Osteoarthritis is when the cartilage that protects the knee joint wears over time as you age. The friction can cause joint pain and reduce your mobility.
The most common symptoms of osteoarthritis are joint pain, mobility issues and stiffness in the joint
Rheumatoid arthritis is an inflammatory conditions when immune system attacks your healthy tissue. The tissue becomes inflamed and painful and if left untreated can cause damage to the joint.
Septic arthritis can happen following a wound on your joint which becomes infected. It is less common but if left untreated can be serious.