Non-Autoimmune Arthritis

Septic arthritis is an infection of the joint due to direct inoculation, contiguous extension, or hematogenous spread of infectious organisms into the joint space. This process causes an acute, inflammatory, monoarticular arthritis. A variety of organisms have been implicated, most commonly Staphylococcus aureus. Previously damaged joints (e.g., rheumatoid arthritis) are at the highest risk of infection. Patients present with a swollen, warm, and tender joint, most commonly involving the knee. Positive cultures from arthrocentesis are diagnostic, with antibiotic therapy tailored to the specific organism. Repeated joint aspiration, or surgical drainage, is required in some cases. If the joint space is infected with a prosthetic in place, debridement and prosthesis removal may also be required.

Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Physical exam may reveal crepitus with joint motion and osteophyte formation (Heberden's and Bouchard's nodes). The diagnosis is clinical and supported with radiographic joint findings. Management includes conservative measures, analgesic medications, glucocorticoid intra-articular injections, and surgery for advanced disease.

Gout is a heterogeneous metabolic disease associated with elevated serum uric acid levels (> 6.8 mg/dL) and abnormal deposits of monosodium urate in tissues. The condition is often familial and is initially characterized by painful, recurring, and usually monoarticular acute arthritis, or “gout flare,” followed later by chronic deforming arthritis. The kidneys can also be affected, and urate crystals can precipitate as chalkstone-like deposits (“tophi”) in the soft tissues, synovial tissues, or in bones near the joints. Hyperuricemia is due to overproduction and/or underexcretion of uric acid and is a necessary but insufficient precondition to developing urate crystal deposition disease (most hyperuricemic individuals never experience clinical gout). The most commonly involved joint is the first metatarsophalangeal joint. The identification of urate crystals in joint aspirate or tophi is diagnostic. Effective therapies to relieve the pain of a gout flare include nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, and glucocorticoids; the choice of therapy depends on the individual and if there are any contraindications.