The stages of knee osteoarthritis are a way of describing how much wear a knee joint shows on an X-ray, graded from 0 to 4. Grade 0 is a normal knee. Grade 1 shows doubtful changes. Grade 2 is mild and usually the first grade a radiologist will call definite. Grade 3 is moderate, with clear loss of the space between the bones. Grade 4 is severe, the stage most people mean when they say “bone on bone.” The grading system is called Kellgren-Lawrence, and its five grades are what people mean by the stages of knee osteoarthritis. It has been the standard since 1957.
Here is the part that matters more than the number: your grade describes your X-ray, not your life. It does not decide whether you need surgery, and it does not by itself predict how much your knee will hurt. It is one input among several. This guide walks through what each grade actually means, why grade and pain so often disagree, and which non-surgical options tend to fit where.
How common is knee osteoarthritis?
Common enough that most families have someone dealing with it. According to the U.S. Centers for Disease Control and Prevention, 12.0% of American adults aged 20 and over have osteoarthritis, which works out to roughly 33.2 million people, based on national survey data from 2017 through March 2020. Arthritis of all types is broader still: the CDC reported in 2023 that 21.2% of U.S. adults, about 53.2 million people, have doctor-diagnosed arthritis.
The knee is the joint that most often becomes symptomatic. Research from the Johnston County Osteoarthritis Project, published in Arthritis Care & Research, put the lifetime risk of developing symptomatic knee osteoarthritis at 44.7%. Close to half of us, in other words. That is context worth holding onto when a report comes back naming a grade. You are not an outlier.
What are the stages of knee osteoarthritis, grade by grade?
The Kellgren-Lawrence system was published by JH Kellgren and JS Lawrence in the Annals of the Rheumatic Diseases in 1957, and a 2016 review in Clinical Orthopaedics and Related Research remains the standard modern reference for it. A radiologist looks for four things on the film: the space between the bones, bone spurs at the joint margins, hardening of the bone just under the cartilage, and any change in the shape of the bone ends.
| Grade | Label | What the X-ray shows |
|---|---|---|
| 0 | None | No features of osteoarthritis |
| 1 | Doubtful | Doubtful joint space narrowing, possible small bone spur |
| 2 | Mild | Definite bone spurs, possible slight joint space narrowing |
| 3 | Moderate | Multiple moderate bone spurs, definite narrowing, some bone hardening, possible deformity of the bone ends |
| 4 | Severe | Large bone spurs, marked narrowing, severe bone hardening, definite deformity of the bone ends |
Grade 1 of the stages of knee osteoarthritis: doubtful
A grade 1 knee is one where the radiologist is not fully convinced anything is wrong. There may be a hint of narrowing and possibly a very small bone spur. Symptoms at this grade are usually mild and intermittent: some ache after a long day on your feet, a bit of stiffness first thing in the morning that loosens up quickly. Many people never mention it to anyone. This is also the grade where changes in activity, strength and body weight tend to do the most good, which is a reason not to wait. If your symptoms started young, our guide to early-onset arthritis signs and treatment covers what else is worth ruling out.
Grade 2 of the stages of knee osteoarthritis: mild
Grade 2 is the first grade at which osteoarthritis is called definite. Bone spurs are clearly present. The joint space may look slightly reduced, or it may still look normal. People at this grade often notice stiffness after sitting for a while, discomfort on stairs, and an ache that follows a longer walk rather than accompanying it. Cartilage loss has begun, but there is still cartilage doing its job. Most people at grade 2 do well with a structured plan and never need anything invasive.
Grade 3 of the stages of knee osteoarthritis: moderate
At grade 3 the narrowing is definite rather than possible, there are several moderate bone spurs, and the bone just beneath the cartilage has started to harden in response to carrying more load than it was designed to. This is where symptoms usually become difficult to work around. Pain shows up during activity rather than after it. Swelling comes and goes. Stairs, kneeling and getting out of a car all become deliberate. Grade 3 is also the grade at which people are most often told, prematurely in our view, that their only remaining option is a joint replacement.
Grade 4 of the stages of knee osteoarthritis: severe
Grade 4 shows large bone spurs, marked joint space narrowing, severe hardening of the underlying bone and visible change in the shape of the bone ends. Where the joint space has closed entirely, the two bones contact each other directly, which is the finding behind the phrase bone on bone knee pain. Pain is often present at rest and at night, and the knee may have visibly bowed. Grade 4 is the stage where surgical opinions are most appropriate. It is not automatically the end of non-surgical options, and a fair number of people at this grade choose to manage the knee rather than replace it.
