Knee Osteoarthritis
What knee osteoarthritis is, how it is assessed and graded, what actually helps at each stage, and when a joint replacement becomes the sensible option.
Osteoarthritis is loss of the smooth cartilage surface of the joint, with changes in the bone underneath and inflammation of the lining. It is the most common reason people are referred to a knee surgeon.
It is also frequently over-treated at one end and under-treated at the other: patients are sold injections they do not need, and patients who would benefit enormously from a replacement wait years because they were told they were too young.
What it feels like
- Pain with weight bearing, worse on stairs and slopes
- Stiffness after sitting, easing after a few minutes of movement
- Swelling, particularly after activity
- Grinding or crunching
- Difficulty rising from a chair or squatting
- Over time, the leg becoming visibly bowed or knock-kneed
Pain at night and pain at rest are the features that most often tip a patient toward considering surgery.
How it is assessed
Weight-bearing X-rays are the mainstay. Loading the knee reveals how much joint space has actually been lost. Films taken lying down understate it, which is a common source of confusion between what a patient was told and what a surgeon sees.
Examination matters as much: alignment, range of movement, ligament stability, which compartment is tender, and whether the hip is contributing.
MRI is for soft tissue questions. It is often unnecessary for diagnosing or grading arthritis, and a degenerate meniscal tear reported on MRI in an arthritic knee is usually a finding rather than the cause of the pain.
What actually helps
Roughly in order of how well supported they are:
- Strengthening. Quadriceps and hip muscles, progressively loaded, under supervision at first. This is the intervention with the best return.
- Weight reduction, where relevant. The load through the knee in walking is a multiple of body weight, so the mechanical effect is significant.
- Activity modification. Cycling, swimming, walking on the flat. Reducing deep squatting and stairs where possible. Not resting.
- Simple analgesia, used sensibly and reviewed.
- Corticosteroid injection for a flare. Useful for short-term relief, not a long-term strategy.
- Bracing or insoles in selected patterns of wear.
- Joint replacement, when the joint is worn out and the symptoms warrant it.
Injection therapies
Cell-based and platelet injections are widely offered for knee osteoarthritis. Where they are considered, it is in a knee with cartilage left rather than an end-stage joint, and alongside the measures above rather than instead of them.1
Stem cell therapy and PRP covers what is involved and who it suits. The evidence review sets out the figures.
When to consider replacement
Broadly, when the joint surface is worn out on weight-bearing imaging, and the pain is limiting what you can do, disturbing sleep, or making you give up activities that matter. Non-surgical treatment should have had a genuine trial first.
If the wear is confined to one compartment, a partial replacement may be appropriate. The comparison covers how that choice is made.
What to bring to a consultation
- Recent weight-bearing X-rays, and the reports
- A list of what you have already tried, and for how long
- An honest account of what you have stopped doing
- What you want to be able to do again
Common questions
Does bone on bone mean I need a knee replacement?
Not automatically. Bone on bone describes what the X-ray shows, not how much your life is affected. The decision to replace a knee is driven by symptoms and function, not by the radiograph alone. Some people with severe X-ray changes cope well with strengthening and weight management. Some with moderate changes are genuinely disabled. The imaging informs the conversation, it does not decide it.
Will an X-ray or an MRI tell us more?
For osteoarthritis, a weight-bearing X-ray is usually the more useful test, because it shows how much joint space is lost when the knee is actually loaded. A non-weight-bearing film understates the wear. MRI is better for soft tissue problems such as meniscal or ligament injury, and is often not necessary to diagnose or grade arthritis.
What is the single most effective thing I can do?
For most people it is a combination of strengthening the quadriceps and hip muscles and reducing weight where relevant. Neither is glamorous, and both are better supported by evidence than anything injectable. The mechanical effect of weight reduction on the knee is substantial, and it is the most underused intervention in the field.
Should I rest the knee?
No. Prolonged rest weakens the muscles that protect the joint and makes an arthritic knee worse. What helps is modifying the activity rather than stopping: cycling, swimming and walking on flat ground rather than deep squatting, running on hard surfaces and stairs.
Do supplements help?
The evidence for glucosamine and chondroitin is weak and inconsistent. They are unlikely to cause harm and some patients feel they help, but they should not displace strengthening and weight management, and they will not change the structure of the joint.
References
Related reading
Total Knee Replacement
What a total knee replacement involves, who it suits, what recovery asks of you, and the risks and alternatives worth understanding before deciding.
Do Stem Cell Injections Work for Knee Arthritis?
What the evidence and Malaysian regulations actually say about stem cell and PRP injections for knee osteoarthritis, and how to read the claims you are shown.
Partial or Total Knee Replacement: How to Decide
How surgeons choose between a partial and a total knee replacement, what each involves, how long they last, and the questions to ask if only one was offered.