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Health condition · Clinically reviewed

Knee joint osteoarthritis, from strengthening and injections to modern knee replacement.

The most common cause of knee arthritis in the UK - a stepped, NICE-based plan works for most, and modern surgery works when it doesn't.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a UK-registered specialist musculoskeletal clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE NG226, BASK, BOA and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK orthopaedic practice including unicompartmental knee replacement, robotic-assisted arthroplasty and unloader bracing.

Key facts

Knee joint osteoarthritis at a glance.

The essentials, in plain English - what it is, how common it is, and how it is treated in the UK today.

  • What it is

    A degenerative joint condition of the knee with progressive cartilage loss, subchondral sclerosis, osteophytes and low-grade synovitis.

  • How common

    The most common form of knee arthritis in the UK - present in more than 30% of adults over 65 and rising with obesity and longer life.

  • Compartments

    Medial (most common, varus), lateral (valgus), patellofemoral and tricompartmental - the pattern shapes treatment choice.

  • First-line therapy

    Weight loss and structured exercise with specialist musculoskeletal physiotherapy - the foundation of every NICE-based plan.

  • Joint injections

    Intra-articular steroid, and in selected cases hyaluronic acid or PRP, can bridge symptoms while more definitive options are planned.

  • Surgical options

    From joint-preserving high tibial osteotomy to unicompartmental or total knee replacement, including robotic-assisted arthroplasty.

Why this guide matters

A stepped plan, from strengthening to surgery.

Knee joint osteoarthritis is common, progressive and eminently manageable when the plan matches the person and the compartment.

  • Physiotherapy and weight are the foundation

    Specialist musculoskeletal physiotherapy and a 10% weight reduction do more, for more people, than any pill.

  • Injections buy time, not miracles

    Intra-articular steroid injections settle flares; hyaluronic acid and PRP are considered selectively in specialist clinics.

  • Modern surgery is targeted

    From high tibial osteotomy in younger patients to unicompartmental and robotic total knee replacement - the operation is matched to the compartment.

How the diagnosis is made

From first ache to a clear plan.

The steps a UK GP, specialist musculoskeletal team or orthopaedic surgeon will normally follow - so you know what to expect and why.

  1. 01

    Assessing

    History and red flags

    Insidious activity-related pain, short morning stiffness under 30 minutes, functional decline - and a check for anything that isn't osteoarthritis.

  2. 02

    Assessing

    Focused knee examination

    Joint-line tenderness, effusion, range of movement, crepitus, ligament stability, gait and varus or valgus alignment - a specialist musculoskeletal review.

  3. 03

    Assessing

    Impact and function

    Oxford Knee Score and simple functional tests put a number on stairs, walking distance, sleep disturbance and quality of life.

  4. 04

    Confirming

    Weight-bearing X-ray

    Standing plain films graded with the Kellgren-Lawrence system show joint space, sclerosis, osteophytes and alignment - ordered by a specialist musculoskeletal team.

  5. 05

    Confirming

    MRI when indicated

    Selective, not routine - useful for suspected meniscal or ligament injury, avascular necrosis or when the picture doesn't fit. Arranged via specialist review.

  6. 06

    Planning

    Compartment mapping

    Deciding whether disease is medial, lateral, patellofemoral or tricompartmental - the single most important step before considering surgery.

  7. 07

    Planning

    Orthopaedic MDT

    A specialist orthopaedic multidisciplinary team weighs age, activity, compartment pattern and alignment to choose osteotomy, unicompartmental or total knee replacement.

Typical pathway: a specialist musculoskeletal review and a weight-bearing X-ray usually settle the diagnosis in a single visit.

Symptoms

What knee osteoarthritis actually feels like.

The classic mix of activity-related pain, short morning stiffness and gradual functional decline - and the features that mean it is time to escalate.

  • Insidious knee pain

    A gradual, activity-related ache - worse on stairs, hills and after prolonged walking or standing.

