I have been very active in outdoor recreation all my life. Rock climbing, hiking, skiing, etc. I used to do quite a bit of running as well (including a few ultra distance events). I was doing tons of vigorous activities (skiing, rock climbing, and hiking) with minimal pain right up until March of this year, when it swelled up unexpectedly while on an ice climbing trip. The swelling did not go away. X-rays showed "end stage arthritis, bone on bone" in my left knee. This was a total surprise to me. I didn't believe it. I waited a month, and went for a second opinion elsewhere. They confirmed the situation, and an MRI showed that the bone ends were inflamed. Complex tears of the meniscus, that probably happened as a youth (circa 1977), had caused that knee to wear out prematurely. I guess that I was lucky that it didn't hurt for those 40 years. But, it really hurt now! Preemptively, I went to a PT, for two months, which really helped in the long run. Getting as strong and flexible as possible before surgery really makes a difference. I couldn't hike at all, but I exercised and rode my mountain bike religiously for the 2 1/2 months before surgery. I had my left knee replacement on Sept. 25, 2018. I had various troubles while in the hospital (bladder retention, uncontrolled pain, reactions to certain meds, etc), but nothing too serious. I had been well warned that "you will be miserable for 6 weeks," and that came true. At 6 weeks, I had fairly good range of motion, but still lots of pain and swelling. I could walk without a limp (but in pain) across a parking lot, but still could not drive my stick shift. I tapered off of oxycodone in the sixth and seventh week (very uncomfortable). Now, at 9 weeks post op, I'm progressing slowly but steadily. I can hike a mile comfortably (but slowly). I go "foot over foot" up and down stairs without any assist (with mild pain). Riding a stationary bike for more than 10 minutes makes the knee swell up, as does standing still or hiking two miles. I ice twice a day, and use Voltaren/diclophenac cream, to keep the swelling reasonable. Elevating (really high!) that leg for an hour before bed seems to help a lot. My therapist measured me at 129/1 on a really good day when I wasn't very swollen. I'm the persistent/methodical/determined type and will be able to improve on that. I'm amazed at how much strength and endurance I lost in just two months. But, I'm hopeful that I can make a true comeback and do some things better than ever before. I've already started snowshoeing some, and am working towards being able to do indoor rock climbing within a month or so. Next year I hope to be climbing outdoors and hiking the Grand Canyon. I'm very open to questions, and will be posting my updates here.