Understanding knee pain: osteoarthritis and kneecap pain

A friendly guide to the two most common causes of long-lasting knee pain: knee osteoarthritis and patellofemoral (kneecap) pain. What they are, how they're diagnosed, and why there's real hope.

6 min read · last reviewed October 1, 2026

Your knees do a lot of work. They carry you up stairs, down to the floor to play with grandchildren, and through thousands of steps a day. So when a knee starts to hurt, it can affect your whole life.

This guide explains the two most common causes of knee pain that lasts or keeps coming back: knee osteoarthritis and pain around the kneecap (patellofemoral pain). The good news for both: there is a lot you can do, and exercise is the treatment with the strongest evidence.

How your knee works

Your knee is where your thigh bone meets your shin bone. Your kneecap sits in a groove at the front of the thigh bone. The ends of these bones are covered with smooth, slippery cartilage that lets them glide. Two rubbery pads called menisci act as cushions. Strong ligaments hold the joint together, and big muscles, especially the thigh muscles (quadriceps) and hip muscles, move and support it.

Knee osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis. It affects millions of people, and the knee is one of the most common places to have it.

What happens in the joint? The cartilage gets thinner and rougher. The bone underneath changes, and small bony bumps can form at the edges. The lining of the joint can get irritated, causing swelling. The muscles around the knee often get weaker.

It's not just "wear and tear." Osteoarthritis is better thought of as the joint's ongoing repair process not keeping up. The joint is a living tissue that is always repairing itself, and many things affect it, including age, genes, past injuries, muscle strength and body weight. This matters, because it means the right kind of movement helps rather than harms.

Common symptoms:

• Pain when you are active, such as walking, climbing stairs or getting up from a chair
• Stiffness in the morning or after sitting, which usually eases within 30 minutes
• Swelling now and then
• A creaky or grinding feeling (this is common and usually not a concern)
• The knee feeling weak or less steady

Symptoms often come and go. Good weeks and bad weeks are normal. A "flare" doesn't mean your knee is getting worse.

It doesn't always get worse. Many people's symptoms stay about the same for years, and some improve, especially with exercise.

Something you can do today: Notice what makes your knee feel better and what makes it worse. Jot it down to share with your care team.

How is knee osteoarthritis diagnosed?

You often don't need an X-ray. UK guidelines say doctors can diagnose osteoarthritis without imaging in people who:

• are 45 or older, and
• have joint pain related to activity, and
• have no morning stiffness, or stiffness that lasts no longer than 30 minutes.

Your doctor will examine your knee and ask about your symptoms. An X-ray may help if your symptoms are unusual, or if you are being considered for surgery.

X-rays don't tell the whole story. Some people with big changes on X-ray have little pain. Others with small changes have a lot of pain. Your symptoms and what you can do matter more than the picture.

Pain around the kneecap (patellofemoral pain)

Patellofemoral pain is a dull ache at the front of the knee, around or behind the kneecap. It is very common in teenagers, young adults and active people, especially runners. It is more common in women.

It is often worse when you:

• Go up or down stairs or hills
• Squat, kneel or jump
• Sit for a long time with your knees bent (sometimes called "moviegoer's knee")

It usually happens when the load on the knee gets ahead of what the tissues are ready for, for example a quick jump in running, or weakness in the hip and thigh muscles. It is not a sign of damage to the kneecap.

What helps: An international consensus statement recommends exercise that strengthens both the hip and the knee muscles as the main treatment. Easing back on aggravating activities for a while, then building back up, also helps. Foot orthotics (shoe inserts) and kneecap taping may give some short-term relief for some people. A physiotherapist can guide you.

Most people improve with a few months of steady exercise, though it can take time and patience.

Other causes of knee pain

Other causes include injuries to the ligaments or menisci, tendon problems, gout and inflammatory arthritis. See a doctor if your knee swelled quickly after an injury, locks or gives way, or is hot, red and swollen. See the warning signs on our knee pain page.

The hopeful part

Whether you have osteoarthritis or kneecap pain, you are not stuck. Strengthening exercise, staying active, managing your weight if needed, and simple pain relief help most people move better and hurt less. Our next guide, Knee osteoarthritis: your treatment options, explains each option.

Something you can do this week: Try a simple exercise, such as sitting and straightening one knee slowly, 10 times on each leg, once a day.

Questions to ask your care team

• What do you think is causing my knee pain?
• Do I need an X-ray? Why or why not?
• What exercises are best for me, and how often should I do them?
• Can you refer me to a physiotherapist or a knee exercise programme?
• What should I do if my knee flares up?
• Which signs mean I should come back sooner?

This article is general information, not medical advice. Talk with your health care team about your own situation. In an emergency, call 9-1-1 or your local emergency number.

In an emergency, call 9-1-1 or your local emergency number.

General information, not medical advice. It does not replace your own care team. If you think you or someone else is having a medical emergency, call 9-1-1 or your local emergency number. If you are in crisis or thinking about suicide, call or text 9-8-8 (Canada and the US).

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