Why the stages of knee osteoarthritis and your actual pain often disagree
If you take one thing from this article, take this. The X-ray grade and the amount of pain a person feels correlate far more loosely than most people expect. We regularly see grade 3 knees in people who walk several miles a week without much complaint, and grade 2 knees in people who cannot get through a shift. Both are normal, and neither person is misreading the stages of knee osteoarthritis.
The reason is that an X-ray shows bone. It does not show inflammation, joint fluid, how strong the muscles around the knee are, how the leg is aligned, what the meniscus is doing, or how much you are asking of the joint each day. Those factors drive symptoms at least as much as the grade does. This is exactly why a treatment plan built only from a grade tends to disappoint, and why we score how you are actually doing alongside how the knee looks.
How we work out where you sit in the stages of knee osteoarthritis
At our Riverdale clinic the assessment has four parts, and the imaging is only one of them.
A weight-bearing X-ray. Kellgren-Lawrence grading is designed to be read off a plain radiograph taken with you standing, because standing loads the joint and reveals narrowing that a lying-down film can hide. We take digital X-rays on site, and we use fluoroscopy, a live moving X-ray, when a treatment needs to be placed precisely inside the joint.
Diagnostic musculoskeletal ultrasound. Ultrasound shows what a plain film cannot: fluid, soft tissue and the structures around the joint. It is diagnostic imaging, not a therapy.
A hands-on examination. Range of motion, alignment, swelling, ligament stability, strength and how you walk into the room. Some of the most useful information never appears on an image.
A WOMAC score. This is the part that lets us tell whether a treatment is working rather than guessing. The Western Ontario and McMaster Universities Osteoarthritis Index, validated by Bellamy and colleagues in The Journal of Rheumatology in 1988, is a 24-item questionnaire in three sections: 5 pain items scored 0 to 20, 2 stiffness items scored 0 to 8, and 17 physical function items scored 0 to 68. A higher score means a worse knee. We record it at your first visit so there is a real baseline, then we score it again later and compare. If the numbers have not moved, the plan changes. Your place in the stages of knee osteoarthritis tells us what we are working with. Your WOMAC score tells us whether what we are doing is helping.
If you have already had imaging elsewhere, bring it. Our guide to when a knee MRI is actually needed explains when an X-ray is enough and when it is not.
Which non-surgical treatments fit which of the stages of knee osteoarthritis?
We are a non-surgical clinic. We do not perform surgery, and when a knee genuinely needs a surgical opinion we say so and refer. Within that scope, here is roughly how the options line up. Treat this as orientation rather than a prescription, because the right plan depends on your examination and your goals as much as where you sit in the stages of knee osteoarthritis.
Grades 1 and 2
The foundation at every grade, and often sufficient on its own here. The 2019 American College of Rheumatology and Arthritis Foundation guideline for the management of osteoarthritis strongly recommends exercise for knee osteoarthritis, and strongly recommends weight loss for patients who are overweight or obese. Both are unglamorous and both work. Your plan includes physical therapy, and we can add specific exercises for knee osteoarthritis you can keep doing at home. If a flare needs settling quickly, a corticosteroid injection is an option; the same ACR guideline strongly recommends intra-articular corticosteroid injection for knee osteoarthritis. Steroid relief is short-acting and how often it can be repeated is clinically limited, usually to three or four times per joint per year.
Grade 3
This is where combining treatments tends to earn its keep. Hyaluronic acid injections, often called gel injections, supplement the fluid that lubricates and cushions the joint; our page on gel injections for knee pain covers what a series involves. Unloading knee bracing shifts load off the worn compartment mechanically, and the ACR guideline strongly recommends tibiofemoral knee bracing. Our guide to the unloader knee brace explains how the fitting works. Platelet-rich plasma, which concentrates growth factors from your own blood, is available here and is worth a conversation; note that PRP is usually elective and not covered by insurance, while the covered components of the program generally are. To be clear about what we do not do: we use PRP and hyaluronic acid, not stem cells.
Grade 4
Options narrow but they do not vanish. Bracing, injections and load management still help a meaningful number of people at this grade, and the honest framing is symptom control and function rather than structural change. If the knee is holding a lot of fluid, joint aspiration can drain it and provide fairly immediate relief. Some patients use this combination to postpone a replacement; some manage well enough without one; some are better served by a surgeon, and we will tell you which group we think you are in. Our page on alternatives to knee replacement goes through this decision in more depth.
All of it sits inside our Targeted Restoration Protocol, which is simply the structure we use to combine diagnostics, injections, bracing and therapy into one plan instead of trying things one at a time. In our own knee osteoarthritis program, around 90% of patients experience a 50% or greater improvement.
