Table 1 Attrition from screening to enrolment

 196 ineligible

  46 listed for surgery under private healthcare

  37 listed for revision rather than primary TKA

  27 due to undergo bilateral synchronous TKA

  24 not a participating surgeon

  23 auto-immune inflammatory joint disease

  16 BMI > 40

  8 co-existent medical problem

  4 screened before official study start date

  3 inability to provide informed consent

  3 listed for NHS waiting list Saturday surgery

  2 cognitive reasons

  2 not listed for primary TKA

  1 fixed motor deficit

 164 initially eligible but 22 not given study information or approached

  15 recruitment closed

  7 surgery time changed so unable to approach

 142 were sent a patient information sheet and 42 had no further contact or approach

  10 recruitment had closed

  8 surgery cancelled or time changed

  7 surgeon not participating

  7 no staff available to approach

  3 listed for NHS waiting list Saturday surgery

  3 discovered BMI > 40

  2 listing changed to private healthcare

  1 fixed motor deficit

  1 deceased

 100 patients contacted or approached: 21 declined and 25 discovered ineligible

  8 surgeon not participating

  5 surgery cancelled or time changed

  3 listed for bilateral synchronous TKA

  3 discovered BMI > 40

  2 inability to provide informed consent

  1 fixed motor deficit

  1 listed for complex TKA

  1 listing changed to private healthcare

  1 listed for NHS waiting list Saturday surgery

 54 enrolled

  14 withdrawn due to intra-operative finding of non-inflamed synovium

  40 randomised and followed up