What Causes Knee Pain? Common Causes and How to Spot Osteoarthritis

Key Takeaways

Knee pain has many causes. The most common in adults is osteoarthritis, followed by ligament and meniscus injuries, tendinitis from overuse, and excess body weight.
Osteoarthritis tends to hurt gradually, worsening with use, with grinding sounds and brief morning stiffness — unlike an acute injury that usually hurts immediately after the event.
The best-evidenced care is weight loss and exercise. For chronic osteoarthritis pain that has not improved, genicular artery embolization (GAE) is a non-surgical option to consider before a knee replacement.

What can cause knee pain?

Knee pain rarely comes from a single cause. The knee bears heavy loads and is used constantly, so it is prone to wear, injury, and inflammation alike. Knowing what is causing the pain is an important first step, because each cause calls for a different approach.

In adults and older people, the most common cause is osteoarthritis — the slow wearing of the cartilage on the joint surface. In younger or active people, it more often comes from ligament or meniscus injuries, or tendinitis from repetitive overuse.

Osteoarthritis: worn cartilage, gradual pain, the most common cause in adults
Ligament or meniscus injury: often sudden pain after a twist or impact, with swelling or instability
Tendinitis and overuse: localized pain, often linked to activity or sport
Excess body weight: increases load on the joint and speeds up wear
Inflammatory or referred pain: e.g. rheumatoid arthritis, gout, or pain radiating from the hip or back

How can you tell if it is osteoarthritis?

Osteoarthritis has some telltale features that help separate it from other causes. Symptoms usually build up over months to years, worsen with prolonged walking, stairs, or use, and ease with rest. There is often a grinding sound in the joint and morning stiffness that clears within a few minutes.

This differs from an acute injury, which usually starts hurting right after a twist, impact, or fall, and may swell quickly, lock, or feel unstable. Immune-driven arthritis like rheumatoid tends to cause morning stiffness lasting over 30 minutes and affects several joints at once. Recognizing these patterns hints at the cause, but a firm diagnosis should come from a doctor.

Feature	Osteoarthritis	Acute injury
Onset of pain	Gradual, over months to years	Immediately after an event
Triggers	Long walks, stairs, use	Twisting, impact, a fall
Joint sounds	Chronic grinding	A pop or snap at the time of injury
Stiffness	Brief, a few minutes in the morning	From swelling after injury
Stability	Usually stable but painful on loading	May feel loose or lock up

Causes to watch out for and warning signs

Most knee pain is not dangerous, but some causes need prompt medical attention — such as a joint infection, which often brings fever, a very swollen, red, hot joint, and severe pain, or an acute gout flare, as well as rheumatoid arthritis, which can damage the joint if untreated.

Another commonly missed point is referred pain. Sometimes the real source is the hip or lower back, but the pain radiates to the knee. Overlooking this can lead to treating the wrong area. If knee pain comes with clear abnormal symptoms, see a doctor to find the true cause.

Signs of infection

A swollen, red, hot joint with severe pain and fever needs prompt medical care.

Inflammatory arthritis

Morning stiffness over 30 minutes, affecting several joints, warrants further testing.

Referred pain

The source may be the hip or back, radiating pain down to the knee.

How to manage it, and where GAE fits in

Whatever the cause, the best-evidenced foundation for osteoarthritis is weight loss and exercise to strengthen the muscles around the knee, together with appropriate pain medication. As for the increasingly popular PRP, stem cell, and growth factor injections, the evidence remains unclear and inconsistent, so they are not yet standard care.

For people with chronic osteoarthritis knee pain that has not improved with foundational care but who are not ready for — or do not yet need — a knee replacement, genicular artery embolization (GAE) is a needle-sized, non-surgical option that reduces inflammation and pain in suitable patients. An assessment by a team that can care for you across the full range, from the basics to specialized procedures, helps you find the plan that fits.

Core foundation: weight loss, exercise, and appropriate pain medication
PRP / stem cells / growth factors: evidence still unclear — not standard
GAE: a non-surgical option for chronic pain that has not improved, before surgery

Frequently Asked Questions

What kind of knee pain should worry me?

If pain is severe, the knee is swollen, red, and hot, you have a fever, you cannot bear weight, the knee is deformed, or it locks so you cannot move it, see a doctor promptly. Chronic pain that gradually worsens beyond 1–2 months should also be checked to find the cause.

How is osteoarthritis pain different from injury pain?

Osteoarthritis tends to hurt gradually, worsening with use and often with grinding sounds. An injury usually hurts right after a twist or impact, and may swell quickly, feel loose, or lock. If you are unsure, have a doctor examine it.

Is body weight really linked to knee pain?

Very much so. With every step, the knee bears several times your body weight, so excess weight increases the load and speeds up wear. Losing even a few kilograms genuinely reduces pain.

Does everyone with knee pain need an X-ray?

Not always. A doctor first considers your symptoms, age, and physical examination. If osteoarthritis or a clear injury is suspected, an X-ray or other imaging may be ordered to confirm and to plan the right treatment.

References

OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis (Osteoarthritis and Cartilage, 2019)
2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee (Arthritis & Rheumatology, 2020)

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