As noted elsewhere in the forum, my father and at least two brothers and at least 2 neices also crack, but to a lesser degree than me. None of them share any of my listed symptoms. In chronological order:

Premature birth (6 weeks, considered extreme in 1962)
Pneumonia (stopped after age 6 or so)
Bronchitis (stopped after age 6 or so). Got ear tubes in at 6, out at 10.
Hyperactivity. Took amphetemines from ages 8 to 14. Shorter than
my brothers as a result.
Allergies to dust, fur, feathers, shrimp, peanuts, soy. I
don't avoid any of these. I have chronic sinus drip to my stomach.
Skin fungal infections (ages 16 to 24).
Prostate infections (ages 18 to 24). Stopped when I gave up beer.
Kidney stones (ages 40 and 43). Flared up when trying high-protein
diet to lose weight.
Lots of intestinal gas, but this is probably due to enjoying lots of fruit
and vegetables (along with everything else).
Overweight (gaining about 1.5 lbs per year since age 22)

I'm actually pretty happy. I rarely take medication for anything, just ibuprofen for pain after excercise. The cracking doesn't bother me, but I don't like the idea of paralysis or stroke due to neck cracking, so I try to keep up with the research every so often to see if anyone has any bright ideas. Of course, others are bothered so that is (slight) incentive to stop if a cure could be found for the stiffness and lack of mobility.

I also have a strong, repetitive desire to drink water, eat food, and go to the bathroom due to certain overwhelming signals from my body. Sorry for the sarcasm, but there seems to be an assumption inherent in much of this site that the desire to crack joints is somehow false or contrary to what is healthy.

Here are some things to consider:

1. Perhaps pressure inside the joint is bad. I work in the chemical industry, and relieving excess pressure from tanks and vessels is a requirement to prevent damage to them. An imperfect analogy, I know…
2. Perhaps the pressure is caused by some failure of the joint membranes that allows more gasses to migrate into the joint, and/or less gasses to migrate out. I would assume that the joint is alive, and therefore needs oxygen to be supplied and CO2 to be removed.
3. Alternatively, maybe there is something in the cracker's system that generates more gas inside the joint. Decomposition or other reactions of chemicals can give off gases.

On the other hand, maybe everyone has the same amount of dissolved gas, but different nerve sensitivity to the resulting pressure. Just as some people have sensitivity to noise or light levels that don't bother most humans, maybe crackers have extra sensitivity to pressure. I doubt this is a cause, since my body involuntarily cracks when I stretch, walk, etc. But, maybe I've just loosened up every joint in my body over the years because I have cracked them on purpose so many times due to heightened sensitivity....

My father and at least 3 of my four brothers crack many joints, mainly neck, knuckles, ankles, and back. We also have other common traits (all engineers with very high intelligence, all have green/blue eyes despite brown hair and easily tanned skin).

I have the worst cracking problems of all the family. My ankles crack whenever I wake up (involuntarily), and my range of motion becomes limited if I don't crack knuckles, neck and ankles several times per hour. The only joints that rarely crack are elbows, shoulders, and hips.

I was diagnosed with hyperactivity when a child (before ADHD was cool) and am now in my late 40s. Been cracking my neck since my early 20s, either by manual cranking or accelerated head-spinning. No paralyisis yet. My knees are starting to experience sharp pains. I am the only family member who is significantly (40 - 50 lbs) overweight.

My nieces crack knuckles. I have kids 3 and 6 and hear their joints crack from time to time during active play, but have tried to discourage any purposeful cracking on their part.

My brother got "treatment" for neck cracking for a while during Navy training that consisted of antidepressants. Seemed to help temporarily.

Not aware of any issues on my mother's side. My cousins/uncles aren't close so I haven't noticed/asked about their crack issues…..