Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Catherine Burt Driver, MD, is board certified in internal medicine and rheumatology by the American Board of Internal Medicine. Dr. Driver is a member of the American College of Rheumatology. She currently is in active practice in the field of rheumatology in Mission Viejo, Calif., where she is a partner in Mission Internal Medical Group.
The knee joint has three compartments: medial, lateral, and patellofemoral.
Causes of knee pain include injury, degeneration,
arthritis, infrequently infection, and rarely bone tumors.
Ligaments within the knee (cruciate ligaments) and on
the inner and outer sides of the knee (collateral ligaments) stabilize the
Surgical repair of ligament injury can involve
suturing, grafting, and synthetic graft repair. Some patients require total knee replacement.
Routine X-rays do not reveal meniscus tears but can
be used to exclude other problems of the bones and other tissues. Arthroscopy and MRI studies are used most frequently to diagnose knee ailments; occasionally, a needle aspiration of fluid is done.
The knee joint is one of the most commonly involved joints in rheumatic diseases (over 100 disease types). Rheumatic diseases are immune diseases that affect various tissues of the body, including the joints, by causing arthritis (pain, swelling, stiffness, and limited joint movements).
How is the knee designed, and what is its function?
The knee is a joint that has three compartments. 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 thighbone (femur) meets the large shinbone (tibia), forming the main knee 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
Picture of the knee joint
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.
The goal of this article is to give the reader an overview of causes of knee pain. Most of the topics covered in this article are further expanded in detail as separate articles. For example,
bursitis, types of arthritis, total knee replacement, and others are covered in articles devoted to knee pain-related topics that include specifics on diagnosis, tests, treatments,
and other details.
Reviewed by Catherine Burt Driver, MD on 11/16/2011
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 cartilagebeneath 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
Chondromalacia commonly occurs in females. Girls in their teensare 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.