Other systems for staging knee osteoarthritis you might hear named
Kellgren-Lawrence is the one you will see most, but it is not the only system, and a second opinion may use different language for the same knee.
Outerbridge grades cartilage directly rather than bone, on a scale from softening through to exposed bone underneath. It was originally described by RE Outerbridge in 1961 for kneecap cartilage and is now applied to knee cartilage more broadly. Because it describes cartilage, it is used with MRI or arthroscopy rather than plain X-ray.
Ahlback grades weight-bearing radiographs on a five-point scale weighted toward bone loss, and it is used mainly in surgical planning. Reliability studies have found considerable disagreement between observers using it, which is part of why Kellgren-Lawrence remained the standard.
If two reports on the same knee use different numbers, that is usually the systems disagreeing rather than the knee changing. Kellgren-Lawrence remains the reference for the stages of knee osteoarthritis.
Do the stages of knee osteoarthritis always progress?
Not at a fixed rate, and not for everyone. Some knees stay at the same grade for a decade. Others change faster, particularly where there is a previous injury, a meniscus problem, significant extra body weight or alignment that concentrates load on one compartment. We do not think it is honest to give you a timeline, because the published research does not support a single reliable figure for how quickly a given knee advances, and a grade is a snapshot rather than a schedule.
What is reasonably well supported is that the modifiable factors are genuinely modifiable. Strength, body weight and how load is distributed across the joint are all things you can change, and all three influence both symptoms today and how the joint fares over time. That is the practical argument for acting early in the stages of knee osteoarthritis rather than waiting until grade 4 forces the issue.
Frequently asked questions
What are the 4 stages of knee osteoarthritis?
The four stages of knee osteoarthritis come from the Kellgren-Lawrence system, which grades what shows up on a weight-bearing X-ray. Grade 1 is doubtful narrowing with possible small bone spurs. Grade 2 is definite bone spurs with possible slight narrowing. Grade 3 adds multiple moderate bone spurs, definite narrowing and some hardening of the bone underneath. Grade 4 shows large bone spurs, marked narrowing, severe hardening and visible deformity of the bone ends. A grade 0 knee shows no arthritis changes at all.
Can the stages of knee osteoarthritis be reversed?
No. Cartilage that has already worn away does not grow back, and no injection, brace or exercise program restores a knee to a lower X-ray grade. What treatment can do is reduce pain, improve how far and how comfortably you move, and take load off the damaged part of the joint. Many people with a grade 3 knee function well for years. The goal is a knee you can live on, not a different X-ray.
Does a higher stage always mean more pain?
It does not. This is one of the most consistently surprising findings in knee osteoarthritis. Plenty of people with grade 3 changes walk comfortably, and plenty of people with grade 2 changes hurt every day. Pain depends on inflammation, swelling, muscle strength, body weight, alignment and how much you ask of the knee. That is why we score your symptoms separately from your imaging, rather than reading the stages of knee osteoarthritis as a pain scale.
Do I need an MRI to find out my stage?
Usually not. The Kellgren-Lawrence grading that defines the stages of knee osteoarthritis is read off a plain weight-bearing X-ray, which is faster, cheaper and the appropriate first study for suspected osteoarthritis. MRI becomes useful when the picture does not fit, for example when we suspect a meniscus tear or a soft-tissue problem alongside the arthritis.
At what stage should I see someone about my knee?
Sooner than most people do. If knee pain has lasted more than a few weeks, wakes you at night, makes stairs difficult or has changed how you walk, that is worth evaluating regardless of grade. Early grades usually give you more options, and knowing where you stand in the stages of knee osteoarthritis removes a lot of the guesswork. You can reach our Riverdale clinic at (470) 895-0610.
Get a straight answer about your knee
Knowing where you sit in the stages of knee osteoarthritis is useful mainly because it lets you stop guessing and start choosing. If you are somewhere between “it is probably nothing” and “I have been told I need a replacement,” an evaluation will tell you which of those is closer to true. We will grade the knee, score your symptoms against the stages of knee osteoarthritis, explain what we see and tell you plainly whether we can help.
Regenerative Joint Clinics is at 483 Upper Riverdale Road SW, Suite F, Riverdale, GA 30274. Call (470) 895-0610, email contact@regenerativejointclinics.com, or request a consultation. You can also read more about our approach to knee pain treatment in Riverdale, GA.
This article is for general education and is not medical advice. Talk with a qualified healthcare provider about your own knee before starting or changing any treatment. Individual results vary.
Featured image: “Osteoarthritis on X-ray” by James Heilman, MD, licensed CC BY-SA 4.0 via Wikimedia Commons.
