Septic arthritis is an acute suppurative arthritis of the dog characterised by infection with bacteria, viruses, fungi or other infectious agents.
Septic arthritis occurs with higher frequency in large breed dogs, twice as often in males as in females and there is no age predisposition.
It usually appears as an acute onset joint swelling with heat, pain, fever and lameness observed clinically. Depending on the inciting cause, systemic illness may be associated with the condition such as lethargy, toxemia, endocarditis and icterus.
Primary initiation is usually through trauma, penetrating foreign bodies (sticks, awns, quills, etc) or post-operative infections, but hematogenous spread can occur, especially in young, or debilitated dogs. As the disease progresses, the joint space becomes distended with exudate which may be observed radiographically. This is inexorably followed, without intervention, by subluxation, destructive arthritis and vascular compromise to the epiphysis.
Bacteria are commonly involved, including Streptococcus pyogenes, Staphylococcus aureus, Pasteurella spp, Klebsiella spp and Chlamydophila spp, but fungi (e.g. Blastomyces dermatitidis), viruses (e.g. canine distemper virus) and even aberrant nematode migrations (Dirofilaria immitis) have been reported.
Diagnosis requires aseptic aspiration of joint fluid, which is usually serosanguinous. Cultures are not always rewarding but the presence of toxic, degranulated, or ruptured neutrophils should strongly suggest an infectious etiology.
A leucocytosis is usually evident on blood sampling and hematological analysis.
Septic arthritis occurs less frequently than immune-mediated arthritis, but may be difficult to differentiate clinically. Septic arthritis most often affects only one or two joints, while immune-mediated arthritis usually affects many joints.
Treatment usually requires arthroscopic or exploratory curettage and lavage of the affected joint, if possible, augmented with parenteral broad-spectrum antimicrobial drugs such as enrofloxacin, clindamycin, amoxycillin/clavulanate or gentamycin.
These infectious should be treated aggressive to eliminate persistent and recurrent infections, thus avoiding permanent lameness, particularly in young dogs.
In most cases, the response to immediate medical and surgical intervention is good, but diminution of full joint function is common.
- Uni of Pennsylvania
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