Knee osteoarthritis is commonly described in four stages, from Stage 1 (minor) to Stage 4 (severe), based on how much cartilage has worn away and how narrow the joint space has become on an X-ray. Early stages cause little or no pain, while advanced Stage 4 often means bone-on-bone contact, significant pain and stiffness, and is when joint replacement may be discussed. Knowing the stage helps guide treatment, which moves from lifestyle steps early to surgical options later.
| Stage | Joint changes | Typical symptoms | Common care |
|---|---|---|---|
| Stage 1: Minor | Minor wear, tiny bone spurs, joint space still normal | Little or no pain | Lifestyle steps, staying active, weight management |
| Stage 2: Mild | More bone spurs, cartilage still fairly healthy, joint space normal | Stiffness and aching after activity or long rest | Exercise, physical therapy, over-the-counter pain relief, braces |
| Stage 3: Moderate | Clear cartilage damage and joint space narrowing | Frequent pain with walking, bending, and kneeling; swelling | Physical therapy, prescription options, injections as advised |
| Stage 4: Severe | Cartilage largely worn away, bone-on-bone contact, greatly narrowed joint space | Significant pain and stiffness, even at rest for some | Advanced pain management; knee replacement may be discussed |
Understanding the Four Stages
Osteoarthritis develops slowly as the smooth cartilage that cushions the knee wears down. Doctors often grade it using X-ray findings on the Kellgren-Lawrence scale, which runs from grade 0 (a normal knee) through grades 1 to 4; this article covers grades 1 to 4. Symptoms do not always match the grade exactly, but they tend to increase as the joint space narrows.
Stage 1: Minor
There is very minor wear and perhaps a tiny bone spur, but the joint space is normal. Most people have little or no pain and may not know anything is happening.
Stage 2: Mild
X-rays show more bone spurs, but the cartilage is still mostly healthy and the joint space looks normal. You may notice stiffness or aching after activity, after sitting for a while, or in the morning.
Stage 3: Moderate
Cartilage has clearly worn in places and the joint space narrows. Pain becomes more frequent with walking, bending, squatting, and kneeling, and the knee may swell after activity.
Stage 4: Severe
Most of the cartilage is gone, the joint space is greatly reduced, and bones can rub together. Pain and stiffness are significant and can affect daily life. This is the stage where a doctor may talk with you about knee replacement if other treatments no longer help.
When to See a Doctor
See a doctor if knee pain, stiffness, or swelling lasts more than a few weeks, limits your activity, or does not improve with rest and over-the-counter measures. Early care can help you stay active and slow the impact of the disease.
Frequently Asked Questions
What are the 4 stages of knee osteoarthritis?
They range from Stage 1 (minor wear, little pain) through Stage 2 (mild) and Stage 3 (moderate cartilage loss and pain) to Stage 4 (severe, bone-on-bone). Doctors grade them using X-rays plus your symptoms.
What does bone-on-bone mean?
It describes Stage 4, when the cushioning cartilage has worn away and the bones of the joint can contact each other, which often causes significant pain and stiffness.
Does a higher stage always mean more pain?
Not always. Symptoms do not perfectly match the X-ray stage. Some people have more pain than their images suggest, and some have less. Your treatment is based on both your symptoms and your imaging.
What stage needs a knee replacement?
There is no single rule. Knee replacement is usually discussed at Stage 4, or when pain and loss of function are severe and other treatments no longer help. The decision is individual and made with your surgeon.
Can osteoarthritis be slowed down?
Staying active, strengthening the muscles around the knee, maintaining a healthy weight, and following your care plan can help manage symptoms and protect the joint. Ask your doctor about a plan for your stage.
Related Reading on Know Your Surgery
- Total Knee Replacement: Overview, Types, and What to Expect
- Total Knee Replacement: When to Consider Surgery
- Total Hip Replacement: Overview, Types, and What to Expect
- How Much Does Total Knee Replacement Cost in the US?
Sources
- American Academy of Orthopaedic Surgeons (AAOS), OrthoInfo. Osteoarthritis. https://www.orthoinfo.org/en/diseases–conditions/osteoarthritis/
- American College of Rheumatology (ACR). Osteoarthritis. https://rheumatology.org/patients/osteoarthritis
- Centers for Disease Control and Prevention (CDC). Osteoarthritis. https://www.cdc.gov/arthritis/osteoarthritis/index.html
- NIH MedlinePlus. Osteoarthritis. https://medlineplus.gov/osteoarthritis.html
Medical Disclaimer
This article is for general education and reflects US clinical grading. Your stage and treatment are set by your own doctor based on your symptoms and imaging. This article is not medical advice.
