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Health condition · Clinically reviewed

Knee pain, by cause, by pattern, and by what to do next.

A very common problem with many causes. The right plan begins with a clear pattern, a careful examination, and the right image at the right time.

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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, ARMA and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including MRI thresholds, MDT musculoskeletal pathways and staged surgical care.

Key facts

Knee pain at a glance.

The essentials in plain English: what causes knee pain, what to look for, and how it is worked up in the UK.

  • What it is

    A hub symptom, not a diagnosis. Pain arising from the knee joint, its soft tissues, the bone, or referred from the hip or lumbar spine.

  • How common

    Very common. Roughly one in four adults report significant knee pain in any given year across UK primary care.

  • Where it starts

    Anatomy is the map. Intra-articular, peri-articular, mechanical, referred, bone, nerve, inflammatory, post-traumatic or paediatric.

  • Red flags

    Hot swollen joint with fever, inability to weight-bear after trauma, unexplained night pain or systemic illness need urgent review.

  • Imaging

    Weight-bearing X-ray first for suspected osteoarthritis. MRI for internal derangement, cartilage, ligament or occult bone injury.

  • Care route

    MDT musculoskeletal: GP, physiotherapist, sports and exercise medicine, rheumatology and orthopaedic surgeon as needed.

Causes

An anatomical framework, so nothing is missed.

Group the causes by structure and origin. It keeps the differential honest and stops the assessment collapsing into a single label.

  • Intra-articular

    Osteoarthritis, meniscal tear, ligament injury, cartilage injury, loose body, synovitis, septic arthritis and crystal disease such as gout.

  • Peri-articular

    Bursitis, Baker cyst, patellofemoral pain syndrome, patellar and quadriceps tendinopathy.

  • Mechanical

    Patellar instability and maltracking, often with a history of dislocation or generalised joint laxity.

  • Referred

    Hip osteoarthritis and lumbar spine pathology can present as knee pain, especially anterior or medial.

  • Bone

    Stress fracture, osteochondritis dissecans, osteonecrosis and, rarely, primary or secondary bone tumours.

  • Nerve

    Saphenous and common peroneal nerve entrapments produce specific patterns of pain and altered sensation.

  • Inflammatory

    Rheumatoid arthritis, spondyloarthropathy and juvenile idiopathic arthritis. Suspected when stiffness and multi-joint features are present.

  • Post-traumatic

    Persistent pain, stiffness or instability after injury or surgery, including complex regional pain syndrome.

  • Paediatric

    Osgood-Schlatter and Sinding-Larsen-Johansson disease in growing athletes. A paediatric orthopaedic opinion when in doubt.

See our detailed guides on knee osteoarthritis, knee arthritis, meniscal tears, ligament injury, cartilage injury, bursitis, tendinopathy, gout and hip arthritis.

How the diagnosis is made

From first visit to a clear plan.

The steps a UK GP, physiotherapist or knee specialist will usually follow, in order, so you know what to expect and why.

  1. 01

    Assessing

    History and mechanism

    When it started, how it started, what makes it worse, what helps. Twist versus overload versus insidious onset tell very different stories.

  2. 02

    Assessing

    Red flag screen

    Fever, hot swollen joint, night pain, weight loss, cauda equina symptoms, inability to weight-bear after trauma. These change the pathway immediately.

  3. 03

    Assessing

    Structured examination

    Gait, alignment, effusion, range, patellar tracking. Specific tests: McMurray, Thessaly, Lachman, pivot shift, varus and valgus stress.

  4. 04

    Confirming

    Hip and spine review

    Knee pain is often referred. A short hip and lumbar exam catches the cases where the knee is a symptom, not the source.

  5. 05

    Confirming

    Weight-bearing X-ray

    The first-line image for suspected osteoarthritis, alignment, joint space loss and loose bodies. Standing views change the yield.

  6. 06

    Planning

    MRI when indicated

    For suspected meniscal or ligament injury, cartilage lesions, occult fracture or persistent pain despite treatment. See our private MRI guide.

  7. 07

    Planning

    MDT and specialist referral

    Musculoskeletal physiotherapy, sports and exercise medicine, rheumatology or orthopaedic surgery, matched to the underlying cause.

Typical timeline: a settled plan within one to two visits, with imaging arranged where it changes management.

Symptoms

What knee pain actually looks like.

The patterns that matter, and the features that mean it is time to escalate rather than wait.

  • Aching front of knee

    Classic pattern of patellofemoral pain and early osteoarthritis. Worse on stairs, hills, and after long sitting.

  • Sharp catching or locking

    Suggests meniscal tear, loose body or cartilage flap. Warrants imaging and a specialist opinion.

  • Giving way

    A knee that buckles points to ligament injury, quadriceps inhibition or patellar instability.

  • Swelling

    Rapid swelling within hours after trauma suggests haemarthrosis and ACL rupture. Slower swelling suggests effusion.

  • Warmth and redness

    A hot, red, tender knee with systemic symptoms is septic arthritis until proven otherwise. Same-day review.

  • Morning stiffness

    Prolonged early morning stiffness raises the possibility of inflammatory arthritis rather than mechanical pain.

  • Pain behind the knee

    Suggests Baker cyst, hamstring tendinopathy, or referred pain. Sudden calf swelling needs a DVT review.

  • Red flag pattern

    Hot swollen joint, night pain, unable to weight-bear, systemic illness or new neurological signs need urgent assessment.

Treatment

How knee pain is treated in the UK.

Rehabilitation first, targeted injections and shockwave where indicated, and surgical care for specific structural problems.

