Septic arthritis is a serious medical condition where a joint becomes infected by bacteria or other microorganisms, causing inflammation inside the joint space. This infection can happen in any joint but most commonly affects large joints like the knee, hip, or shoulder. The infection leads to swelling, intense pain, warmth, and redness around the joint, often accompanied by fever and a reduced ability to move the joint. It is considered a medical emergency because the infection can rapidly destroy the cartilage and other joint structures, potentially leading to permanent joint damage or disability if not treated promptly.
The infection usually reaches the joint through the bloodstream, which is the most common route, especially when bacteria from another part of the body enter the blood and settle in the joint. It can also occur through direct contamination, such as from a penetrating injury, surgery, or injections into the joint. Sometimes, the infection spreads from nearby infected tissues like bones or soft tissues adjacent to the joint.
Certain people are at higher risk of developing septic arthritis. These include individuals with pre-existing joint diseases like rheumatoid arthritis, those with weakened immune systems, people who have prosthetic joints, and those who have recently had joint surgery or injections. Trauma to the joint or skin infections near the joint can also increase the risk.
When septic arthritis develops, the joint becomes acutely swollen, very painful, and warm to the touch. The pain is often severe enough to limit any movement of the joint. Fever and chills are common systemic signs of infection. Because the infection can quickly damage the cartilage that cushions the bones, early diagnosis and treatment are critical to prevent permanent joint destruction.
Diagnosis typically involves taking a sample of the joint fluid through a procedure called arthrocentesis. This fluid is analyzed for the presence of bacteria, white blood cells, and other markers of infection. Blood tests and imaging studies like X-rays or ultrasound may also be used to assess the extent of infection and joint damage.
Treatment requires urgent administration of antibiotics to kill the infecting bacteria. Initially, broad-spectrum antibiotics are given until the specific bacteria are identified from the joint fluid culture, after which treatment is tailored accordingly. In many cases, repeated drainage of the infected joint fluid is necessary to clear the infection. For prosthetic joint infections, surgical intervention is often required, which may include removal of the prosthesis.
If septic arthritis is not treated promptly and effectively, it can lead to severe complications. The infection can destroy the cartilage and bone within the joint, resulting in chronic pain, deformity, and loss of function. The infection can also spread to other parts of the body, causing life-threatening conditions like sepsis or infective endocarditis. In rare cases, septic arthritis can affect unusual joints such as the pubic symphysis, which is particularly dangerous and requires immediate attention.
Overall, septic arthritis is a dangerous condition due to its rapid progression and potential for permanent joint damage and systemic infection. Early recognition, prompt medical evaluation, and aggressive treatment are essential to reduce the risk of serious outcomes. People experiencing sudden joint pain, swelling, and fever should seek immediate medical care to rule out or treat septic arthritis.