I hurt now.

Okay, I'm going to assume your joints are hurting right now, and I'm going to assume it's your knees.  (From what I have seen and gathered over the years, it usually starts with knees, then ankles/hips)
You've been trying to tough it out for a while but it's just not going away.  And you don't know what to do or where to start.  If you're hurting now, read on.

1.  First of all, I wish someone had told me this at the beginning:  Your joint pains are here to stay and it's a Looooooooong road to recovery.  Tendons, connective tissues and cartilages take many months to heal.  I had to spend many many many months trying to wait it out (biting my lips while working 3 jobs), crying from the defeat of pain and feeling lost before I finally realized it's not something I can get over like a cold, and had to adapt a completely different attitude and lifestyle.  Get in the new life-planning mode, get off the bed/sofa, and start making changes every day.

2.  Go to a swimming pool now!!  Get a membership and go everyday if possible.
Being in the water is the best (and possibly the only) thing you can do to get relief from joint pain to promote healing, be able to exercise, so you can eventually get your mobility back.
You don't even have to be able to swim, just go float/walk around in the chest-level water.  (If you still feel your knees aching, wear the Jog Belt and float around in the deep end.  It may look dorky, but the relief is sweet sorrow..)

This dorky belt helps you to float upright so you can feel the complete relief on your knees, while making your abs work.  Not so dorky now, is it?

photo from SwimOutlet.com

I like to do the crawl & backstroke laps with Pull Bouy between my thighs; you get the cardio workout you're desperately missing, as well as arm/upper body/back workout, and you don't have to use much legs.  But take care, if your knees are very inflamed and feeling super uncomfortable to the point of pain during this exercise, you shouldn't be doing it.  Stick to the jog belts, floating and gentle walking/cycling motion like those nice old ladies with replacement hip/knees in the deep end for now.

Pull bouy.  Stick it in between your thighs.  Much softer and more therapeutic than men.

photo from SwimOutlet.com

3.  Take painkillers if you're not already.  If the maximum over-the-counter dosages (800mg ibuprofen or 400mg Naproxen) are not even doing anything, see an orthopedic doctor about getting something stronger temporarily to get you going.

4.  Make an appointment to see a licensed Physical Therapist or a bodyworker.  If you can afford to see an Orthopedic/Sports medicine specialist doctor, great.  But don't expect them to fix you, they'll just refer you to a Physical Therapist.  They can only make diagnosis, and sometimes not a great one at that either in our cases.  They are usually doing surgeries on athletes and old people, and have no idea why us young, pretty, healthy looking things are walking in with joint pain.

Have the Physical Therapist or Bodyworker do an assessment of what's going on with your overall body structure right now.  Is your pelvis tilting or twisting one way?  Are your back/ab muscles strong enough to hold you up without stressing hip/knee joints?  Are your IT band/ quad muscles tight and pulling the kneecap?  Are the tendons tight and/or inflamed?  Chances are, your knee cartilage is inflamed as well.  Tell them where it hurts the most and ask them how to start treating it at their office and at home everyday.  Start doing the exercises they give you (probably lots of stretches, a few leg raises, and some massages) every morning and night.

Even if you used to have good posture, chances are, your pain have altered your posture and it's important to get yourself checked out.

5.  Limit the impact and stress on your joints.
Assess how much on-ground walking, standing, sitting (even in bed), and driving you are doing and eliminate them as much as possible.  No running or jogging either.  Find a way to cheat around having to walk for errands:  get your food/groceries delivered, post mails online and have your mailman pick them up, ask friends for help with cooking or dishes.  I ride my bicycle rather than walk to get unavoidable errands done, since cycling is much easier on my joints than walking.  I also ask my friends for rides or call a taxi, since driving puts way more stress on my joints than just lounging in the passenger seat.

Get yourself a well-structured, cushy and lightweight shoes with thick midsoles (like Merrell), box away any medium-high heels and flimsy thin sandals for now.  Get plush carpet or cushy mat for your apartment where you walk around the most.  Super thick, closed-cell foam athletic pads are great for bathroom, kitchen sink, by the bed, and at your work place.