  • Short morning stiffness

    Typically under 30 minutes - unlike inflammatory arthritis, it eases quickly with gentle movement.

  • Crepitus and grinding

    A palpable or audible grating on bending the knee - reflects cartilage wear and irregular joint surfaces.

  • Effusion and swelling

    Recurrent low-grade swelling after activity or a flare - responds to relative rest and simple analgesia.

  • Reduced range of movement

    Loss of full flexion and, later, a fixed flexion deformity - limits kneeling, squatting and stairs.

  • Varus or valgus deformity

    A bowing (varus) or knock-kneed (valgus) alignment develops as one compartment wears more than the other.

  • Antalgic gait

    A short-step limp on the painful side - a specialist musculoskeletal team can pick this up quickly.

  • Red flag - locking or giving way

    True mechanical locking suggests a meniscal tear or loose body - see our knee cartilage injury guide and seek specialist review.

Treatment

How knee osteoarthritis is treated in the UK.

Weight, exercise and specialist musculoskeletal physiotherapy first; NICE-guided medication and injections next; and, when needed, targeted knee surgery.

  • Weight loss and dietetics

    A 10% reduction in body weight makes a clinically significant difference to symptoms. Specialist dietetics helps make it stick.

  • Specialist musculoskeletal physio

    Quadriceps strengthening, core work and gait retraining - see our spinal physiotherapy guide for the wider musculoskeletal approach.

  • Analgesia and topical NSAIDs

    Topical NSAIDs are first-line per NICE. Paracetamol and short-course oral NSAIDs sit alongside, with cover for stomach and kidneys.

  • Intra-articular steroid injection

    A specialist musculoskeletal steroid injection can settle a flare and buy time - see our steroid injection guide for what to expect.

  • Hyaluronic acid, PRP and orthobiologics

    Selective options considered in specialist clinics for suitable patients - evidence is evolving and use is individualised.

  • Unloader bracing

    A custom brace offloads the worn compartment in varus or valgus disease - a useful step before or instead of surgery.

  • High tibial osteotomy

    A joint-preserving realignment for younger patients with medial unicompartmental disease and varus alignment - see our high tibial osteotomy guide.

  • Unicompartmental knee replacement

    Resurfacing only the worn compartment - faster recovery than a total knee. See our unicompartmental knee replacement guide.

  • Patellofemoral replacement

    Targets isolated kneecap arthritis - see our patellofemoral arthroplasty guide for the indications and rehabilitation.

  • Total knee replacement

    The definitive option for tricompartmental or advanced disease - open, minimally invasive or robotic (including Mako). See our knee replacement surgery guide.

  • Distal femoral osteotomy

    Realignment for lateral compartment osteoarthritis with valgus deformity - a specialist commissioned option in younger patients.

  • Orthopaedic MDT and follow-up

    Long-term care shared between an orthopaedic surgeon, physiotherapist, GP and, where useful, Versus Arthritis and BOA-endorsed support.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, physiotherapist or orthopaedic surgeon knows your knee and history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Osteoarthritis in over 16s: diagnosis and management (NG226).

  • British Association for Surgery of the Knee (BASK). Guidance on knee osteoarthritis and arthroplasty.

  • British Orthopaedic Association (BOA). Standards for knee replacement and revision surgery.

  • National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man - annual report.

  • Versus Arthritis. Patient information on knee osteoarthritis.

Red flags

When knee pain needs urgent attention.

Most knee osteoarthritis is manageable in primary and specialist musculoskeletal care. These are the situations where it is not.

  • Hot, swollen knee with fever

    Septic arthritis is a surgical emergency - urgent hospital assessment and joint aspiration are needed within hours, not days.

  • Sudden mechanical locking

    True locking suggests a meniscal flap or loose body - see our knee cartilage injury and knee meniscal tear guides and request specialist review.

  • Rest pain and night pain

    Osteoarthritis pain typically eases at rest. Persistent pain that wakes you from sleep needs a specialist opinion to exclude other causes.

