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    Interventional procedure overview of radiofrequency denervation for osteoarthritic knee pain

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    Outcome measures

    The main outcomes included VAS, NRS, and WOMAC. The measures used are detailed in the following paragraphs.

    • The Kellgren-Lawrence system is used for classifying the severity of osteoarthritis by radiological findings. It ranges from 0 (no osteoarthritis) to 4 (severe osteoarthritis).

    • The VAS and NRS are similar instruments used to assess pain. The simplest VAS is a straight line of fixed length. The scale ranges from least pain to most pain and the participant marks the line corresponding to the level of pain they feel. A ruler is used to measure the distance from the end of the line to the participant's mark. Higher scores indicate worse pain. An NRS is a segmented, numeric VAS, in which participants rate their pain on an 11-point scale (0 to 10). NRS scores may be converted into VAS scores. MCID estimates vary, but an MCID of 1.99 cm (or 19.9 mm) has been reported for VAS and an MCID of 1 point or 15% has been reported for NRS.

    • The Global Perceived Effect scale is a scale used to assess the participant's perception of how their pain has changed after they have an intervention. It is typically a 7-point scale ranging from 1 – very much deteriorated, to 7 – very much improved.

    • The WOMAC is a self-administered, 24-item instrument. The WOMAC is subdivided into 3 components: pain, stiffness, and physical function. Higher scores indicate worse osteoarthritis-related health. MCID estimates vary, but an MCID of 11 points has been reported for people with knee osteoarthritis.

    • The Timed Up and Go test measures the time taken to rise from sitting on a standard chair, walk 3 metres in a straight line, turn around, walk back, and sit again.

    • The EQ-5D is an instrument used to assess health-related quality of life across 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The instrument also contains a VAS on general health.