  • Load management and physiotherapy

    The single biggest lever for most knee pain. Progressive strengthening, gait retraining and pacing beat rest.

  • Analgesia, staged

    Paracetamol, topical or oral NSAIDs where safe, and short courses of stronger analgesia only when clearly justified.

  • Weight and activity plan

    For osteoarthritis, modest weight loss reliably reduces load and pain. Low-impact aerobic work adds real benefit.

  • Bracing and orthoses

    Patellar taping, unloader braces or a foot orthosis can help specific patterns of maltracking, instability or malalignment.

  • Steroid injection

    For flares of osteoarthritis, bursitis or synovitis. Short-term benefit and a valuable bridge to rehabilitation, used judiciously.

  • Shockwave therapy

    A useful option for stubborn patellar and quadriceps tendinopathy alongside a graded loading programme.

  • Arthroscopic surgery

    Targeted for specific meniscal, cartilage or loose-body problems. Not a first-line answer for uncomplicated osteoarthritis.

  • Knee replacement

    For end-stage osteoarthritis after non-surgical care has been tried. Partial or total, planned with an orthopaedic surgeon.

See related treatment guides: knee replacement, steroid injection, shockwave therapy, musculoskeletal physiotherapy, private MRI scan and private ultrasound scan.

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 knee specialist knows your history and examination and can tell you which parts apply to you. If in doubt, get seen.

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

  • NICE. Knee pain: assessment and diagnostic pathways in primary care.

  • British Orthopaedic Association (BOA). Standards for trauma and elective knee care.

  • ARMA. UK musculoskeletal core standards for MDT pathways.

Red flags

When knee pain needs urgent attention.

Most knee pain is manageable in primary care. These are the presentations where waiting is the wrong answer.

  • Septic arthritis

    A hot, red, swollen, exquisitely tender knee with fever or systemic illness. Same-day orthopaedic review and joint aspiration.

  • Fracture after trauma

    Inability to weight-bear four steps or bony tenderness after a fall or twist. Needs prompt X-ray using the Ottawa knee rules.

  • Neurovascular compromise

    Cold, pale, pulseless or numb limb after a dislocation or high-energy injury is a limb-threatening emergency.

  • Bone tumour signs

    Persistent night pain, unexplained swelling, a palpable mass or systemic symptoms warrant urgent imaging and specialist review.

  • Cauda equina symptoms

    New saddle numbness, bladder or bowel change with leg pain is a spinal emergency, not a knee problem.

  • Deep vein thrombosis

    Unilateral calf swelling, warmth and tenderness after immobility or surgery. Same-day Wells score and D-dimer or scan.

  • Osteonecrosis

    Sudden severe medial knee pain, often at night, in older adults or those on steroids. Early MRI is diagnostic.

  • Inflammatory arthritis

    Prolonged morning stiffness, multiple joints, systemic features or a family history need a rheumatology opinion.

  • Paediatric red flags

    A limping child with hip or knee pain, fever, or systemic illness needs paediatric orthopaedic assessment the same day.

Living with it

A treatable problem, with a clear ladder.

Four things that make the biggest difference day to day: graded movement, quadriceps strength, sensible weight and activity, and knowing when to ask for more.

A quiet reminder

Consistency beats intensity, every time.

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

  1. 01 Move

    Motion is medicine

    Most knee pain improves faster with graded activity than with rest. A physiotherapist can pitch the load right.

  2. 02 Strength

    Strong quads change everything

    Quadriceps and hip strength protects the joint and reduces pain across almost every cause. Small daily doses win.

  3. 03 Weight

    Small changes, real difference

    For osteoarthritis, a modest change in body weight reliably reduces pain and slows progression.

  4. 04 Escalate

    Know when to ask

    If pain, locking, giving way or swelling persist beyond a few weeks of sensible care, ask for imaging and a specialist opinion.

Frequently asked

Everything we get asked about knee pain.

Quick answers on causes, when to be seen, imaging thresholds and surgery.

  • What causes knee pain?

    The knee is the sum of a joint, ligaments, tendons, bursae, cartilage, bone, nerves and referral from the hip and spine. Common causes include osteoarthritis, meniscal tears, ligament injury, patellofemoral pain, bursitis, tendinopathy and, less often, inflammatory arthritis or referred pain. A careful history and examination narrows the list quickly.

  • When should I see someone about knee pain?

    Book a review if pain lasts more than two to three weeks, limits daily activity, or is associated with swelling, locking, giving way, or a recent injury. Same-day review is needed for a hot swollen joint with fever, inability to weight-bear after trauma, or new numbness and weakness.

  • Do I need an MRI scan for knee pain?

    Not usually at first. Weight-bearing X-ray is the standard first image for suspected osteoarthritis. MRI is reserved for suspected meniscal or ligament injury, cartilage damage, occult fracture, or persistent pain despite sensible care. Our private MRI guide sets out how it is used.

  • Can knee pain come from somewhere else?

    Yes. Hip osteoarthritis and lumbar spine problems can present as knee pain, particularly on the medial or anterior surface. That is why a brief hip and spine screen belongs in every knee assessment.

  • Is running bad for my knees?

    For most people it is not. Regular recreational running is associated with lower rates of knee osteoarthritis than sedentary living. Sudden increases in load, poor recovery and unmanaged prior injuries are the real risk factors.

  • When is knee replacement the right answer?

    When end-stage osteoarthritis produces pain and functional loss that non-surgical care cannot control. That means physiotherapy, weight and activity work, analgesia and, where appropriate, injections have all been tried. It is a planned decision, not a first response.

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