The knee is the largest and most stressed joint in the body. Achy knee pain is usually from long-term causes that involve stress, inflammation (like from arthritis), or an untreated injury to the knee area. It is important to treat injuries as soon as you can to prevent problems in the future.
9 most common cause(s)
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What it feels like
Dull, achy knee pain is often a sign of a chronic condition that causes damage over time. Knees are used so often—for walking, stepping, sitting, climbing, even standing—making them susceptible to various conditions that can cause dull or achy pain.
Acute conditions come on suddenly, but the symptoms are similar to a chronic condition. If your pain is constant and does not go away, you should see a doctor.
Symptoms
- Swelling
- Stiffness
- Redness or feels warm
- Not able to fully extend or flex the knee
- A sensation of instability or "giving out" of the knee
- Popping noises upon movement
- Unable to put weight on the knee, especially after strenuous activity
Causes
1. Patellofemoral pain syndrome
Patellofemoral pain syndrome (PFPS) has many names including runner's knee. It is common and often from overuse while training for sports, especially if you have already had a knee injury or misalignment in the knee joint. This wears away the cartilage beneath the kneecap (patella), leading to pain during exercise.
Females and young adults who are active in sports are more likely to have PFPS, but it can affect anyone.
Other symptoms include
- Dull pain at the front of the knee and around the kneecap when running, squatting, climbing stairs, or sitting with knees bent.
Treatment and urgency: You can first see your primary care doctor who will examine you and likely want to do X-rays, CT scan, or MRI.
Treatment most often includes resting the knee, OTC anti-inflammatory drug (NSAIDs) like ibuprofen (Advil, Motrin), low-impact exercise like swimming or bicycling, physical therapy to strengthen and stabilize the knee, and orthotics (shoe inserts) if there is a misaligned stride.
Surgery is only for severe cases. It is done arthroscopically (small incision with a camera) and you can go home that day.
2. Meniscal injury
The menisci are two pieces of cartilage that act like shock absorbers in the knee and are between the lower end of the thigh bone and the top of the shinbone. A torn meniscus is commonly referred to as "torn cartilage" in the knee.
The meniscus is often damaged during another injury to the knee, especially when there’s a forceful, twisting movement or a direct hit like a tackle. But older people can tear a meniscus while doing everyday activity if the cartilage has become thin and worn over time.
Other symptoms include
- Pain, stiffness, and swelling
- Knee catches, locks up, or gives way
Treatment and urgency: A primary care doctor can diagnose a meniscus tear. They will take your medical history, examine you, and do simple motion tests and imaging like an X-ray or MRI.
Your doctor may want to wait and see if the injury heals on its own. You can help it heal by resting and icing it, and taking OTC anti-inflammatory medication (NSAIDs) like ibuprofen (Advil, Motrin). In some cases, arthroscopic surgery followed by rehabilitation may be needed.
3. Prepatellar bursitis
Prepatellar bursitis is an inflammation of the bursa—small cushion-like structures—that are in the front of the kneecap. Infrapatellar bursitis is an inflammation of the bursa beneath the kneecap. In both cases, the knee can become swollen and hurt.
Prepatellar bursitis is most often caused by overuse. It can also be from osteoarthritis of the knee or a knee that turns outward.
Other symptoms include
- Pain, tenderness, and swelling of the kneecap
- Pain in one knee
- Sudden knee pain
- Knee pain that gets worse when going up stairs or standing up
Treatment and urgency: Prepatellar bursitis is a common condition that can usually be diagnosed by your primary care provider after doing a physical examination and an X-ray, CT scan, or MRI. In most cases, you can treat it yourself. Surgery is rarely needed.
You can treat prepatellar bursitis by resting and icing the knee, taking OTC anti-inflammatory medication (NSAIDs) like ibuprofen (Advil, Motrin) for pain and swelling, doing physical therapy, and sometimes getting corticosteroid injections into the injured bursa.
4. Knee arthritis
Knee arthritis is when there is inflammation and unusual wear and tear of one or both of the two joints in the knee.
There are different types of arthritis. Osteoarthritis is most common. It is from damage to the cartilage that over time causes bones in the knee to rub together. Rheumatoid arthritis is from an autoimmune condition that attacks the joint. Post-traumatic arthritis is from an injury and is similar to osteoarthritis.
