Knee pain: causes, symptoms and when to see a doctor
Knee pain can come from cartilage wear (osteoarthritis), a meniscus or ligament injury, tendinitis or fluid inside the joint. Where it hurts and when it appears help point to the cause.
Educational information prepared by Dr. Belinda Martínez, physician and surgeon. Last updated: October 3, 2026. It does not replace an assessment by a doctor.
Most common causes of knee pain
- Knee osteoarthritis (gonarthrosis): cartilage wear; it usually hurts when walking, climbing stairs or after sitting for a long time.
- Meniscus injury: pain along the joint line, sometimes with clicking or locking.
- Chondromalacia or patellofemoral syndrome: pain around or behind the kneecap.
- Tendinitis (patellar or pes anserine): localized pain that increases with effort.
- Joint effusion: swelling from fluid inside the knee.
- Ligament injury: a feeling of instability after a twist or blow.
- Arthritis: inflammation from gout, rheumatoid arthritis or other causes.
By where it hurts
| Area of pain | Possible causes |
|---|---|
| Front (around the kneecap) | Chondromalacia or patellofemoral syndrome, patellar tendinitis, patellofemoral osteoarthritis |
| Inner side | Medial meniscus injury, osteoarthritis, pes anserine tendinitis (area below the joint) |
| Outer side | Lateral meniscus injury, iliotibial band syndrome |
| Back | Baker's cyst, meniscus or ligament injury, and other causes that require assessment |
This table is only a guide: the cause is confirmed by the exam and, if needed, by imaging.
How it is diagnosed
The doctor asks how the pain started, what makes it worse and whether there was a blow; examines the knee (mobility, stability, tender points) and, depending on the findings, orders tests.
- X-ray: shows the bone and joint space; useful for assessing osteoarthritis.
- Ultrasound: helps with tendons, bursae and fluid.
- MRI: shows the meniscus, ligaments and cartilage.
- Lab tests or joint fluid analysis, if arthritis or infection is suspected.
Management options by cause
There is no single treatment for every knee. In general, management starts with conservative measures and steps up if there is no improvement:
- Relative rest and adapting activity, avoiding what triggers the pain.
- Weight control: every kilo lost reduces the load on the knee when walking.
- Strengthening the quadriceps and hip, guided by a physical therapist.
- Medications for pain or inflammation, only as prescribed by a doctor.
- Injections (for example corticosteroids or hyaluronic acid) in selected cases.
- Surgery (arthroscopy, meniscus or ligament repair, knee replacement) when there is a mechanical injury or advanced wear that does not respond to conservative management.
Biological therapies such as platelet-rich plasma are also being studied. Some studies suggest symptom relief in mild to moderate osteoarthritis, but protocols and the quality of the evidence vary, and they do not restore lost cartilage. Stem cells are still under investigation for this use. A doctor should assess whether any of these options applies to your case.
When to see a doctor
Seek medical care soon if you have any of these signs:
- You cannot bear weight on the leg after a blow or fall.
- The knee is red, hot and swollen, especially if you have a fever.
- Sudden swelling with no clear cause, or the knee locks and you cannot straighten it.
- Visible deformity or severe pain that does not ease with rest.
- Swelling, pain or redness in the calf (it may indicate a blood clot).
Frequently asked questions
Why does my knee hurt when I climb stairs?
Climbing stairs increases the load on the kneecap and cartilage. It is common in chondromalacia or patellofemoral syndrome and in osteoarthritis. If the pain persists, an assessment is worthwhile.
When is an MRI needed?
Not always. It is ordered when a meniscus or ligament injury is suspected, or when the X-ray and exam do not explain the pain. The doctor decides based on your case.
Can knee wear be cured?
Worn cartilage does not return to its original state, but many people control their symptoms well with exercise, weight control and other measures. It is a condition that is managed long term.
Can I exercise with knee pain?
In general yes; the right exercise helps. Choose low-impact activities and guided strengthening, and avoid what triggers the pain. Ask your doctor or physical therapist what is safe for you.
Book your free assessment
Dr. Belinda Martínez reviews your case at her office in Guadalajara. The assessment is free of charge and does not commit you to any treatment.
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This content is informational and educational; it is not a diagnosis or a treatment recommendation. If you have any symptoms, consult a health professional.