When there are problems that affect joints, or the areas where bones meet together, you may experience pain along with other symptoms like swelling and stiffness.

The knee is the largest and strongest joint in your body. Here’s what to know about the potential causes of joint pain in the knee, as well as the symptoms and treatment options.

Common causes of knee joint pain may include the following:


Arthritis refers to joint pain, stiffness, and inflammation.

While there are more than 100 types of arthritis, osteoarthritis (OA) is the one that most often affects the knee. OA is also most likely in adults over 50 years of age and is known as a “wear-and-tear” type of arthritis, where joint damage occurs from knee cartilage breaking down.

Other types of arthritis that can affect the knee include post-traumatic arthritis, which develops years after an injury, as well as rheumatoid arthritis (RA), an autoimmune disease in which your immune system may attack joints in both knees.


Bursitis is a type of inflammation of a bursa, which is a small sac that cushions your bones, tendons, and muscles. It can cause pain, swelling, and redness along the infected joint.

Prepatellar bursitis is a subtype that affects the kneecap. It’s caused by chronic kneeling, falls, or direct injuries incurred from contact sports or in people who work on their knees, like carpenters or floor installers.

Unlike arthritis, bursitis tends to have a sudden and severe onset. You might also feel pain that extends beyond the affected joint.


Gout is a common type of inflammatory arthritis that most often starts in your lower limbs, particularly the big toe. It’s caused by a buildup of uric acid in the body, which may then lead to the development of crystals within the affected joints.

A gout flare-up may cause severe pain, swelling, and stiffness that may last 1 to 2 weeks at a time. This condition is also most common in middle-aged adults.

Chondromalacia of the patella

Chondromalacia is specific to the kneecaps and is caused by a breakdown of cartilage. It’s most common in athletes, such as runners, as well as people born female. In some cases, it may evolve into OA.


Tendinitis is a type of overuse injury that results in inflammation of the tendons, which connect between your muscles and bones. The knees are commonly affected areas, as well as the hips, elbows, and shoulders.

Joint infection

Also known as septic arthritis or infectious arthritis, a joint infection may develop if a bacterial, viral, or fungal infection spreads to your joints. It most commonly develops in the knee joints, though the ankles, hips, and wrists are also sometimes affected.

Along with a rapid onset of pain and swelling, you might also experience fever and chills.

Medical emergency

This is a serious condition that requires antibiotics and joint drainage. Go to the nearest emergency center if you experience:


Mostly affecting people born female over the age of 50, osteoporosis is an age-related bone disease that can lead to weakness and fractures. It may affect any part of the body, though the wrists, spine, and hips are more common.


Fibromyalgia is known for causing widespread pain and extreme fatigue. Aside from pain in your joints, you may also experience flu-like symptoms and brain fog. The exact cause is unknown, but fibromyalgia is most common in people ages 30 to 55, and may accompany autoimmune disease.


Injuries from falls and direct blows to the knee may also cause joint pain. The most common types of knee-related injuries include fractures, as well as sprains, dislocations, and ligament tears.

Other possible causes of knee joint pain include:

  • Overuse injuries: Also called repetitive injuries, these are considered common in the knees, particularly among athletes.
  • Infectious diseases: Influenza, hepatitis, and mumps may all cause joint and muscle pain.
  • Cancer: Osteosarcoma, a type of bone cancer, may cause pain, swelling, and fractures in the affected leg.
  • Lupus: This autoimmune condition may cause muscle and joint pain, along with swelling, fever, and rashes.
  • Rickets: This childhood bone disease causes bowed legs and weak muscle tone.
  • Sarcoidosis: Aside from joint pain, this inflammatory condition may also cause a rash, fever, and swollen lymph nodes.

Symptoms of knee joint pain may vary based on the underlying cause, but can include:

  • pain that gradually develops over time
  • pain that’s worse in the morning or after rest
  • pain that may radiate beyond the knee area
  • tenderness
  • redness
  • flare-ups after vigorous activities
  • weakness, swelling, and stiffness in the knee that may limit range of motion
  • “creaking” sounds in the knee

Get medical help right away if your knee:

  • suddenly gives out
  • is in severe pain
  • swells or has fluid buildup
  • cannot move
  • causes you to limp
  • makes a “popping” sound upon injury
  • becomes locked (unbendable) or unstable

Knee joint pain may be diagnosed with a combination of the following:

  • Physical examination: A doctor will examine your knee for signs of an injury, as well as swelling, tenderness, or redness.
  • Symptom history: You’ll be asked about the symptoms you’re experiencing, including when they started, their severity, and whether rest or certain activities make them worse.
  • Gait issues: A doctor may look at whether you’re having issues with walking.
  • Imaging tests: These primarily consist of x-rays to look for joint damage, but sometimes a doctor may also order a magnetic resonance imaging (MRI) or computed tomography (CT) scan to get a better look at bones and soft tissues in your knee.
  • Lab tests: Blood testing may be ordered to help rule out autoimmune diseases, gout, cancer, and other possible causes of knee joint pain.

A doctor might recommend:

  • RICE method: The rest, ice, compression, and elevation method can provide immediate treatment for injuries, tendinitis, and bursitis.
  • Wearing supports: These may include compression wraps and braces.
  • Assistive devices: Canes or other mobility devices can help take pressure off painful knee joints.
  • Exercise: Sometimes, light to moderate exercise can help alleviate knee joint pain when combined with periods of rest.

Medical treatment for knee joint pain may involve one or more of the following:

  • NSAIDs: Topical or oral nonsteroidal anti-inflammatory drugs may alleviate swelling and pain.
  • Acetaminophen: This type of pain medication may be recommended if you cannot take NSAIDs.
  • Corticosteroids: These oral medications or injections may treat severe swelling in the knee.
  • DMARDs: Disease-modifying anti-rheumatic drugs may be prescribed for conditions like RA.
  • Immunosuppressants: This may be beneficial for gout, lupus, or immune-mediated conditions.
  • Antibiotics: These may be prescribed if your knee joint pain is attributed to an infection.
  • Fluid drainage: This may be recommended for bursitis or joint infection.
  • Physical therapy: Here, you’ll learn exercises to help build strength and flexibility.
  • Surgery: This method is only reserved for severe cases when other treatments don’t work.

It’s important to see a doctor for a proper diagnosis of your knee joint pain so they can offer the correct treatment plan. Below are a few common questions you can ask at your appointment:

Why does my knee hurt when I bend it or straighten it?

Knee pain that occurs when you bend or straighten your leg could indicate a possible injury, arthritis, or tendinitis. See a medical professional for help.

What can cause knee joint aches without injury?

There are a number of conditions that can cause joint pain aside from an injury, such as arthritis or overuse. These may develop from joint swelling or damage.

How do I know if my knee pain is serious?

Any knee pain that doesn’t improve despite home remedies and rest ought to be examined by a medical professional. These could be signs of a serious underlying cause, such as arthritis, an infection, or another related condition.

There are several possible causes of knee joint pain, which makes early identification important in ruling out any potentially serious underlying conditions.

A doctor can help determine the underlying cause and help you come up with a treatment plan to alleviate pain and other possible symptoms.