Yes, Lyme disease can cause swelling in the feet, most commonly through a condition called Lyme arthritis. About one in four reported Lyme disease cases involve arthritis, and while the knee is the joint affected most often, the ankle and smaller joints in the foot can also swell. This typically happens months after the initial tick bite, during the late stage of the disease.
How Lyme Disease Leads to Foot Swelling
After a tick bite, the Lyme-causing bacteria can spread through the bloodstream and settle in joint tissue. Once there, the bacteria trigger an inflammatory response: the joint lining thickens, blood vessels in the area multiply, and immune cells flood the tissue. This process produces visible swelling, warmth, and pain in the affected joint.
The ankle is one of the large joints commonly targeted by Lyme arthritis. In earlier episodes especially, smaller joints and surrounding structures like tendons and bursae (the fluid-filled sacs that cushion joints) can also be involved. So swelling might show up in the ankle, the midfoot, or even the smaller toe joints, though these presentations are less common than knee involvement.
In roughly 60% of people who go untreated for Lyme disease, arthritis eventually develops. The swelling pattern is distinctive: it usually affects just one or two joints at a time (rather than many joints symmetrically, as in rheumatoid arthritis), and it can come and go in intermittent flares over months to years.
When Foot Swelling Appears in the Course of Lyme Disease
Lyme disease progresses through stages, and the type of joint symptoms you experience depends on timing.
In the early stage, within days to about a month after a tick bite, you might notice muscle or joint pain that migrates from place to place. At this point, there’s typically no redness or visible swelling accompanying the pain. It’s more of a diffuse achiness that shifts around.
True joint swelling with warmth, visible puffiness, and localized pain belongs to late disseminated Lyme disease, which develops months to years after the initial bite. This is the stage when the bacteria have had time to establish themselves in joint tissue and provoke a sustained inflammatory reaction. The swelling may be constant or episodic, flaring up for weeks or months, subsiding, and then returning.
Joint Swelling vs. Fluid Retention
It’s worth distinguishing between two types of foot swelling. Lyme arthritis causes joint-specific swelling, meaning the ankle or a particular joint in the foot becomes puffy, warm, and painful to move. This looks and feels different from generalized fluid retention (edema), where both feet and ankles swell evenly due to excess fluid pooling in the tissue.
Lyme disease can, in rare cases, affect the heart through a condition called Lyme carditis. When the heart muscle becomes inflamed, it may not pump as efficiently, which could theoretically lead to fluid buildup in the lower legs and feet. However, Lyme carditis is relatively uncommon and tends to appear in the early disseminated stage, days to months after the bite, rather than the late stage. Heart involvement typically shows up as abnormal heart rhythms and fatigue rather than peripheral swelling. If you’re experiencing puffy feet without obvious joint pain or warmth, other causes of edema are more likely.
How Lyme Foot Swelling Differs From Other Arthritis
If you’re noticing swelling in your foot or ankle and wondering whether Lyme disease could be the cause, the pattern of symptoms matters. Lyme arthritis tends to affect one or two large joints asymmetrically. You might have a swollen right ankle with no symptoms on the left side. Rheumatoid arthritis, by contrast, usually affects the same joints on both sides of the body and tends to favor the small joints of the hands and feet.
Geography is another important clue. Lyme arthritis should be considered when joint complaints occur in areas where Lyme disease is common, particularly the Northeast, Upper Midwest, and Pacific Coast of the United States. A history of spending time outdoors in tick-prone areas, a known tick bite, or a prior bull’s-eye rash strengthens the possibility. Blood tests for Lyme antibodies are the standard way to confirm or rule out the diagnosis.
What Treatment Looks Like
Lyme arthritis is treated with antibiotics, typically a four-week oral course. Most people respond well, though the swelling doesn’t always disappear overnight. Joint inflammation can take weeks to months to fully resolve after treatment, even when the antibiotics have successfully cleared the infection. This lingering inflammation doesn’t necessarily mean the treatment failed. The immune response in the joint can persist for a while after the bacteria are gone.
A small percentage of patients develop what’s called antibiotic-refractory Lyme arthritis, where joint swelling continues despite adequate antibiotic treatment. In these cases, the ongoing inflammation appears to be driven by the immune system itself rather than active infection, and treatment shifts toward managing the inflammatory response directly.
During recovery, keeping the affected foot elevated when possible and staying moderately active can help manage swelling and stiffness. The earlier Lyme disease is caught and treated, the less likely arthritis is to develop in the first place, which is why prompt attention to early symptoms like the expanding rash, fever, and migratory aches matters so much.