Table 1

Attributes and levels included in the discrete choice experiment

AttributesLevelsVariable coding for analysis
Pain outcomes:
1. Daytime pain 9–12 months after surgeryNone
Moderate
Severe
Dummy variable – ‘severe daytime pain’ was the omitted reference group
2. Night-time pain 9–12 months after surgeryNone
Moderate
Severe
Dummy variable – ‘severe night-time pain’ was the omitted reference group
Functional outcomes:
3. Standing and walking on a flat surface 9–12 months after surgeryNo difficulty
Moderate difficulty
Severe difficulty
Dummy variable – ‘severe difficulty standing and walking’ was the omitted reference group
4. Bending to the floor, rising from sitting and going up and down stairs 9–12 months after surgeryNo difficulty
Moderate difficulty
Severe difficulty
Dummy variable – ‘severe difficulty bending from the floor, rising from sitting and going up and down stairs’ was the omitted reference group
Risk of complications:
5. Risk of having to go back into hospital and have a second operation on your knee (eg, due to knee stiffness, wound/joint infection)0%, 7%, 13%Continuous
6. Risk of getting a complication that requires seeing your GP or specialist for further treatment (eg, blood clot, skin infection, confusion)0%, 10%, 21%Continuous
  • GP, general practitioner.