Some are! Avocados, tomatoes, etc....

Actually, he built in on a swamp. & it is slowly sinking......NOT floating!

Let's not forget all the other things that have a habit of going arse up in our 'DESIGNED by Gawd' bodies,
Eyes, Hearing, Hearts, Brains, Bones, Prostates in Men, Ovaries and Wombs in Women, Gastric Ulcers, the Appendix, the Reproductive Organs placed right beside a Sewage Outlet, Miscarriages, Still-births, Birth Defects, Menstruation, Menopause, Impotence, Jeez Louise the list is almost endless.

@Triphid true, all true, but even a drump-lover would not take one look at a knee & conclude the designer was drunk, at best

@AnneWimsey Yeah our knees wear out quite quickly but Anatomically our ankles are the weakest of all our joints.

@Triphid knock wood my ankles are still just fine. one knee replaced TWICE within 2 months, 3 dogs with 4 knee replacements, (Big $$$$!) All ankles just fine..........I think I had a sprained one in '87

@AnneWimsey Our ankles take about 50% EACH of our body weight with EVERY step we take, one wrong step and voila, either a Sprained ankle or even worse a Fractured Ankle.

@Triphid bah! I currently weigh about 80 lbs more than I should, for Years (ever since the 2nd knee replacement). Was at fighting weight when I sprained the ankle, by slipping down a stair-step.

@Triphid i was told needed one in my 40's, but was "too young" as the life expectancy of the device was about 25 years max. Limped, got cortisone injections, limped some more for 30 (!) years, still doing major DIY & all yard work. Until it was Do Something or go to assisted living. Had 3 delightful pain-free weeks immediately after the surgery, even refused all but a few Tylenol, major therapy fiend, then I knew something wasn't going well. it took 2+ more weeks for them to Listen to me. Now, after 3 years, mostly it hurts less than originally, but i cannot kneel, never will. This impacts DIY stuff Big-time. But I truly waited until something Had to be done. And BTW I also had a shoulder replaced, a Much bigger deal than a knee, it went beauifully

@Triphid You will know when you need to get your joints replaced, I have had both of my knees replaced. I suffered from habitual subluxating patellas from the age of about 8 possibly linked to a really rare condition that about 1 in 250,000 females can have.
By the age of 20 I had arthritis in both knees, at the age of 30 I finally found a surgeon who believed me about what was happening (I got told I had torn a tendon, had flaky cartlige, must have stepped wrong, needed to lose weight etc before then) He operated to stop the dislocating problem. He had worked on top rugby players and worked on aged service men.
At the age of 30 one of my knees was in the top three worse knees he had ever seen and the other was in the top 10.
At the age of 40is walking, and standing were painful and I started a regime of medication to control the pain (going up or down stairs was impossible) a few years later I was on a cocktail of drugs to control the pain,
There were days when once I got home from work and walked my dogs I stopped drinking any liquids as I was curled up on the couch in so much pain and could not take any more medication and if I drank then I would need to pee and I did not want to walk any more. I would drag myself to bed and slept with my legs elevated in the hope that it would help.
When I went to see the Surgeon knowing replacement was the only option (by this point I walked with a cane, could not stand at work for the national anthem at assemblies, and while I was walking my dogs in the morning, it was a short walk, hoped I would get mugged so I could take out my pain on someone who deserved it) he was surprised that I was walking.
There was pretty much no cartilage left and the bone was touching on one side of each knee. I had lower back pain from the way I was walking and a handicapped sticker for my car.

I had the first one replaced, when I stood up I thought my knee was collapsing backwards but got told no it was simply straight (my other leg I discovered I could not straighten any longer) when I was told to stand on my good leg I stood on the operated one as it caused less pain than the one still needing to be fixed. I have been told the surgery is painful but I was in less pain from the knee after the surgery than I was before.
I have now tried to learn to ski (I am a gumby so I can't) walk over a km without problems, climb stairs, and no longer take pain meds in fact I got a cold after both were done and was told to take panadol for the pain and had to go and buy some as I had none in the house. Prior I would have had stashes of it in my bag, the house, my car, at work, my work backpack, any place I could think I might need it. I was on tramadol, panadol osteo, disprin, celebrex, and from a very dear friend a botanical relief that was frowned upon by law enforcement.

I have now had about 10 years of pain free existence, you will know when you can no longer tolerate the pain when your quality of life is such that a wheelchair is looking a possibility because eating peanut butter sandwiches (something quick and simple to prepare that can be eaten lying down) is not a balanced diet.

@Budgie There was once a time, not so long ago, that I would, and could, walk miles and miles without even thinking about my knee, etc.
But age and "Uncle Artha" have taken their toll these days and my 'familiar' Sailor style walking gait, as my Dad used to call it, has become more like a 'Drunken Sailor....LOL.