I would say honestly that it depends on how bad one's OA pain is and how much it interferes with one's life; and on the knowledge that OA pain only gets worse but TKR recovery pain gets better. I wouldn't mince words--of all the surgeries I've had, it's been the one that hurt the most and took the longest from which to recover. But except for the joy of producing a wonderful son after a C-section, it's also the one with the best results I've ever had.
I had been told in "knee class" before my RTKR that the pain would be much worse and recovery much longer than for a hip replacement, but nobody gave me any other benchmarks by which to measure the pain. And that's as it should be: not only is everyone different, but every knee is different. I have a notoriously low pain threshhold--in all honesty, had I been willing to use braces, canes, and NSAIDs (which tore up my guts) I could have gone a few years longer before my TKRs. But I was not willing to put up with the uncertainty of being fine one hour and suddenly swollen and limping (or either collapsing or locking up) the next, much less from day to day.
My "aha!" moment came during the Bar Show 2011. The director knew I was a klutz, obese and had knee pain (heck, she does too but has lousy insurance)--what kept me in the cast was my comedic & singing ability. She worked with the choreographer to ensure I would not have to kneel, jump or anything high-impact. (A veteran of two arthroscopies, I was already wearing a neoprene sleeve on my right and an off-loader brace on my left knee). But there was one number in which I was in the small backup quartet, in which we had to stand on a small platform and lean toward the leads by bending one knee and then gently bouncing up & down on our knees in time to the music (and I do mean gently as well as slowly). I was practically in tears after only one or two stanzas, and had to be helped off the platform by one of my castmates. It was then that I knew it'd be my last year with only the knees with which God brought me into this world. At the last after-party of the run, another castmate saw me with icebags on each knee, legs resting on a coffee table in the cast suite. I learned from her that her husband was an OS specializing in joint replacement; and from online research that he was one of Chicago's best. He advised doing the right first due to more bone complications.
People at knee class who'd had one TKR advised me to expect "two weeks of hell." My post-RTKR experience was more like 3 days of hell plus 11 days of heck. I did not do pre-hab--I dropped the ball and failed to register for it in time. I was also nearly 40 lbs. heavier than I am now. I did all the prescribed post-op rehab (inpatient, home, outpatient) and most of the home exercises. At 6 weeks I was driving 125 mi. nonstop; at just under 12 weeks I was on a plane to a European river cruise. The on-shore walks were tougher on my hips, feet and stamina than on my knees. The 2012 Bar Show was much easier on my right knee (probably because by then its quad was extremely strong) though the left was beginning to collapse and lock more often (due to having relied on it more during recovery). That offloader brace was not an option, as it clashed with my costumes; and by Jan. I had torn my left lateral meniscus climbing into a truck so there was nothing painless to which to "offload" my L medial knee pain. Same OS, but had to use a different hospital lest I face a 3-6-mo. longer wait for the LTKR. And I learned I had a chemically-induced ulcer caused by oral NSAIDs.
This time, lost 30 lbs. on a high-protein/low-carb diet, and did the full pre-hab. Also got a stash of Norco 5s from my FP just in case. I was sure that the LTKR would be easier. It wasn't--though the new hospital's pain control dept. was amazing, the rehab center's wasn't (and it was on doctors' orders due to new U.S. opioid and acetaminophen guidelines). This rehab center was better than last year's: more joint-oriented, great food, and companionship from fellow patients with whom I could socialize in a real dining room and over movies and ice cream. Twice the inpatient PT and OT as last year. But the PT was tougher.
Comparing the two? At 2 months out, each knee is equal to where the other one was at the same point in time. Biggest difference is that both my legs are now the same length and straight--so I can walk without hip pain and less foot pain as well compared to this time last year. (Had I the time & $ to repeat last yr's cruise, I'd doubtless do better now--especially since I learned a lot more about proper footwear for my anatomy and am now 40 lbs. lighter). Although I started off my LTKR rehab in more pain, I was able to wean off the opiods 2 weeks faster this time. I am convinced that it's not just the weight loss and prehab that made the ultimate difference but also the fact that I'd been eating much more protein--which aids healing and muscle-building. So why was my early LTKR recovery more painful? Turns out there was a lot of varus correction to do--and I had some exceedingly arduous PT in rehab before I was switched to a more understanding therapist.
But here's a dirty little secret: I have had a 3-week kneecation from PT (due to first a backache and then travel). Yet my flexion is drastically improved and I can use an exercise bike again to its full extent.
Let me also say that I was lucky painwise when a car shattered my leg in '96--the shock and worry kept the pain at bay and then the hospital hooked me up to the PCA-morphine pump pre-and-post-op. When it came to the pain of childbirth--my labor did not progress fast enough (though it began prematurely) so I had a C-section with an epidural. BUT the TKR pain at its worst (both times) was not as bad as the dysmenorrhea I suffered well into my 20s and 30s before NSAIDs came on to the market (and when doctors didn't prescribe codeine & the like for "mere menstrual cramps"). Gentlemen, sorry I can't offer you a comparison. In your defense, I have never had a kidney stone, shingles, or been kicked in my genitalia (which we ladies keep in our interiors for just that reason
). IMHO, the doctors who discovered NSAIDs and birth control pills could reduce menstrual cramps from agony to annoyance should have been granted the Nobel Prize long ago.
Do I regret having my TKRs a year apart rather than a BTKR? Well, despite the latter not being an option acc. to my OS due to both age and obesity, no. All in all, despite having gone through this twice I'm glad I had a comparatively "good leg to stand on" each time. I salute all of you who've had to rehab and recover from two knee replacements at once--I know I couldn't have done it.
But here's another maxim that should be a Bonesmart Mantra: your mileage may vary. I'd say only YOU know your capacities, strengths, weaknesses and fears. But I will say that my experiences have made me realize I'm stronger (physically and emotionally) than I ever thought I could be.
United States
I could choose to be bitter and miserable the rest of my life, or choose to get out and start living and that's what I am doing! I graduate in December w my Master's that I started after my knee replacements, and I have maintained an "A" average, I have lost 153 pounds, I workout harder than anyone else at the gym and I love it! 
I have down days, but I realize there are people that are always in worse shape than I am and I get back to the business of living!
I could hear and feel crunching, but back then you didn't dare complain to the coach, or they would replace you!
