The knee is a very complicated joint, involving four bones, femur (upper leg), tibia and fibula (lower leg bones), and patella (knee cap), numerous ligaments which connect the bones to one another, and two meniscus, which are firm pieces of connective tissue which serve as shock absorbers. Like all joints there are multiple bursa (small pockets of fluid) surrounding the joint, and numberous tendons which connect the muscles to the bones. Damage to any of these structures can cause problems. It is difficult to be know what is wrong with your knee without examining it. You should probably see a doctor for evaluation and treatment. Sorry, I can't tell you more.