  • Rapidly progressive symptoms

    Fast decline over weeks, rather than months to years, may suggest avascular necrosis, crystal disease (see our gout guide) or inflammatory arthritis.

  • Systemic features

    Weight loss, fevers or morning stiffness lasting more than an hour - think inflammatory arthritis rather than osteoarthritis and refer for rheumatology review.

  • Post-injury deformity

    A change in alignment after a fall or sports injury needs urgent orthopaedic review to exclude fracture or ligament rupture.

  • Neurovascular symptoms

    Calf swelling, pallor, pulselessness or foot drop after a knee event needs same-day assessment - see our carotid artery disease and DVT guidance for context.

  • Unexplained anaemia or bloods

    Anaemia, high inflammatory markers or unexplained bloods sit outside primary osteoarthritis - a specialist opinion is warranted.

  • Failed conservative care

    Persistent pain and loss of function despite optimised NICE first-line care is itself a signal to escalate to orthopaedics for consideration of surgery.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference day to day - strengthening, weight, pacing, and knowing when to step up.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits kept up for months do more than a heroic week that doesn\'t last.

  1. 01 Movement

    Keep the quadriceps strong

    A supervised strengthening programme is the single most effective self-management step - stick with it for at least 12 weeks.

  2. 02 Weight

    Every kilogram counts

    A 10% weight reduction produces a clinically meaningful drop in pain and disability. Specialist dietetics support helps it last.

  3. 03 Pace

    Pace, don't boom-and-bust

    Alternating heavy activity with days of pain is worse than steady, moderate movement. Plan the week, not just the day.

  4. 04 Escalate

    Know when to step up

    If pain limits work, sleep or independence despite first-line care, ask for orthopaedic review - osteotomy or knee replacement can transform outcomes.

Frequently asked

Everything we get asked about knee joint osteoarthritis.

Quick answers on diagnosis, NICE first-line care, injections and modern knee replacement.

  • What is knee joint osteoarthritis?

    Knee joint osteoarthritis (KOA) is a degenerative condition of the knee marked by progressive cartilage loss, subchondral bone sclerosis, osteophyte formation and low-grade synovitis. It is the most common cause of knee arthritis in the UK and typically presents with insidious pain, short morning stiffness, reduced range of movement and functional decline. See our knee arthritis guide for the wider picture.

  • How is it diagnosed?

    Diagnosis is clinical, supported by a specialist musculoskeletal examination and a weight-bearing X-ray graded with the Kellgren-Lawrence system. MRI is selective rather than routine - useful when a meniscal or ligament injury, avascular necrosis or an unusual pattern is suspected. An orthopaedic MDT reviews complex cases.

  • What does NICE recommend as first-line treatment?

    NICE NG226 places weight loss, structured exercise and specialist musculoskeletal physiotherapy at the foundation of care. Topical NSAIDs are the preferred medication, with paracetamol and short-course oral NSAIDs as adjuncts. Intra-articular steroid injections are considered for flares.

  • When is surgery considered?

    Surgery is considered when NICE-based first-line care no longer controls pain or maintains function. Options include high tibial osteotomy for younger patients with medial unicompartmental disease, unicompartmental knee replacement for isolated compartment wear, patellofemoral replacement for isolated kneecap arthritis, and total knee replacement - increasingly robotic-assisted - for tricompartmental or advanced disease.

  • What is the difference between unicompartmental and total knee replacement?

    A unicompartmental knee replacement resurfaces only the worn compartment (usually medial), preserving ligaments and unaffected cartilage. It offers faster recovery and a more natural feel in the right patient. A total knee replacement resurfaces all three compartments and remains the definitive option for widespread arthritis. Selection is guided by an orthopaedic MDT.

  • Are injections a long-term solution?

    Intra-articular steroid injections settle flares and can bridge symptoms while other treatments take effect, but they are not a long-term cure. Hyaluronic acid, PRP and orthobiologics are considered selectively in specialist clinics. If injections are needed repeatedly, that is a signal to review the wider plan and consider surgical options.

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