Septic Arthritis

Septic arthritis is an infection inside a joint. Bacteria or other organisms enter the joint space, triggering inflammation that can damage cartilage and bone if it persists. It tends to affect a single joint, though multiple joints can be involved in some cases. Owners often notice sudden lameness in one limb, reluctance to bear weight, and swelling or heat around the affected joint. The dog or cat may be quieter than usual, reluctant to move, or show signs of discomfort when the area is touched. These patterns can appear after a wound, a surgical procedure, or sometimes without an obvious external cause. This page explores the signals that may point towards septic arthritis, the mechanisms that allow infection to take hold in a joint, the investigations used to confirm the diagnosis and identify the organism involved, and the range of approaches used to manage it.