The term "knee problem" refers to any issue or condition that affects a person's knees, which are essential for walking, running and other physical activities. Knee problems can be caused by injuries, overuse, aging, obesity, poor posture or structural abnormalities such as arthritis, patellofemoral pain syndrome, chondromalacia, tendonitis, bursitis, and ligament sprains. Symptoms may include pain, swelling, stiffness, instability, locking or popping sensations in the knee joint. Treatment options for knee problems can vary from rest, physical therapy to medication, cortisone shots, or surgery depending on the severity and cause of the condition.