Here are some common causes of knee pain:

• Arthritis of the Knee – Osteoarthritis is the most common form of arthritis in the knee and is caused by gradual degradation of the cartilage in the joint. Rheumatoid arthritis results in inflammation of the joint and destroy surrounding cartilage. While deformity can lead to arthritis in the knee, it is more often the result of excesses weight or repetitive stress injuries (such as sports injuries). Stiffness and/or locking joints are common symptoms.
• Cartilage injuries – Cartilage injuries occur most often in runners, cyclists, skiers, and soccer players. Chondromalacia patella, which is a softening of the kneecap cartilage, is a common cartilage injury.
• Illobtibial band syndrome – Often caused by stress of the tendon from longterm overuse, Illobtibial band syndrome results in inflammation of a tendon after having been rubbed over the outer knee repeatedly. This pain can also radiate and move up the thigh.
• Ligament injuries – A large amount of pain can be felt when the anterior cruciate ligament (ACL) and posterior cruciate ligament become sprained. Sudden twisting motions can stretch or tear the ACL. Direct impact is what most often causes injury to the PCL (most often the result of sports collisions and automobile accidents). Injury the PCL typically consists of a pop sound followed by buckling of the knees.
• Meniscus injuries – Repetition of quick twists and/or rotations of the knee while under a significant amount of weight can cause meniscus injuries.
• Osgood-Schlater disease – Repetitive stress to the upper tibia or leg bone can cause the condition called Osgood-Schlater disease. Inflammation occurs in the patellar tendon and surrounding soft tissues. This condition is particularly prone to pre-adolescent boys who are involved in frequent athletic activities.
• Tendon injuries – Anything from tendonitis to a tendon getting ruptured or torn can result in knee pain. Overuse and continual stretching of tendons can result in feelings of inflammation.