Priority 9 from the Revision Knee Replacement PSP

UNCERTAINTY: What causes knee stiffness following knee replacement? How can it be avoided and how is it best treated? (JLA PSP Priority 9)
Overall ranking 9
JLA question ID 0093/9
Explanatory note Stiffness can cause significant distress and difficulty for patients following knee replacement, so we need to better understand the causes and what can be done to avoid this issue. In those in whom in is not avoidable, how can we best deal with the problem. 
Evidence

 None identified
Health Research Classification System category Musculoskeletal
Extra information provided by this PSP
Original uncertainty examples How to best treat persistent stiffness following knee arthroplasty. ~ following MUA for  post op pain and stiffness at what point do we advise no further surgery will help ? ~ I have stiffness and am having an MUA for stiffness - will this work? Will it come back after?  ~ Why do some patients have pain or stiffness? 
Submitted by See data spreadsheet on JLA website 
PSP information
PSP unique ID 0093
PSP name Revision Knee Replacement
Total number of uncertainties identified by this PSP. 32  (To see a full list of all uncertainties identified, please see the detailed spreadsheet held on the JLA website)
Date of priority setting workshop 21 May 2019