Knee Osteoarthritis: A Plain-Language Guide

If your knees ache on the stairs, feel stiff in the morning, or grumble when you stand up after sitting, you are far from alone — and knee osteoarthritis is one of the most common reasons. The word can sound final, but it really describes a gradual, very manageable process. Here is a plain-language guide to what it is, why it happens, and what genuinely helps.

What is knee osteoarthritis?

Osteoarthritis (OA) is the most common joint condition in the world — an estimated 528 million people were living with it in 2019, and the knee is the single most affected joint ¹. It is often called "wear and tear," but that is only half the story. OA is the whole joint slowly changing: the smooth cartilage that cushions the ends of the bones gradually thins, the bone underneath adapts, and the surrounding tissues can become inflamed and stiff ².

Cartilage has very little blood supply and limited ability to repair itself, so once it is worn it does not simply grow back. That sounds discouraging, but the encouraging part is that how the joint feels is only loosely linked to how it looks — and there is a great deal you can do to improve comfort and function.

What are the symptoms?

Knee OA usually comes on slowly, over months and years. The common signs are:

• Pain that is worse with activity and eases with rest (at least early on)
• Stiffness, especially first thing in the morning or after sitting a while
• A grinding or clicking sensation, or a feeling the knee might "give way"
• Trouble with stairs, squatting, or standing up from a low chair
• Reduced range of movement over time

Symptoms often fluctuate — good weeks and bad weeks are normal and don't necessarily mean the joint is rapidly worsening.

Why does it happen?

OA develops from a mix of factors that increase load or change how the joint works over time ²:

• Age — the most common single factor, as tissues change over decades
• Body weight — extra load multiplies the force through the knee with every step
• Previous injury — an old ligament tear or fracture can set it off years later
• Repetitive overload — certain jobs or activities that stress the joint
• Alignment and genetics — how your legs load and a family tendency both play a part

How is it diagnosed?

Diagnosis is mostly clinical — your story and a physical examination — sometimes supported by imaging. On an X-ray, doctors look for narrowing of the joint space, small bony growths (osteophytes), and a brightening of the bone beneath the cartilage. If you have ever seen the phrase "subchondral sclerosis" on a report, that is one of those imaging findings — and, as we explain in that article, it is read alongside your symptoms rather than on its own.

Importantly, the amount of change on a scan does not reliably predict how much pain you will have, which is why imaging is interpreted together with how you actually feel and move ³.

What helps? The foundations first

Care for knee OA is built from the ground up, and most of the foundation is things you can start now ²:

• Movement and exercise. This is the single most evidence-backed step. Strengthening the muscles around the knee, gentle low-impact activity (walking, cycling, swimming) and keeping the joint moving all reduce pain and improve function. Rest beyond a flare usually makes stiffness worse, not better.
• Weight management. Because load multiplies through the knee, even a modest reduction in body weight can meaningfully lower the force the joint carries.
• Physical therapy. Tailored strengthening and movement coaching helps you do the above safely and effectively.
• Symptom relief. Pain or anti-inflammatory medication, used as guided by a clinician, can make it easier to stay active — which is the real goal.

These foundations do most of the heavy lifting for most people, at every stage.

What about injections, regenerative options, and surgery?

When the basics aren't enough, there are further steps — considered individually, not as a default:

• Injections such as corticosteroids (for short-term flare control) may be used in some cases.
• Regenerative approaches like stem cell therapy are an area of active research for knee OA — promising in early trials, but not yet standard, proven care. We look at the honest evidence in stem cells for knee osteoarthritis.
• Surgery, including joint replacement, is highly effective for advanced, end-stage knees that significantly affect daily life — but it is the last step, not the first.

What we see at the clinic

The word people fixate on is "bone-on-bone," and they often arrive expecting the only answer to be surgery. In most people we see, that is not where the conversation starts. The honest truth is that the unglamorous foundations — getting stronger, moving more, managing load — change how knees feel more often than people expect, and they are worth doing properly before anything more involved. A good assessment is about matching the step to the stage, and being straight with you about what each option can and can't do.

Common questions

Does "bone-on-bone" mean I need surgery? Not automatically. It describes advanced cartilage loss on imaging, but the decision depends on your symptoms, function and goals — many people manage well without surgery.

Should I rest my knee or keep moving? Keep moving, within reason. Beyond settling a flare, gentle low-impact activity and strengthening generally help more than rest. Get tailored advice on how.

Does losing weight really make a difference? Yes — because force through the knee multiplies with body weight, even a modest reduction can lower the load the joint carries with every step.

Can the cartilage be repaired? Worn cartilage does not simply grow back, and no current routine treatment reliably regrows it. The realistic and worthwhile goal is better comfort, strength and function.

Key takeaway

Knee osteoarthritis is common, gradual, and far more manageable than the name suggests. How a scan looks matters less than how you feel and move — and the everyday foundations of movement, strength and weight management do the most good for the most people. If you want a plan matched to your knee, that starts with a proper assessment.