knee anatomy illustration
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It's Complicated

Your knees have lots of moving parts, and you use them a lot, so lots of things can go wrong. Too much of one kind of motion, especially if you don't work up to it, can lead to "overuse" injuries. Simple wear and tear is a problem, especially as you age. Accidents can crack bones and tear tissue. With some conditions, your body attacks its own joints. Your doctor can help you sort out what's going on with your knee when it doesn't feel right.

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normal knee vs dislocation
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Dislocations and Fractures

If your knee hurts intensely after a bump, bang, or fall, you may have broken one of the bones that meet up there -- the thigh, shin, and kneecap -- or shifted one out of place. Go to the emergency room or see a doctor as soon as possible. Sometimes fractures happen more slowly, causing tiny cracks at the ends of the leg bones. This can happen when you've started using your knee more.  

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torn anterior cruciate ligament
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Torn Anterior Cruciate Ligament

You hear a pop and can't move after you suddenly change direction -- often while playing soccer, football, or basketball. You may have torn your ACL, which connects the femur and the tibia and prevents the tibia from moving too far forward. Your knee will hurt and swell and feel unstable.

You can tear or strain any of the tissues that hold your knee together: Ligaments connect bones to each other; tendons connect muscle to bone. Irritated tendons from using them too much? That's tendinitis.

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iliotibial band syndrome
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Iliotibial Band Syndrome

The "IT band," a ligament that runs along the outside of your thigh, can rub against the bone and get irritated and swollen. You're more likely to get this when you run or ride your bike for exercise. It might hurt more if you go downhill or sit for a while. You may feel better after you warm up, but if you don't rest the injury and give it a chance to heal, it could get worse.  

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senior man on sofa holding knee
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Osteoarthritis

It's tough to bend or stretch your leg. Your knee feels stiff and sore and may swell after you've been moving around. You've probably worn down the cartilage, the stuff that helps cushion the ends of your bones. Because that takes time, this kind of arthritis is more common in people 65 and older. If you're younger, you may get it because you've used your knee a lot after an injury, like a ligament tear. 

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inflammatory arthritis
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Inflammatory Arthritis

Besides pain and swelling, you may also feel tired, sick, or feverish. When you have an autoimmune disease, your immune system, which is meant to fight off germs, may attack your knees. For example, rheumatoid arthritis tends to affect hands and other joints in pairs on both sides of the body. Lupus goes after joints, muscles, and organs all over. Psoriatic arthritis often causes thick, discolored patches of skin, along with joint pain.

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maid on knees cleaning floor
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Bursitis

This makes your knee swollen, stiff, and warm or tender to the touch, usually because you've overworked it. The condition is also known as "housemaid's knee" or "clergyman's knee" because people with these jobs are kneeling so much. It happens when small, fluid-filled sacs called bursa that help cushion your knee joint get irritated and swollen. You may ache even when you're resting.

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female runner
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Runner's Knee

You'll feel this in the front of your knee, around the kneecap. Your knee may hurt after you sit with it bent for a while or when you try to kneel. It may pop or crack when you climb stairs. Typically, patellofemoral pain syndrome comes from overuse, misalignment between your hip and ankle, a weak thigh muscle, or the breakdown of cartilage behind your kneecap -- or a combination of these. It's common in women and young athletes.

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torn meniscus in knee
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Torn Meniscus

A sudden twist or pivot -- especially with your full weight on your knee -- can tear a meniscus, the rubbery cartilage that acts as a cushion between the bones of your thigh and shin. You have one on each side of your ACL. They may be more susceptible to tears because of arthritis or age. The pain can be hard to pinpoint and describe. Your knee may get stiff, swollen, and hard to move and extend. 

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bakers cyst behind knee
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Baker's Cyst (Popliteal Cyst)

This fluid-filled sac at the back of your knee may bulge out or get so tight that it's hard to fully bend or stretch your leg. It may be caused by another problem, like arthritis or a tear in your meniscus. The cyst itself usually doesn't hurt unless it bursts, which can make the back of your knee and calf swell and bruise.

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pseudogout recurrent arthritis
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Gout and Pseudogout

Both have similar symptoms: The pain and swelling are often intense and hit you fast. Your knee may be stiff, red, and hot. It happens when crystals gather in the joint. Gout is from a buildup of uric acid and often affects the big toe. Pseudogout is caused by calcium pyrophosphate.

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draining fluid from knee
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Infection

Another illness or a direct injury to the joint can cause septic arthritis. The pain will come on quickly, and you'll also be sick, cranky, and running a fever. Your doctor may use a needle to take some fluid from your knee to figure out which bacteria is causing it so they know how to treat it. Though it doesn't happen as much, viruses and parasites can infect your joints, too. 

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woman at desk with sore back
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Referred Pain

Problems somewhere else -- in your back, hip, or foot, for example -- can make your knee sore. Nerves can move pain from one area to another, or your brain may get confused about the source of pain signals. The feeling is real, but there may be nothing wrong with your knee itself.

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legs elevated with knee on ice
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What You Can Do

Take over-the-counter NSAID drugs like ibuprofen and naproxen to ease pain and swelling. RICE -- rest, ice, compression, and elevation -- can often help, too: Get off your feet. Raise your leg so it's higher than your heart. Put a cold pack in a thin cloth or towel on your knee for 10-20 minutes at a time, several times a day. Wrap an elastic bandage around your knee when you're up and about, snug but not tight.

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doctor examining womans knee
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When to See Your Doctor

Don't wait if your knee pain is sudden and intense. Pick up the phone if it won't go away or gets worse.

To make a diagnosis, your doctor might take X-rays or other images of your knee. Blood or knee fluid samples can help confirm or rule out certain conditions. Treatment may include medication, special exercises, braces, or in some cases surgery. Losing weight could help lessen pressure and strain on your knees.

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Sources | Medically Reviewed on 09/12/2019 Reviewed by Tyler Wheeler, MD on September 12, 2019

IMAGES PROVIDED BY:

1) Stocktrek Images / Science Source

2) (Left to right)  stockdevil / Thinkstock, Steven Needell / Science Source

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4) Peter Gardiner / Science Source

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6) Martin Rotker / Medical Images

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12) Hercules Robinson / Medical Images

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15) Pixel_away / Thinkstock

 

SOURCES:

Mayo Clinic: "Knee pain," "Torn meniscus," "Baker's cyst," "Gout," "Pseudogout," "Septic arthritis."

UpToDate: "Approach to the adult with knee pain likely of musculoskeletal origin," "Approach to the adult with unspecified knee pain," "Iliotibial band syndrome."

OrthoInfo: "Common Knee Injuries," "Patellofemoral Pain Syndrome," "What Are NSAIDs?" "Sprains, Strains and Other Soft-Tissue Injuries."

Arthritis Foundation: "What is Osteoarthritis?" "Benefits of Weight Loss."

National Institute of Arthritis and Musculoskeletal and Skin Diseases: "Arthritis," "Rheumatoid Arthritis," "Gout" "Handout on Health: Rheumatoid Arthritis."

CDC: "National Institute for Occupational Safety and Health: Preventing Knee Injuries and Disorders in Carpet Layers."

Annals of The Royal College of Surgeons of England: "Hip osteoarthritis: where is the pain?"

BMJ Case Reports: "Hip arthritis presenting as knee pain."

Medical News Today: "Knees ache? it could be your hips' fault."

Reviewed by Tyler Wheeler, MD on September 12, 2019

This tool does not provide medical advice. See additional information.

THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.