When even laying down on a bed hurts your knees, best option is a good recliner (or a deck lounger) that can give you a very gentle curve at the knee AND hip.  (wide angle at the hip helps prevent tight Psoas muscles, a common problem from sitting for prolonged period of time that leads to hip joint pain)  
Bunch of pillows under the knees and back can do the trick in a pinch, but be warned that any kind of sitting position on the mattress will put stress on your Psoas muscles.  

AAAAAAAAAAAAAHHH.....

If you have a desk job, find a way to make it a standing/perching(lightly leaning on a high stool)/sitting combination work station.  Again, we're trying to avoid your psoas muscles from being contracted all the time, as well as to avoid prolonged sitting/staying in the same posture.  Take a break every 5 minutes to stretch gently for a minute or two, and change work station from sitting-perching-standing-lounging (if possible) from time to time.

Of course, most of us HAVE to work on the chair for the most of the time. (Me included)  Research good posture habits and invest in a good chair/balance ball/saddle chair/stool/whatever that works for you.

 

Angles to keep in mind - neck/back, at the hip, and at the knees.  Try to get the straightest line (widest angle) possible.

                                                  Photo from CoreAwareness.com

6.  Book a massage.  Get it regularly- weekly or biweekly at least.  Your muscles, tendons, and all the connective tissues are probably getting very tight and knotted (or sensitive) from trying to compensate for your knee pain.  If this continues, you'll get fibromyalgia and life becomes even more painful.  Make sure to tell the massage therapist about your joint problems and ask for a gentle, therapeutic direct and indirect myofascial release.  I also highly recommend Reflexology (very therapeutic and the whole body feels better) and Shiatsu/Thai massage.
If you're on a budget, find a massage therapy school nearby and look for a student clinic, where you can get massages from training students for much less money.

7.  In between massages/therapies, do gentle stretches and self myofascial release (self-massage) every day.  Learn to use foam roller (softer is better since you're probably very tight all-over from the pain) or self-massage balls.  I found good relief from Yamuna Body Rolling and MELT method; 

I have this MELT roller which I like, it's much much softer and cushier than the usual foam rollers.

I do one or both forms of self massage everyday, and in addition massage my tendons on my knees and hips in a perpendicular angle to the fiber growth (which helps repair tendons better) with my fingers/knuckles using an anti-inflammatory creams as a lubricant.

8.  Look for any kind of low impact exercise you can do regularly like yoga, pilates, cycling, rock climbing/bouldering, brisk walking on mulch, swimming (you're already doing that, right?), etc.
For example, I used to enjoy hiking, jogging and kendo, all of which used a lot of knees.  I have since then started swimming again, and learned cross-country skiing, rock climbing/bouldering, and aerial silk.  For walks, trekking poles will help immensely.

Hiking/Trekking Poles.  Get a pair and learn to use them, they'll become your best friends.

Also look for feel-good hobbies that you can enjoy without involving the use of knees/sitting.  If you have no hobbies that doesn't involve knees, start learning new ones.  I started listening to audio books while doing the stretches/self-massages/exercises, and I watched a lot of feel-good movies/TV series while I spent a lot of time lounging/laying down.  (actual books and laptops are tricky to hold up for a long period of time while laying down)  A television should be the biggest you can afford and be positioned just right height/angle to avoid neck strain.  
A friend of mine also suggests taking up knitting/cross stitching.
We want the activities to give you enough exercise and/or endorphin boost, to help with your mood, and heal/strengthen the body.

9.  Start having serious conversations with friends, work colleagues/bosses and families about your joint problems.  Don't just say "Owww my knees are still sore, this sucks!", instead, tell them "I'm very concerned about how dysfunctional my knee joints have become, and I'm going to see someone about it.  It's depressing me to have joint problems at my age, and I could really use some support."
Ask for all the help you can get.  Monetary, physical, psychological.  Don't let the problem get bigger than they already are, get serious and admit you have a serious problem.  And get ready to start treating yourself NOW.

10.  Start coming up with a game plan for a new change of lifestyle - it'll require lots of research, and you'll have to change the plans many times depending on how you respond to it.  Build a day-to-day routine and strive for consistency, so you can better monitor your response and progress.  I'll have posts dedicated to this "Planning" part, check them out and aim to make your own personalized game plan best suited for you.