Equine Arthritis: Septic and Non-Septic – NAVLE Study Guide

Overview and Clinical Importance

Arthritis in horses encompasses a spectrum of inflammatory joint diseases that significantly impact equine health, performance, and welfare. Understanding the distinction between septic (infectious) arthritis and non-septic arthritis (including osteoarthritis/degenerative joint disease) is critical for NAVLE success. Septic arthritis represents a true veterinary emergency requiring immediate intervention, while osteoarthritis (OA) accounts for approximately 60% of all equine lameness cases and is the leading cause of poor performance in athletic horses.

Part 1: Septic Arthritis

Definition and Pathophysiology

Septic arthritis (SA) is a joint infection caused by bacterial invasion of the synovial space. It represents a potentially life-threatening or career-ending emergency requiring immediate veterinary attention. The synovial membrane is highly susceptible to infection because it lacks a basement membrane, allowing rapid bacterial colonization.

Pathophysiologic Cascade: Bacterial invasion triggers an inflammatory response with release of cytokines (IL-1, TNF-alpha) and degradative enzymes (matrix metalloproteinases). This leads to synovial membrane inflammation, fibrin accumulation, cartilage degradation, and potentially subchondral bone destruction. Without treatment, irreversible cartilage damage can occur within 24-48 hours.