My knees hurt when it rains and gets cold, and at times I can't bend them, they also crack really loud what should I do? I banged my knees of sidewalk when I was 2, I've also had fluid in the knees constantly, I tore a muscle in my leg about 4 years ago,

SEE KNEE SPECIALIST. Knee pain is common. Stiffness, cracking and locking may mean that you have a cartilage injury in your knee. A thorough evaluation including xrays and mris, and perhaps blood tests is indicated. See you local knee doc.
The . The injury you had at age two is unlikely to be causing your symptoms now. It is also unlikely you had arthritis at age 12, unless you had a condition called jra. If you truly have fluid in your knees, then you should see a rheumatologist or an orthopaedic surgeon. Pain with weather changes is common in people with arthritis. Cracking in the knees is usually not serious.