Other symptoms include
- Pain in both knees, which is worse when moving the joint
- Knee stiffness, especially in the morning
- Knee instability
- Swollen knee
- Difficulty walking
- Pain when resting or trying to sleep
Treatment and urgency: Knee arthritis cannot be cured, but you can try to relieve pain and discomfort.
Your primary care provider will examine you and want to take X-rays. An anesthetic may be injected into the joint to help with pain. Usually, if that makes the pain go away, then it means you probably have arthritis.
Treatment includes physical therapy, taking OTC anti-inflammatory medication (NSAIDs) like ibuprofen (Advil, Motrin) for pain and inflammation, and corticosteroid injections to relieve knee pain. In some cases, surgery and knee joint replacement may be needed.
5. Jumper's knee (patellar tendonitis)
Jumper's knee is also called patellar tendonitis or patellar tendinopathy. It is an inflammation of the patellar tendon, which runs from the bottom of the kneecap to the top of the shinbone.
While anyone can get jumper’s knee, it is most often an overuse injury in athletes, especially those who do sports involving jumping. Strenuous physical activity without first warming up, or tight and inflexible thigh muscles, can put additional strain on the patellar tendon.
Other symptoms include
- Pain just below the kneecap
- Knee stiffness
- First only feeling pain when exercising, but over time pain interferes with everyday movement
- Pain is worse when knee is bent, like when going up stairs
Treatment and urgency: It is important to get treated. Jumper’s knee does not get better on its own and will get worse as you continue to move the knee.
Your primary care provider will examine you and want to do imaging like an ultrasound or X-ray.
Treatment includes resting the knee, pain relievers, physical therapy, sometimes corticosteroid injections, and surgery if needed.
6. Iliotibial (IT) band syndrome
Iliotibial band syndrome is also called ITBS or IT syndrome. The iliotibial band is a long, thick connective tissue. The band starts at the top of the hip bone, runs down the outside of the leg, and attaches to the side of the knee.
ITBS is an overuse syndrome. Athletes who are training a lot, especially runners and cyclists, are most likely to get it. It happens when the IT band constantly rubs against the outside of the knee joint, causing pain and inflammation.
Other symptoms include
- Pain in one knee
- Pain on the outside of the knee, especially while running or while sitting with the knee flexed
- Pain that gets worse when going down stairs
Treatment and urgency Your primary care provider will examine you and do some simple stretching tests to help find the location of the pain. An MRI is also sometimes needed.
Treatment may include resting and icing the knee, and taking OTC anti-inflammatory medication (NSAIDs) like ibuprofen (Advil, Motrin). You should also try stretching exercises for the iliotibial band, strengthening the upper leg muscles, and, if needed, changing your training routine. Sometimes, you’ll need corticosteroid injections.
7. Osgood-Schlatter disease
Osgood-Schlatter disease causes swelling and pain on the front of the knee below the knee cap. It usually occurs in children 9 to 14 years old. It is common in kids after a growth spurt and those who play sports with a lot of running or jumping.
It should go away over time as the bones mature.
Other symptoms include
- Knee pain that gets worse when running or jumping
- Knee pain that gets worse when squatting or kneeling
Treatment and urgency: You should check with your child’s pediatrician. Often, you can treat Osgood-Schlatter disease by resting and icing the knee, and taking OTC anti-inflammatory medication (NSAIDs) like ibuprofen (Advil, Motrin). Depending on the pain, your child may need to limit activity, including playing sports.
Questions your doctor may ask about dull, achy knee pain
- Is the knee pain affecting one or both knees?
- Do you often feel your knees buckling?
- Where is your knee pain?
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References
- Calmbach WL, Hutchens M. Evaluation of Patients Presenting with Knee Pain: Part I. History, Physical Examination, Radiographs, and Laboratory Tests. American Family Physicians. 2003;68(5):907-912. AAFP Link
- Blahd WH, Romito K, eds. Knee Problems and Injuries. University of Michigan: Michigan Medicine. Updated November 20, 2017. UofM Health Link
- Khaund R, Flynn SH. Iliotibial Band Syndrome: A Common Source of Knee Pain. American Family Physician. 2005;71(8):1545-1550. AAFP Link
- Medications for Treatment of Knee Pain and Arthritis. Arthritis Foundation. Arthritis Foundation Link
- Hurley M, Dickson K, Hallett R, et al. The Health Benefits of Exercise for People with Chronic Hip and Knee Pain From Osteoarthritis. Published April 17, 2018. Cochrane Link