If You Feel This in Your Knee, Get Your Blood Checked, Says CDC

You have only a 30-day window for best treatment results.

As temperatures rise, you may find yourself spending more hours of the day outside. But just as the spring flowers begin to bloom, a seasonal threat also returns: ticks. Often beginning in the month of March, tick-borne illnesses such as Lyme disease find their way to new hosts at record rates, wreaking havoc on the body if left untreated. In fact, a Lyme infection can cause a range of confounding symptoms beyond the tell-tale bullseye rash. Experts say that recognizing one symptom in particular, which you may notice in your knee, could save you years of misery due to chronic Lyme. Read on to find out which symptom means it's time to have your blood checked for Lyme disease, and how you can protect your family from a Lyme infection this spring.

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If you experience recurring pain or swelling in the knee joint, get your blood checked.

Shot of a mature doctor examining his patient who is concerned about his knee

According to the Centers for Disease Control and Prevention (CDC), there are two main stages of Lyme disease. The first occurs during the initial 30 days after infection, and the second can begin any time after that. If you have not treated your Lyme disease infection within those first 30 days, your symptoms are more likely to escalate and spread, causing severe headaches, stiffness, intermittent pain, inflammation, dizziness, shortness of breath, swelling in the lymph nodes, and more.

In particular, the CDC warns that one symptom is considered common when it comes to chronic Lyme: "arthritis with severe joint pain and swelling, particularly the knees and other large joints." If you experience this with no known explanation, it's important to consult your doctor and request a blood test to screen for Lyme disease—especially if you believe you may have been exposed to a tick bite.

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Joint arthritis can cause permanent damage if Lyme is left untreated.


Lyme arthritis occurs when a Lyme infection causes inflammation in the joint tissue. "The main feature of Lyme arthritis is obvious swelling of one or a few joints. While the knees are affected most often, other large joints such as the shoulder, ankle, elbow, jaw, wrist, and hip can also be involved," explains the CDC. "People who do not receive prompt treatment for Lyme arthritis are at risk of developing permanent joint damage."

By looking out for the signs of Lyme arthritis, you may be able to treat your condition before this occurs. In addition to stiffness, "the joint may feel warm to the touch or cause pain during movement. Joint swelling can come and go or move between joints, and it may be difficult to detect in the shoulder, hip, or jaw. Lyme arthritis typically develops within one to a few months after infection," the CDC explains.

Look out for these early signs of Lyme disease.

Woman with flu in bed, she use thermometer to measure temperature

If you spot Lyme disease shortly after a tick bite and receive prompt antibiotic treatment, you should be able to make a full recovery. The CDC says that within the first 30 days, you may experience a more mild headache, fever, chills, muscle aches, joint aches, or swollen lymph nodes.

Importantly, you may also notice the tell-tale "Lyme rash," known among medical professionals as Erythema migrans (EM). This is most typically presents as a red "bullseye" at the site of the tick bite, which expands across the skin in the days following infection. An EM rash occurs in between 70 and 80 percent of Lyme disease cases, and develops in an average of seven days after an infected tick bite.

However, it is important to note that not everyone experiences a rash after contracting Lyme, so the absence of a rash does not mean you're in the clear if you have other symptoms.

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Be sure to practice Lyme disease safety.

hikers with bear spray

If you live in an area with ticks—especially in a heavily affected area, such as the Northeastern U.S.—it's important to make Lyme safety a priority. The CDC recommends avoiding walking through tall grass, bushes or other vegetation, opting instead to walk on trails when possible.

Additionally, you can protect yourself by using certain repellants, which can be applied to your shoes, clothes, camping gear, or skin, depending on the ingredients. "Use Environmental Protection Agency (EPA)-registered insect repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone. EPA's helpful search tool can help you find the product that best suits your needs," the CDC writes.

Finally, you should make it a habit to perform regular tick checks any time you come inside after spending time in nature. The CDC warns that ticks tend to hide in protected areas of the body, so it's important to check thoroughly, using a mirror if need be. In particular, take care to check under the arms, in and around the ears, inside the belly button, behind the knees, on the scalp, between the legs, and around the waist, their experts advise.

Speak with your doctor if you believe you may have been exposed to a tick bite, or if you're experiencing any symptoms of Lyme disease.

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Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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