Knee Pain

Take the Pain Quiz

Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

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.

View Full Profile

Medical Editor:

Jerry R. Balentine, DO, FACEP

Jerry R. Balentine, DO, FACEP

Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

View Full Profile

• Knee Pain Introduction
• Anatomy of the Knee
• Home Care for Knee Pain
• When to Call the Doctor About Knee Pain
• When to Go to the Hospital for Knee Pain
• Knee Pain Diagnosis
• Causes, Symptoms, Signs, Treatment, Prognosis, and Types of Knee Pain
• Prevention of Knee Pain
• Synonyms and Keywords
• Authors and Editors
• Take the Pain Quiz
• Viewer Comments: Knee Pain - Causes
• Viewer Comments: Knee Pain - Length Symptoms Lasted

Knee Pain Introduction

Knee pain is one of the most common musculoskeletal complaint that brings people to their doctor. With today's increasingly active society, the number of knee problems is increasing. Knee pain has a wide variety of specific causes and treatments.

Anatomy of the Knee

The knee joint's main function is to bend and straighten. The knee, more than just a simple hinge, however, also twists and rotates. In order to perform all of these actions and to support the entire body while doing so, the knee relies on a number of structures, including bones, ligaments, tendons, and cartilage.

• Bones



• The knee joint involves three bones.



• The thighbone or femur comprises the top portion of the joint.



• One of the bones in the lower leg (or calf area), the tibia, provides the bottom portion of the joint.



• The kneecap or patella rides along the front of the femur.



• The remaining bone in the calf, the fibula, is not involved in the knee joint but is close to the outer portion of the joint.



• Ligaments



• Ligaments are fibrous bands that connect bones to each other.



• The knee includes four important ligaments, all four of which connect the femur to the tibia:



• The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) provide front and back (anterior and posterior) and rotational stability to the knee.



• The medial collateral ligament (MCL) and lateral collateral ligament (LCL) located along the inner (medial) and outer (lateral) sides of the knee provide medial and lateral stability to the knee.




• Tendons



• Tendons are fibrous bands similar to ligaments.



• Instead of connecting bones to other bones as ligaments do, tendons connect muscles to bones.



• The two important tendons in the knee are (1) the quadriceps tendon connecting the quadriceps muscle, which lies on the front of the thigh, to the patella and (2) the patellar tendon connecting the patella to the tibia (technically this is a ligament because it connects two bones).



• The quadriceps and patellar tendons as well as the patella itself are sometimes called the extensor mechanism, and together with the quadriceps muscle they facilitate leg extension (straightening).



• Cartilage



• Cartilaginous structures called menisci (one is a meniscus) line the top of the tibia and lie between the tibia and the two knuckles at the bottom of the femur (called the femoral condyles).



• Menisci provide both space and cushion for the knee joint.



• Bursae



• Bursae (one is a bursa) are fluid-filled sacs that help to cushion the knee. The knee contains three important groups of bursae.



• The prepatellar bursae lie in front of the patella.



• The anserine bursae are located on the inner side of the knee about 2 inches below the joint.



• The infrapatellar bursae are located underneath the patella.