Periprosthetic Joint Infection (PJI) is an infection that occurs around a joint replacement implant, such as a hip or knee replacement. It happens when bacteria enter the area around the artificial joint, leading to pain, swelling, and difficulty moving the joint. Persistent pain in the replaced joint. Swelling, redness, or warmth around the joint. 🔹 Fluid leakage (drainage) from the wound. Fever or chills (in some cases). Difficulty moving the joint or feeling unstable.