Knee Pain

Medical Author: William C. Shiel Jr., MD, FACP, FACR
Medical Editor: Dennis Lee, MD

• How is the knee designed, and what is its function?
• What injuries can cause knee pain, and what other symptoms may accompany knee pain?
• What are diseases and conditions that can cause knee pain, and how are they treated?
• Knee Pain At A Glance
• Patient Discussions: Knee Pain - Length Symptoms Lasted

Your Knee Pain: Is It Chondromalacia? Medical Author: Melissa Conrad Stöppler, MD Medical Editor: Barbara K. Hecht, PhD Chondromalacia, technically termed chondromalacia patellae, is the most common cause of chronic knee pain. The condition is also called the patellofemoral syndrome. Softening of the cartilage beneath the knee cap (the patella) results in small areas of breakdown and pain around the knee. Instead of gliding smoothly over the knee, the knee cap rubs against the thigh bone (the femur) when the knee moves. The changes can range from mild to complete erosion of the cartilage. Chondromalacia commonly occurs in females. Girls in their teens are at elevated risk because the cartilage of the knee is subjected to excessive and uneven pressure due to the structural changes that accompany rapid growth. Learn about treatments for knee pain » Top Searched Knee Pain Terms: causes, inner knee pain, osteoarthritis, treatment, injuries, arthritis

How is the knee designed, and what is its function?

The knee is a joint that has three compartments. The thigh bone (femur) meets the large shin bone (tibia) forming the main knee joint. This joint has an inner (medial) and an outer (lateral) compartment. The kneecap (patella) joins the femur to form a third compartment, called the patellofemoral joint.

The knee joint is surrounded by a joint capsule with ligaments strapping the inside and outside of the joint (collateral ligaments) as well as crossing within the joint (cruciate ligaments). These ligaments provide stability and strength to the knee joint.

The meniscus is a thickened cartilage pad between the two joints formed by the femur and tibia. The meniscus acts as a smooth surface for motion and absorbs the load of the body above the knee when standing. The knee joint is surrounded by fluid-filled sacs called bursae, which serve as gliding surfaces that reduce friction of the tendons. Below the kneecap, there is a large tendon (patellar tendon) which attaches to the front of the tibia bone. There are large blood vessels passing through the area behind the knee (referred to as the popliteal space). The large muscles of the thigh move the knee. In the front of the thigh, the quadriceps muscles extend the knee joint. In the back of the thigh, the hamstring muscles flex the knee. The knee also rotates slightly under guidance of specific muscles of the thigh.

The knee functions to allow movement of the leg and is critical to normal walking. The knee flexes normally to a maximum of 135 degrees and extends to 0 degrees. The bursae, or fluid-filled sacs, serve as gliding surfaces for the tendons to reduce the force of friction as these tendons move. The knee is a weight-bearing joint. Each meniscus serves to evenly load the surface during weight-bearing and also aids in disbursing joint fluid for joint lubrication.

Knee Pain - Length Symptoms Lasted

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