Whether you overdid it on the tennis courts or have been texting and typing way too much, there are many reasons why one or more of your joints might be achy. When the cause of your discomfort is that obvious, there’s usually no reason to panic (though you should still see a doctor if it doesn’t go away). But what if your joints hurt and you have no idea why? Or you also have other weird symptoms you can’t explain? 

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In rare instances, your joint pain might be a signal that something pretty serious is going on, such as a sexually transmitted disease or an autoimmune disorder. Here’s a look at some of the scary conditions that could be making you sore.

Infectious (septic) arthritis

If you get a cut or puncture wound and don’t clean it well, “a nearby joint can get infected with common bacteria like Staphylococcus aureus or Streptococcus,” says Orrin Troum, MD, a rheumatologist at Providence Saint John’s Health Center in Santa Monica, CA. You’ll notice intense swelling and pain in the area, and fever and chills could follow.  (Don’t ignore these 4 signs of a staph infection.)

Knees are the most commonly affected joint, but hips, ankles, and wrists are also likely targets. You might need IV antibiotics, and your doctor might need to drain fluid from the infected joint. Left untreated, septic arthritis can lead to full-body sepsis, which can be fatal.

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Sorry, Paleo devotees. Too much protein can be hard on your joints. “If you eat too much protein, your body produces a lot of uric acid and can’t excrete all of it from your body,” explains Luga Podesta, MD, director of sports medicine at St. Charles Orthopedics in New York. “This causes an intense inflammatory reaction.” It’s called gout, and it’s one of the most painful types of arthritis you can experience. Symptoms of gout like heat, swelling, redness, and hard-to-ignore pain commonly appear first in your big toe, then spread to other joints.

Protein overload isn’t the only risk factor. Drinking too much alcohol or sugary drinks, getting dehydrated, or taking certain types of medicines (like beta-blockers) can also bring on a bout of gout. Carrying too much weight puts you at risk as well.

Lyme disease

Every year, an estimated 30,000 people are bitten by a tick and come down with this disease. “The tick latches onto your skin to suck blood out of your body, but its head has an infection that gets into your bloodstream,” Podesta explains. Early symptoms include fatigue, fever, headache, and in many cases, a bull’s-eye rash. “Still, it can be difficult to diagnose if you’re not in an area endemic to ticks,” says Podesta. (Here’s what it’s like to live with Lyme disease.)

If you don’t figure out that you have Lyme disease so you can treat it, the bacteria can spread to your joints, especially your knees. You might also develop neck stiffness and sore hands and feet. Over time, your heart and nervous system may be affected as well.


This autoimmune disorder “can wreck all your joints if left untreated,” says Troum. People with lupus have an overactive immune system that can mistakenly target joints, as well as skin, blood, kidneys, and other organs. Along with swollen, painful joints, you may develop a butterfly-shaped rash across your cheeks, but symptoms are different for everyone. Hair loss, trouble breathing, memory problems, mouth sores, and dry eyes and mouth can also be signs of lupus.

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This sexually transmitted disease (STD) doesn’t just affect your genitals; it can also wreak havoc on your joints, as it causes a painful condition called gonococcal arthritis. It affects women more than men and, surprisingly, is most common among sexually active teen girls.

If you have it, you may develop one hot, red, swollen joint (though some people end up with several painful large joints), along with other STD symptoms, says Troum. Those might include a burning sensation when you urinate, as well as penis discharge or increased vaginal discharge.

Rheumatoid arthritis

We hear about arthritis all the time, so its inclusion on this list might not come as a surprise. But rheumatoid arthritis (RA) is different than the wear-and-tear kind (osteoarthritis) that commonly develops with age. 

RA is an autoimmune disorder, and it disproportionally targets women: Of the more than 1.3 million people who have it, 75% are female. “It’s worrisome to see in young patients,” says Troum, who says he’s seen new mothers with such bad inflammation in their hands that they struggle to care for their babies. 

Tender, swollen joints and feeling stiff in the morning are classic RA symptoms. You might also have fatigue, fever, or weight loss you can’t explain.

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Although not all these causes of joint pain can be cured, they can be treated. Some will require a course of antibiotics or other prescription meds. Others may improve on their own with time and rest. But any lingering pain in your joints should be reason enough to check in with your primary care doctor. He’ll likely refer you to a rheumatologist, a doctor who specializes in arthritis, to make sure you get the right diagnosis and treatment you (and your aching joints) need.