Knee osteoarthritis

Osteoarthritis affects the cartilage surfaces of the knee joint, and the bone, ligaments and lining around them. It typically causes pain that comes on with activity and stiffness that eases within about half an hour of getting going, and it is diagnosed clinically — from the history and the examination — rather than from a scan. Severity is judged by what the knee stops you doing, which corresponds only loosely to what an X-ray shows.

Symptoms

  • Pain brought on by activity — walking, stairs, standing — which eases with rest.
  • Stiffness first thing in the morning or after sitting, typically easing within about half an hour.
  • Swelling that comes and goes, and grinding or creaking on movement.
  • Difficulty with stairs, kneeling, squatting and getting out of a low chair.
How knee osteoarthritis develops

Osteoarthritis is a change in the whole joint rather than simple wear of the cartilage. The surface thins, the bone beneath it thickens, small bony spurs form at the edges, and the lining of the joint becomes inflamed at times. Age, previous injury, previous surgery, body weight, the alignment of the leg and work involving heavy loading all contribute, and a knee that has lost meniscal tissue or carries an old ligament injury is more likely to develop it. It does not progress at a steady rate: periods of more pain and periods of less are typical, and symptoms do not track the changes on an X-ray closely.

How it is assessed

Assessment begins with how the problem started and what the knee has done since, followed by an examination of both knees so the affected side can be compared with the other. Imaging is used where it would change what is done, rather than as a matter of routine.

In clinic

In a person over about 45 with activity-related knee pain, and either no morning stiffness or stiffness lasting no more than thirty minutes, osteoarthritis can be diagnosed without imaging. The examination assesses range of movement, alignment, swelling, muscle strength, gait and which activities are limited. It also looks for the features that would suggest something else — inflammatory arthritis, infection, or a mechanical block from a displaced meniscal tear.

Imaging

Imaging adds little to a typical presentation and is not needed to make the diagnosis. Standing X-rays are used where the picture is atypical, where another diagnosis is possible, or where surgery is being considered and the alignment and the pattern of involvement need to be known. MRI is not routine: degenerative findings are so common on scans of knees without symptoms that it can point away from the real problem rather than towards it.

Stage and severity

The changes are described by their extent and by how much they affect day-to-day activity.

Extent of the changes
On X-ray, the changes are graded by joint space narrowing, bony spurs and the density of the bone beneath the surface — most often on the Kellgren–Lawrence scale, from nought to four. The grade describes the appearance, not the symptoms.
Effect on daily activity
What the knee stops you doing: how far you can walk, stairs, sleep, work. This, rather than the grade on a film, is what treatment decisions are based on.
With other conditions
Whether one compartment is involved or the whole joint, a coexisting meniscal lesion, alignment that loads one side, or an inflammatory condition. These affect both what non-surgical treatment can achieve and which operation, if any, is appropriate.
Associated conditions

Degenerative meniscal lesions are found in most knees with osteoarthritis and are usually part of the same process rather than a separate problem to be treated separately. Alignment that carries load through one compartment accelerates change in that compartment, and is relevant if surgery is being considered. Osteoarthritis in the knee often accompanies pain elsewhere and conditions that limit activity generally, which is why the assessment covers overall function, weight and the other joints rather than the knee alone.

Treatment options

The two options below are set out side by side. Which applies depends on the findings, the structures involved and what you need to return to.

Non-surgical care

What it involves
Education about the condition, a structured exercise programme combining strengthening with aerobic activity, and weight management where it applies — these three are the core treatments. Topical anti-inflammatory gel is the usual first medication, with oral anti-inflammatories at the lowest effective dose for the shortest period if that is not enough. A corticosteroid injection may be used for a flare. Walking aids and braces are considered where there is instability, or where exercise alone has not been enough.
Typical course
Exercise is continued long-term rather than taken as a course. Pain often increases at first and then improves with consistency, and a weight loss of around ten per cent gives more benefit than five.
Considerations
Core treatment for everyone, including those who go on to surgery. Paracetamol and opioids are not routinely recommended, injections of hyaluronic acid are not recommended, and glucosamine and chondroitin are not supported by the evidence.
Follow-up
Reviewed as the programme continues, with medication reconsidered at each review.

Surgical treatment

What it involves
Knee replacement, either of the whole joint or of the affected compartment alone, and in selected younger patients an osteotomy to shift load away from the worn compartment. Arthroscopy is not a treatment for osteoarthritis.
Typical course
An inpatient stay of a few days, walking with support from the first day, and rehabilitation over several months, with improvement continuing for up to a year.
Considerations
Considered when symptoms are substantially affecting quality of life and non-surgical treatment has not worked or is unsuitable. Referral is based on clinical assessment rather than on a scoring system, and should not be withheld on the grounds of age, sex, smoking, body mass index or other conditions.
Follow-up
Reviewed after the operation and at intervals thereafter.

What recovery involves

Recovery depends on which treatment is used. The stages below apply to knee replacement, and the timings are typical rather than fixed — progress is judged on what the knee can do at each stage.

  1. In hospital and just after

    The first two weeks

    Walking with support, controlling swelling and pain, and regaining straightening and bending.

  2. Early rehabilitation

    Weeks 2 to 6

    Walking without aids, full straightening and bending past ninety degrees, and a return to light daily activities.

  3. Strength and function

    Weeks 6 to 12

    Strengthening, stairs and longer distances, and for many people a return to driving and to work.

  4. Continued improvement

    Months 3 to 12

    Return to low-impact activity such as walking, cycling and swimming, with pain and function continuing to improve over the first year.

Page information

Reviewed by
Dr Lai Kah Weng
Version
1.0
Review date
September 2026
Next review
September 2027

References

  1. National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management. NICE guideline NG226. London: NICE; 2022.
  2. Bannuru RR, Osani MC, Vaysbrot EE, et al. OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis. Osteoarthritis Cartilage. 2019;27(11):1578–1589.
  3. American Academy of Orthopaedic Surgeons. Management of Osteoarthritis of the Knee (Non-Arthroplasty): Evidence-Based Clinical Practice Guideline. 3rd ed. Rosemont, IL: AAOS; 2021.
  4. Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957;16(4):494–502.

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