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Health condition · Clinically reviewed

Knee arthritis, from lifestyle and injections to robotic knee replacement.

An umbrella hub covering osteoarthritis, rheumatoid, seronegative, crystal, septic and post-traumatic forms - and the stepped UK pathway from first ache to definitive surgery.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

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

  • 02

    Sourced from guidance

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

  • 03

    Current for 2026

    Reflects modern UK practice including robotic-assisted knee replacement, partial knee options and specialist commissioned pathways.

Key facts

Knee arthritis at a glance.

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

  • What it is

    A group of joint diseases that inflame or wear the knee - osteoarthritis, rheumatoid, seronegative, crystal, septic, post-traumatic and rarer causes.

  • Most common form

    Osteoarthritis - primary age-related, or secondary to previous meniscal, ligament or malalignment injury. See our dedicated knee osteoarthritis guide.

  • Inflammatory forms

    Rheumatoid, psoriatic, ankylosing spondylitis and reactive arthritis - specialist rheumatology-led care with DMARDs and biologics.

  • Emergency form

    Septic arthritis - a hot, swollen, immobile knee with fever needs same-day orthopaedic assessment. This is a specialist commissioned pathway.

  • Crystal disease

    Gout and pseudogout (CPPD) - joint aspiration for crystals is the diagnostic step.

  • Definitive surgery

    Total or partial knee replacement - now often robotic-assisted (Mako) in specialist commissioned centres. See our knee replacement guide.

Types of knee arthritis

Not one disease - many.

The word "arthritis" covers a family of conditions. Getting the type right shapes every next decision.

  • Osteoarthritis (OA)

    The most common form - primary age-related wear, or secondary to previous meniscal or ligament injury or malalignment. See our dedicated knee osteoarthritis guide.

    Read more

  • Rheumatoid arthritis

    A symmetrical inflammatory arthritis driven by immune dysregulation. Rheumatology-led with DMARDs and biologics.

  • Seronegative spondyloarthritis

    Ankylosing spondylitis, psoriatic arthritis and reactive arthritis - HLA-B27 associated, often with skin, eye or spinal features. See our ankylosing spondylitis guide.

    Read more

  • Post-traumatic arthritis

    Wear after fractures, meniscal loss or ligament injury - often in younger patients. See our knee meniscal tear and knee ligament injury guides.

  • Septic arthritis

    Bacterial infection in the joint - a hot, swollen, immobile knee with fever. An emergency and a specialist commissioned pathway.

  • Crystal arthritis

    Gout (monosodium urate) and pseudogout (calcium pyrophosphate, CPPD) - sudden, severe flares diagnosed on aspiration. See our gout and calcium crystal disease guides.

  • Haemophilic arthropathy

    Recurrent bleeds in inherited clotting disorders damage cartilage over time. See our haemophilia guide.

  • Infection-related

    Tuberculosis, Lyme disease and reactive arthritis - rarer but important, with specialist infectious diseases input.

  • Juvenile idiopathic arthritis

    Inflammatory arthritis starting in childhood - paediatric rheumatology-led, sometimes carried into adulthood.

  • Neuropathic (Charcot) joint

    A grossly deformed, relatively painless knee in diabetes or peripheral neuropathy - a specialist commissioned pathway.

How the diagnosis is made

From first ache to a clear plan.

The steps a UK GP, orthopaedic surgeon or rheumatologist will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    History and red flags

    Pattern of pain, stiffness, swelling and function loss - and the red flags (fever, hot joint, trauma, systemic upset) that change the pathway.

  2. 02

    Assessing

    Examination of the knee

    Joint line tenderness, effusion, stability, range of motion, crepitus and gait - plus FADIR and FABER for hip-referred pain. Specialist orthopaedic input where needed.

  3. 03

    Assessing

    Weight-bearing X-ray

    The first-line image for osteoarthritis - joint space loss, osteophytes and alignment are only seen properly under load.

  4. 04

    Confirming

    Selective MRI

    Reserved for suspected meniscal or ligament injury, avascular necrosis or early inflammatory disease. See our private MRI scan guide.

  5. 05

    Confirming

    Joint aspiration

    For a hot, swollen knee - Gram stain and culture rule out sepsis, and polarised microscopy identifies urate or CPPD crystals. Emergency in suspected septic arthritis and a specialist commissioned pathway.

