Diagnosis

We concluded this foal has localized septic arthritis due to trauma.  The organism is Klebsiella , which most likely gained entry into the joint through a puncture wound. Horses are particularly susceptible to this because of the minimal soft tissue covering over joints.   Septic arthritis usually presents as mild to moderate lameness, with inflammation shown in this patient by swelling and pitting edema.

The joint pain and swelling is due to the influx of immune mediators.  These immune mediators cause the neutrophils and fluid to enter the joint and increase the pressure on joint capsule nerves and cause the pain and associated lameness. 

The prognosis is good with correct antibiotic therapy the infection and associated inflammation should be resolved.  The prognosis is better due to the fact that the infection was hopefully diagnosed before could cause permanent damage to the articular cartilage and synovial membranes.