Value of knee imaging by GPs requires rigorous assessment

Editor—In his editorial McNally reports that magnetic resonance imaging has had a great effect on the management of internal derangement of the knee and is increasingly available to hospital specialists and general practitioners.¹ Whether general practitioners' access to imaging has as great an effect as use by a knee specialist, however, is not known.² This question is crucial to patient management and outcome, and thus to cost effectiveness.

Access to magnetic resonance imaging by general practitioners for patients with knee problems could result in early diagnosis. Negative results could allow general practitioners to reassure patients, treat them conservatively, and avoid unnecessary hospital referrals, surgery, and associated costs. Positive results could confirm general practitioners' clinical diagnoses and ensure that urgent cases are seen more quickly by hospital specialists.³ This would ensure that surgeons were more likely to see patients who would benefit from a consultation, with the potential to reduce average waiting times, increase efficiency, and even improve patient prognosis and quality of life.

Although magnetic resonance imaging allows accurate assessment of meniscal and ligamentous injuries and avoids expensive invasive arthroscopy,²,⁴ no rigorous evidence shows whether it improves patient quality of life and reduces costs. The variation in general practitioners' access to, and use of, such imaging is also wide.⁵ This variation has been politically driven rather than evidence based, as the distribution of scanners reflects the past demands of fundholding general practitioners. So it is timely to ask whether access to this reliable diagnostic tool in primary care can achieve its potential.

The Medical Research Council has recently funded a multicentre randomised trial to help resolve the uncertainty about whether general practitioners should refer patients with internal derangement of the knee for magnetic resonance imaging or directly to an orthopaedic surgeon. We shall recruit 500 patients from over 250 general practices in north Yorkshire, north Wales, and north east Scotland and follow them up over 24 months. The trial will inform policy on whether to increase open access for general practitioners or to restrict magnetic resonance imaging to secondary care at the request of orthopaedic surgeons.

As McNally describes, magnetic resonance imaging of the knee is accurate and can help inform therapeutic decisions. But its use is already consuming substantial NHS resources without evidence of whether it improves patient outcome. Access to magnetic resonance imaging by general practitioners is at risk of becoming standard policy without rigorous evaluation.