INTRODUCTION
In the adult horse, traumatic meniscal injuries result in lameness, and are amongst the commonly reported soft tissue injuries of the femorotibial joints (De Busscher et al. , 2006; Nemery et al. , 2016; Ribitsch et al. , 2018). There are relatively few documented cases of soft tissue injuries of the stifle in foals, including cases of popliteal tendonitis (Gabriel and Marta, 2020), an avulsion of the combined origin of the long digital extensor tendon and fibularis tertius from the extensor fossa (Blikslager and Bristol, 1994), a complete tear of the vastus medialis muscle with patellar luxation (Ogden et al. , 2019), and a complex stifle injury involving the medial meniscus and cranial cruciate ligaments (Santschiet al. , 2020). These lesions were believed to be traumatic in origin with no septic processes reported.
The stifle is a commonly-reported site for sepsis in foals (Wrightet al. , 2017; O’Brien et al. , 2021). Compared to other stifle compartments, sepsis of the lateral femorotibial joint (LFTJ) is relatively rare (Reeves, Trotter and Kainer, 1991; Vacek, Ford and Honnas, 1992; Hennessy et al. , 2012). It has been estimated that up to 1% of all foals, and 13% of those in neonatal intensive care, are affected by septic arthritis and osteomyelitis (McIlwraith, 1983; Martens, Auer and Carter, 1986; Richardson DW and Stewart S, no date). Neonates are susceptible to septic arthritis due to their immature immune systems (Richardson DW and Stewart S, no date). Partial or complete failure of passive transfer of immunity is a common risk factor for hematogenous spread leading to septic arthritis (Richardson DW and Stewart S, no date). Rapid growth of bones and joints is associated with an increased vascular supply, which is believed to facilitate infectious foci becoming established in the physes and surrounding structures (Firth, 1983; Richardson DW and Stewart S, no date). Septic arthritis is commonly divided into 3 broad categories (Richardson DW and Stewart S, no date). S-type infections, of the synovial fluid and membrane, are usually seen in very young neonates (Richardson DW and Stewart S, no date). E-type infections affect the epiphyseal bone adjacent to the articular cartilage, and typically present in older foals(Richardson DW and Stewart S, no date). Finally, P-types are mainly seen in older foals, involving the physes of long bones, and may extend to the joint capsule (Richardson DW and Stewart S, no date). One limitation of this classification system is the lack of inclusion of soft tissue structure involvement, aside from the joint capsule and synovial membrane.
To the authors’ knowledge, there have been no reports of meniscal involvement in cases of septic arthritis of the stifle of the foal. Furthermore, although septic arthritis associated with osteochondral lesions in the femoral condyle of the stifle joint has been reported, to date histopathological findings of such lesions is missing (Haggettet al. , 2012).
The objective of this short case series was to report the clinical characteristics, surgical management, histopathological findings and medium-term outcomes of 3 Arabian neonatal foals with meniscal disruption associated with septic arthritis of the LFTJ.