This page provides guidance on the appropriate use of imaging (X-ray, Ultrasound, MRI) for symptomatic knee conditions primary care.

Direct access for imaging

Modality

Indications

Comments

Xrays
  • Clinical suspicion of Knee osteoarthritis
  • Post-traumatic injury with potential fracture
  • Significant progression of known osteoarthritis
  • Should be requested as weight bearing views
  • See pathways for acute/recent knee injuries below

Ultrasound scans
  • Soft tissue mass

 

Not for

  • Baker’s cyst
  • Effusion requiring aspiration
  • Meniscus or ligament evaluation
  • Guided knee injections

MRI
  • True locking or mechanical symptoms following an injury**
  • Suspected serious Knee pathology (with redflag features)

** see pathway below

Clinical imaging guidance

  • Imaging is not routinely needed in initial assessment of most non-traumatic knee pain cases.
  • Imaging is not always helpful as it is common to find ‘abnormalities’ on x-ray, ultrasound and MRI scans in the asymptomatic population too.
  • It should only be requested in the instance that it would be likely to influence clinical management.
  • All patients should have been examined before any request for imaging is made.​​​​​​

Indications for Xrays in Primary care- It is the first-line imaging suggested in primary care. Weight bearing views to be requested.

 

Clinical suspicion of Knee osteoarthritis

Post-traumatic injury with potential fracture

Significant progression of known osteoarthritis

​​​​

Knee Red Flags

Clinical Pathway

Suspected Joint sepsis

Ref to A&E via Orthopaedics on-call

Suspected fracture

Referral to A&E

Suspected stress fractures

Fracture clinic

Suspected malignancy

Follow 2-week rule pathway

Ultrasound scans and MRI in primary care

The majority of patients who initially present in primary care with knee symptoms, no red flags and no history of acute knee injury or a locked knee do not need an ultrasound or MRI investigation. There are very limited indications for Knee MRI scans in primary care.

Indications for knee ultrasound scans
  • Soft tissue mass

Not for

  • Baker’s cyst
  • Effusion requiring aspiration
  • Meniscus or ligament evaluation
  • Guided knee injections

Clinical pathway for patients with acute/recent knee injuries

Problem

MRI in Primary Care

Referral destination

True locking or mechanical symptoms following an injury in patients whose X-rays are normal (no OA or sinister pathology)

Pseudo-locking (this is momentary stiffness with pain following a period of immobility)

True Mechanical symptoms include giving way, inability to extend the knee (locking in extension)

MRI in Primary care, provided

  • Xrays (in the last 12 months) do not show OA.
  • Patient should have true locking
  • Patient examined by person requesting the scan

 

UCC/Fracture clinic

Significant Knee injury (hemarthrosis, difficulty to weight bear) with true mechanical symptoms

No

 

Fracture Clinic/UCC/IMPReS

Patients with symptomatic knee pain/mechanical symptoms and previous meniscal surgery

No

 

Refer to IMPReS

Patients with persistent knee pain symptoms not improved after conservative management.

No

 

Refer to IMPReS

  1. National Institute for Health and Care Excellence (NICE).Osteoarthritis in over 16s: diagnosis and management. NICE Guideline [NG226]. October 2022. Available at: https://www.nice.org.uk/guidance/ng226 
  2. National Institute for Health and Care Excellence (NICE).​​​​​​​ Joint replacement (primary): hip, knee and shoulder. NICE Guideline [NG157]. February 2020. https://www.nice.org.uk/guidance/ng157
  3. Royal College of Radiologists (RCR).​​​​​​​iRefer: Making the best use of clinical radiology services. https://www.rcr.ac.uk/our-services/irefer
  4. British Medical Ultrasound Society (BMUS).​​​​​​​ Justification of Ultrasound Requests: Audit and Guidance Document. May 2022.​​​https://www.bmus.org/static/uploads/resources/BMUS_Justification_Doc_edit_May_2022.pdf
  5. Royal College of Radiologists (RCR).​​​​​​​ Radiography for knee trauma – compliance with the Ottawa Knee Rule. https://www.rcr.ac.uk/audit/radiography-knee-trauma-compliance-ottawa-knee-rule 
  6. Royal College of Radiologists (RCR).​​​​​​​ Major adult trauma radiology guidance. 2024. https://www.rcr.ac.uk/our-services/all-our-publications/clinical-radiology-publications/major-adult-trauma-radiology-guidance
  7. Lancashire and South Cumbria Integrated Care Board (ICB).​​​​​​​ Commissioning policies for criteria-based clinical procedures. https://www.lancashireandsouthcumbria.icb.nhs.uk/our-work/commissioning-policies ​​​​​​​
  8. NICE Clinical Knowledge Summaries (CKS).
    Knee pain – assessment. https://cks.nice.org.uk/topics/knee-pain-assessment/
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