  6. 06

    Planning

    Serology and blood tests

    Rheumatoid factor, anti-CCP, ANA, HLA-B27, serum urate and inflammatory markers when an inflammatory or crystal cause is possible. Specialist rheumatology interpretation.

  7. 07

    Planning

    MDT plan

    Specialist orthopaedic, rheumatology and physiotherapy input agree on a stepped plan - lifestyle, medication, injection, DMARD or surgery. Specialist commissioned care where indicated.

Typical timeline: first visit to a settled plan in weeks, not months - faster in emergencies.

Symptoms

What knee arthritis actually feels like.

The classic mix of pain, stiffness, swelling and lost function - and the features that mean specialist review, not a wait-and-see plan.

  • Pain that changes with load

    Weight-bearing pain, worse after activity, is typical of osteoarthritis. Rest and night pain suggest an inflammatory or septic process.

  • Morning stiffness

    Under thirty minutes is usually mechanical. Over an hour, worse after rest, points to rheumatoid or seronegative disease.

  • Swelling and effusion

    A persistent effusion needs assessment - aspiration if hot, tense or associated with fever. Specialist input where needed.

  • Reduced range of motion

    Loss of full extension or flexion is common in advanced disease and a key driver of function loss.

  • Crepitus and giving way

    Grinding, catching or a sense of instability - often reflects cartilage or meniscal loss and needs assessment.

  • Altered gait

    A limp, varus (bow-leg) or valgus (knock-knee) posture points to compartmental wear and specialist orthopaedic review.

  • Systemic features

    Fatigue, weight loss, psoriasis, uveitis or bowel symptoms often mean an inflammatory arthritis - specialist rheumatology referral.

  • Red flag - hot, immobile knee

    A hot, swollen, painful knee that will not move, especially with fever, is septic arthritis until proven otherwise. Same-day specialist orthopaedic assessment.

Treatment

How knee arthritis is treated in the UK.

A stepped ladder under NICE and BOA guidance - lifestyle first, then medication and injection, disease-modifying therapy for inflammatory forms, and surgery when function fails.

  • Lifestyle and weight

    Weight loss and quadriceps-focused exercise change every downstream option - foundational for osteoarthritis and inflammatory disease alike.

  • Physiotherapy

    A structured programme of strength, range and gait retraining. See our physiotherapy guide for how it is delivered.

  • Analgesia and topicals

    Paracetamol, topical NSAIDs and short-course oral NSAIDs (with gastric protection) form the first medical step under NICE guidance.

  • Intra-articular steroid

    A steroid injection can settle a painful flare and buy time - useful in osteoarthritis, crystal disease and inflammatory joints. See our steroid injection guide.

  • Hyaluronic acid or PRP

    Selective options in osteoarthritis - evidence is mixed, and they are not funded routinely. Discuss risks and expected benefit.

  • DMARDs and biologics

    For rheumatoid, psoriatic and other inflammatory arthritis - specialist rheumatology-led, disease-modifying and often long-term.

  • Partial knee replacement

    Unicompartmental replacement for isolated compartment wear - shorter recovery and better knee kinematics in the right patient. See our unicompartmental knee guide.

  • Total knee replacement

    The definitive operation for advanced disease - open, minimally invasive or robotic-assisted (Mako) in specialist commissioned centres. See our knee replacement guide.

Joint-preserving surgery

High tibial osteotomy (HTO)

In younger patients with wear on the inner (medial) compartment and a varus deformity, a high tibial osteotomy realigns the shin bone to unload the damaged side and delay the need for a replacement. It is a specialist commissioned procedure. See our high tibial osteotomy guide.

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, rheumatologist 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).

  • NICE. Rheumatoid arthritis in adults: management (NG100).

  • British Orthopaedic Association (BOA). Standards for knee arthroplasty.

  • British Society for Rheumatology. Guidelines on DMARDs, biologics and gout.

  • Versus Arthritis. Patient information on knee arthritis and joint replacement.

Red flags

When a sore knee needs urgent attention.

Most knee arthritis is managed in primary and outpatient care. These are the situations that are not - and where a specialist opinion is needed quickly.

