We don’t often think of arthritis as being caused by an infectious agent, but rather consider it to be a byproduct of old age or something caused by an auto-immune disease. However, arthritis can occasionally be caused when a bacterial, viral, fungal or mycobacterial pathogen invades one or more joints, rapidly causing severe pain, stiffness, redness, warmth and swelling. The patient may also exhibit a fever and fatigue. Considered a medical emergency when it occurs, septic arthritis can completely destroy a joint in a matter of days and can spread throughout the body. Therefore, it is imperative that is be treated immediately. In this article, I will discuss the causes of Septic Arthritis and the treatments available.
The sterile fluid inside of our joints, called synovial fluid, plays a vital role in lubricating, nourishing and keeping our joints healthy. When this fluid is infected by a pathogen, its sterility is lost and it becomes an internal Petri dish in which bacteria or other agents quickly multiply. Pus usually forms as a result of the body sending white blood cells to fight the infection and the inflammation caused by this process can be extremely painful. Movement of the joint(s) can greatly exacerbate the pain and cause the patient to hold the joint as stiffly as possible.
How does a bad “bug” get inside of our joints in the first place? Human beings are prone to suffer minor injuries in the course of everyday life, like little scrapes, cuts and bruises. Occasionally, we will pick up an organism that doesn’t like to play nice and we get an infection. However, for that infection to reach the synovial membrane and fluid inside our joint, specific circumstances must occur, such as:
• An abscess or infection that allows blood-borne pathogens to enter the joint
• Joint surgery which allows an introduction of the pathogen into the joint space, such as joint replacement surgery or arthroscopy
• A soft-tissue or bone infection near the joint
• A penetrating injury to the joint
• An infection with gonorrhea
It is common for the bacteria to infect one joint, but there are microbes that will attack multiple joints. There are certain risk factors that can increase a person’s chance of contracting infectious arthritis, such as diabetes, alcoholism, sickle-cell anemia, immune-deficiency diseases, IV drug usage and rheumatic illnesses.
To make a diagnosis of septic arthritis, I listen to the patient describe their symptoms and ask about the speed at which the pain and inflammation developed. If Septic Arthritis is suspected, it is important to quickly determine if a pathogen is present in the synovial fluid and to then isolate the microorganism that is causing the infection. A sample of the synovial fluid of the affected joint will be withdrawn and sent for a culture and Gram stain. Other laboratory tests, such as testing levels of C-reactive protein and Sedimentation rates can be helpful. Early in the diagnostic process, X-rays will not be helpful, however ultrasound can reveal abnormally large amounts of joint fluid, called effusion, which causes swelling of the joint.
If the fluid is indeed infected with a microorganism, treatment will depend on the type of pathogen found. Because of the severity of this diagnosis, medication will likely be administered intravenously in the hospital or by a home health nurse. A specific antibiotic or a combination of antibiotics will be given, often for a period of six weeks.
Drainage of infected joint fluid is required for the treatment of septic arthritis. Fluid can be drawn off the affected joint with a hypodermic needle often (if not daily) and the joint will be injected or “washed out” with antibiotics and saline, to kill bacteria. More extensive joint cleaning can be done using arthroscopic surgical techniques and the infected synovial membrane can be removed as well. More often, it is necessary to surgically open the joint entirely to drain and clean it out thoroughly. Often, surgical drains will be left in the joint to allow it to drain while healing from infection, in a native (non-replaced) knee.
As my specialty in Orthopaedics involves joint revision/replacement surgery, I have a great deal of experience in dealing with patients who have joints that have become infected during their joint replacement surgeries. Treating those patients is a bit different, because the prosthetic joint surface will often acquire a film–like substance on its surface, which is resistant to antibiotics. I usually have to take those patients back into surgery and clean out their infected joint. Sometimes, I can debride and wash out the prosthesis and pack it with antibiotics, close the wound and continue with IV antibiotics. Sometimes, long-term treatment is necessary for chronic infection. Unfortunately, some people must have their joint prosthesis totally removed to allow for the infection to heal, at which point they can again have their joint prosthesis put into place. In rare cases, the joint infection will be so severe that the prosthesis can never be replaced or that amputation will be necessary.
Patients are followed very closely after Septic Arthritis and I look to make sure that they do not run a fever, that their pain and swelling diminishes, that their lab values return to normal and that they regain function of the joint. Long term, the prognosis of a patient depends on many factors, including how quickly they were treated, how aggressively they were treated, which microorganism caused the infection, and the general condition of their health.
While Septic Arthritis is not a condition anyone would wish to have, rapid diagnosis, immediate and comprehensive treatment and careful monitoring of the patient can help them to recover without lingering effects and permanent joint damage.
John D. Burrow, DO is a Joint Revision and Reconstruction Fellow who practices at Orthopaedic & Spine Center in Newport News, VA. To learn more about Dr. Burrow or OSC, go to www.osc-ortho.com or call us for an appointment at 757-596-1900.