Lyme arthritis is a complication of Lyme disease, an infection transmitted by ticks. This condition primarily targets the joints, causing inflammation and discomfort. It is a manifestation of the later stages of Lyme disease, which can affect various organ systems.
How It Develops
Lyme arthritis begins with an infection by the bacterium Borrelia burgdorferi, though other Borrelia species can also cause similar disease in different regions. These bacteria are transmitted to humans through the bite of infected blacklegged ticks, specifically Ixodes scapularis in the eastern and midwestern United States and Ixodes pacificus in the western United States. Ticks acquire the bacteria by feeding on infected animals like mice or deer.
When an infected tick bites a human, Borrelia burgdorferi bacteria are transferred through the tick’s saliva into the bloodstream. The risk of transmission increases with the duration of the tick’s attachment, often occurring after 24 to 48 hours of feeding. Once in the body, the bacteria can spread to various tissues, including the joints.
Lyme arthritis develops weeks to months after the initial tick bite and infection. The bacteria entering the joint tissue trigger an inflammatory response, leading to the characteristic symptoms of arthritis. While joint aches can occur earlier, the pronounced inflammation of Lyme arthritis appears later.
Identifying the Signs
The primary symptom of Lyme arthritis is noticeable swelling in one or a few joints, most commonly affecting the knee. Other large joints such as the ankle, hip, shoulder, elbow, and wrist can also be involved, often in an asymmetrical pattern. The affected joint may also feel warm to the touch and exhibit redness around the area.
Joint pain is a common feature, although the level of pain may not always correlate with the degree of swelling. This joint inflammation can be episodic, with periods of swelling and pain followed by symptom-free intervals. These episodes can last for several weeks to months.
It is important to distinguish these joint symptoms from the initial signs of Lyme disease, such as the characteristic bull’s-eye rash (erythema migrans) or flu-like symptoms. Lyme arthritis manifests in the later stages of the infection, often after earlier symptoms have resolved or gone unnoticed. If left untreated, the persistent inflammation can lead to permanent joint damage.
Diagnosis and Treatment
Diagnosing Lyme arthritis involves evaluating a patient’s symptoms, considering their potential exposure to ticks in endemic areas, and conducting specific laboratory tests. Blood tests are the mainstay for confirming the diagnosis, specifically a two-tiered testing approach recommended by the Centers for Disease Control and Prevention (CDC). The first step is an enzyme-linked immunosorbent assay (ELISA) to screen for antibodies to Borrelia burgdorferi. If the ELISA result is positive or inconclusive, a Western blot test is then performed to confirm the presence of specific antibodies. All patients with Lyme arthritis have positive blood tests for Lyme antibodies.
In some cases, joint fluid analysis may be performed as an additional diagnostic tool. This involves aspirating fluid from the swollen joint and examining it. The white blood cell count in the joint fluid is often elevated, indicating inflammation, but this can also be seen in other types of arthritis, making serologic testing a more definitive approach.
The primary treatment for Lyme arthritis involves antibiotic therapy aimed at eliminating the bacterial infection. Oral antibiotics, such as doxycycline or amoxicillin, are commonly prescribed for a course of approximately 28 days. For patients who experience persistent joint inflammation or a lack of improvement after an initial course of oral antibiotics, a second course of oral antibiotics or intravenous antibiotics like ceftriaxone may be considered. Most patients respond well to antibiotic treatment, with resolution of symptoms occurring within one to three months. In a small percentage of patients, joint swelling and pain may persist even after antibiotic treatment, requiring additional anti-inflammatory therapies or referral to a rheumatologist.
Reducing Your Risk
Preventing tick bites is the most effective way to avoid Lyme disease and its complications, including Lyme arthritis. When spending time outdoors, particularly in wooded, grassy, or bushy areas where ticks thrive, it is advisable to wear protective clothing. This includes long-sleeved shirts, long pants tucked into socks, and closed-toe shoes to create a physical barrier against ticks. Choosing light-colored clothing can also help in spotting ticks more easily.
Applying EPA-registered insect repellents to exposed skin and clothing provides an additional layer of protection. Repellents containing ingredients such as DEET or picaridin are considered effective in deterring ticks. Always follow the product instructions for safe and effective use.
After returning indoors from outdoor activities, perform thorough tick checks on yourself, children, and pets. Pay close attention to areas such as:
- The back of the knees
- Groin
- Armpits
- In and behind the ears
- The belly button
- The scalp
Showering or bathing within a couple of hours of coming indoors can help wash away any unattached ticks. If a tick is found, remove it promptly and carefully using fine-tipped tweezers, grasping the tick as close to the skin as possible and pulling steadily upward without twisting or crushing it. The sooner a tick is removed, the less likely it is to transmit bacteria.