  • Hot, swollen, immobile knee

    Septic arthritis until proven otherwise, especially with fever or systemic upset. Same-day specialist orthopaedic assessment and aspiration - a specialist commissioned emergency pathway.

  • Fever and joint pain

    New fever with any single hot joint is a red flag - do not delay assessment while trialling anti-inflammatories.

  • Sudden locked knee

    A knee that will not straighten after twisting or a fall suggests a displaced meniscal tear. See our knee meniscal tear guide - specialist orthopaedic review is needed.

  • Post-traumatic pain and instability

    Giving way after injury, or persistent post-traumatic pain, points to ligament or cartilage damage. See our knee ligament injury guide.

  • Progressive deformity

    Worsening bow-leg or knock-knee posture with pain - specialist orthopaedic input and consideration of osteotomy or arthroplasty.

  • Rheumatoid or seronegative features

    Prolonged morning stiffness, small-joint involvement, psoriasis, back pain or uveitis - specialist rheumatology referral.

  • Recurrent gout attacks

    More than one or two attacks a year, or tophi - specialist review and urate-lowering therapy. See our gout guide.

  • Neuropathic (Charcot) joint

    A grossly deranged, relatively painless knee in diabetes or neuropathy - a specialist commissioned pathway with orthopaedic and diabetes teams.

  • Haemophilic arthropathy

    Recurrent bleeds into the knee - haematology and orthopaedic joint care. See our haemophilia guide.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference day to day - movement, weight, pacing, and knowing when to escalate for specialist review.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits - kept up for months - do more for an arthritic knee than a heroic week that does not last.

  1. 01 Move

    Motion is medicine

    Regular low-impact activity - walking, cycling, swimming - preserves range and strength. Rest flares, but do not rest the joint into stiffness.

  2. 02 Weight

    Small losses, big returns

    Every kilogram lost reduces knee load by around three to four kilograms per step. It is the single most powerful non-surgical lever.

  3. 03 Plan

    Pace and plan the day

    Break heavy tasks into shorter bouts, alternate loading with rest, and use aids without embarrassment - sticks, braces and shoe changes all help.

  4. 04 Escalate

    Ask for the next step

    When function limits your life - stairs, sleep, work - specialist orthopaedic review for partial or total knee replacement is reasonable.

Frequently asked

Everything we get asked about knee arthritis.

Quick answers on types, imaging, injections and knee replacement.

  • What is knee arthritis?

    An umbrella term for any inflammation or degeneration of the knee joint. The most common form is osteoarthritis, but it also includes rheumatoid, seronegative (psoriatic, ankylosing spondylitis, reactive), crystal (gout and CPPD), post-traumatic, septic, haemophilic and neuropathic forms. Each has a different investigation and treatment pathway.

  • How is the type of arthritis diagnosed?

    From a mix of history, examination, weight-bearing X-ray, and - selectively - MRI, joint aspiration for crystals or infection, and blood tests including rheumatoid factor, anti-CCP, ANA, HLA-B27 and serum urate. A specialist orthopaedic or rheumatology team leads more complex cases.

  • When is a knee replacement the right option?

    When advanced disease limits daily life - pain at night, difficulty on stairs, loss of independence - and non-surgical measures no longer help. Modern options include partial (unicompartmental) knee replacement and total knee replacement, increasingly performed with robotic assistance (Mako) in specialist commissioned centres.

  • What is a high tibial osteotomy?

    A joint-preserving operation for younger patients with wear on one side of the knee and a varus (bow-leg) deformity. It realigns the shin bone to shift load onto the healthier compartment and delays the need for a replacement - a specialist commissioned procedure. See our high tibial osteotomy guide.

  • Can I have a steroid injection?

    Yes - intra-articular steroid injections can settle a flare of osteoarthritis, inflammatory arthritis or crystal disease. They are not a long-term strategy, and repeated injections into the same joint are limited. See our steroid injection guide.

  • What warns me it might be septic arthritis?

    A hot, swollen, extremely painful knee that will not move, usually with fever or feeling systemically unwell. This is an emergency - go straight to A&E or contact your specialist team the same day. It is a specialist commissioned pathway with urgent aspiration and washout.

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