on the grade (Di Dona et al., 2018). Most dogs with grades I and II PL, having mild and infrequent lameness can be managed by anti-inflammatory drugs (NSAIDs), weight control, joint supplements, and physical rehabilitation (Di Dona et al., 2018; Hamilton et al., 2020). Dogs with grades III and IV who suffer from intermittent or permanent lameness are recommended to undergo surgery (Souza et al., 2010; Jervan et al., 2020). A retrospective study by Hamilton et al. (2020) reported that 50% of dogs with grade II PL subsequently developed chronic lameness and required surgical treatment. Surgery restores normal alignment of the quadriceps muscle and repositions the patella within the deepening trochlear groove (Rossanese et al., 2019), and a combination of osseous and soft tissue surgical techniques is required in most cases to restore stifle joint stability (Candela Andrade et al., 2020). The most common postoperative problems are reluxation and implant-associated complications (Di Dona et al., 2018; Rossanese et al., 2019; DiGiovanni et al., 2023). The prognosis is favorable if severe cartilage erosion of the femoral trochlear or the development of secondary osteoarthritis is not present (Daems et al., 2009; Lara et al., 2018). PL impacts the welfare of dogs, and 52.60% of affected dogs with median age 2.20 years were euthanized (Engdahl et al., 2023).
Many studies have addressed the prevalence of PL, O'Neill et al. (2016) reported 1.30% of dogs with developmental orthopedic diseases in England, with 5.40% in the USA (LaFond et al., 2022), and the overall prevalence of PL in Italy from 2009 to 2014 was 9.20% (Bosio et al., 2017). In Thailand, the prevalence of PL in dogs in Bangkok was studied by Wangdee et al, (2005) and Soontornvipart et al., (2013), and in Chiang Mai by Nganvongpanit and Yano (2011). The prevalence of medial PL and lateral PL from 2006 to 2008 in Bangkok was 87% and 13%, respectively in small dog breeds, especially Pomeranian, while in Chiang Mai from 2006 to 2011, PL was most commonly found among Poodles (34.30%). Garces et al. (2021) showed that mixed and large dog breeds had the lowest risk of PL. However, no published research exists on PL frequency in Southern Thailand. This study assessed the prevalence of PL in Southern Thailand and evaluated the risk factors to assist in the prevention and control of the disease.