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Knee Anatomy

The knee is a complex joint made up of different structures - bones, tendons, ligaments, and muscles. They all work together to maintain the knee’s normal function and provide stability to the knee during movement.

Having a well-functioning healthy knee is essential for our mobility and ability to participate in various activities. Understanding the anatomy of the knee enhances your ability to discuss and choose the right treatment procedure for knee problems with your doctor.

Bones of the Knee

The knee is a hinge joint made up of two bones, the thighbone (femur) and shinbone (tibia). There are two round knobs at the end of the femur called femoral condyles that articulate with the flat surface of the tibia called the tibial plateau. The tibial plateau on the inside of the leg is called the medial tibial plateau and on the outside of the leg, the lateral tibial plateau.

The two femoral condyles form a groove on the front (anterior) side of the knee called the patellofemoral groove. A small bone called the patella sits in this groove and forms the kneecap. It acts as a shield and protects the knee joint from direct trauma.

A fourth bone called the fibula is the other bone of the lower leg. This forms a small joint with the tibia. This joint has very little movement and is not considered a part of the main joint of the knee.

Articular Cartilage and Menisci of the Knee

Movement of the bones causes friction between the articulating surfaces. To reduce this friction, all articulating surfaces involved in the movement are covered with a white, shiny, slippery layer called articular cartilage. The articulating surface of the femoral condyles, tibial plateaus and the back of the patella are covered with this cartilage. The cartilage provides a smooth surface that facilitates easy movement.

To further reduce friction between the articulating surfaces of the bones, the knee joint is lined by a synovial membrane that produces a thick clear fluid called synovial fluid. This fluid lubricates and nourishes the cartilage and bones inside the joint capsule.

Within the knee joint, between the femur and tibia, are two C-shaped cartilaginous structures called menisci. Menisci function to provide stability to the knee by spreading the weight of the upper body across the whole surface of the tibial plateau. The menisci help in load-bearing i.e. it prevents the weight from concentrating onto a small area, which could damage the articular cartilage. The menisci also act as a cushion between the femur and tibia by absorbing the shock produced by activities such as walking, running and jumping.

Ligaments of the Knee

Ligaments are tough bands of tissue that connect one bone to another bone. The ligaments of the knee stabilize the knee joint. There are two important groups of ligaments that hold the bones of the knee joint together, collateral and cruciate ligaments.

Collateral ligaments are present on either side of the knee. They prevent the knee from moving too far during side to side motion. The collateral ligament on the inside is called the medial collateral ligament (MCL) and the collateral ligament on the outside is called the lateral collateral ligament (LCL).

Cruciate ligaments, present inside the knee joint, control the back-and-forth motion of the knee. The cruciate ligament in the front of the knee is called anterior cruciate ligament (ACL) and the cruciate ligament in the back of the knee is called posterior cruciate ligament (PCL).

Muscles of the Knee

There are two major muscles in the knee - the quadriceps and the hamstrings, which enable movement of the knee joint. The quadriceps muscles are located in front of the thigh. When the quadriceps muscles contract, the knee straightens. The hamstrings are located at the back of the thigh. When the hamstring muscles contract, the knee bends.

Tendons of the Knee

A tendon is a tissue that attaches a muscle to a bone. The quadriceps muscles of the knee meet just above the patella and attach to it through a tendon called the quadriceps tendon. The patella further attaches to the tibia through a tendon called the patella tendon. The quadriceps muscle, quadriceps tendon, and patellar tendon all work together to straighten the knee. Similarly, the hamstring muscles at the back of the leg are attached to the knee joint with the hamstring tendon.

Knee Conditions

  • Knee Arthritis Knee Arthritis

    The joint surface is covered by a smooth articular surface that allows pain-free movement in the joint. Arthritis is a general term covering numerous conditions where the joint surface or cartilage wears out. This surface can wear out for several reasons; often the definite cause is not known. Arthritis often affects the knee joint.

  • Periprosthetic Knee Fractures Periprosthetic Knee Fractures

    Knee replacement, also called knee arthroplasty, is a surgical procedure in which the worn-out or damaged surfaces of the knee joint are removed and replaced with artificial implants. Any resulting fractures or breaks in the bone around the implant are called periprosthetic knee fractures.

  • Periprosthetic Knee Infections Periprosthetic Knee Infections

    A very small percentage of patients (less than 1%) who undergo knee replacement may develop an infection around the knee joint. This infection is called a periprosthetic knee infection.

    Your immune system is usually able to protect the body from bacteria or other infectious organisms by attacking it through the lymph system or blood stream.

Knee Procedures

  • Total Knee Replacement Total Knee Replacement

    Total knee replacement, also called total knee arthroplasty, is a surgical procedure in which the worn out or damaged surfaces of the knee joint are removed and replaced with an artificial prosthesis.

    The knee is made up of the femur (thighbone), tibia (shinbone) and patella (kneecap). The two menisci, the soft cartilage between the femur and tibia, serve as a cushion and help absorb shock during motion.

  • Unicompartmental/Partial Knee Replacement Unicompartmental/Partial Knee Replacement

    Unicompartmental knee replacement is a minimally invasive surgery in which only the damaged compartment of the knee is replaced with an implant. It is also called a partial knee replacement.

  • Revision Knee Replacement Revision Knee Replacement

    Revision knee replacement surgery involves replacing a part or all your previous knee prosthesis with a new prosthesis. Although total knee replacement surgery is successful, sometimes the procedure can fail due to various reasons and may require a second revision surgery.

  • Unicondylar knee Replacement Unicondylar knee Replacement

    Unicompartmental knee replacement or unicondylar knee replacement is a minimally invasive surgery in which only the damaged compartment of the knee is replaced with an implant. It is also called a partial knee replacement. The knee can be divided into three compartments: patellofemoral, the compartment in front of the knee between the knee cap and thigh bone

  • Partial Medial Knee Replacement Partial Medial Knee Replacement

    Aging and joint conditions such as osteoarthritis cause breakdown of the cartilage of your inner knee leading to pain and inflammation which may not respond to pain medications or non-surgical treatment and may need surgery. Damage to the medial side of your knee may also cause knee stiffness requiring surgery.

  • Minimally Invasive Knee Joint Replacement Minimally Invasive Knee Joint Replacement

    Total knee replacement is a very successful surgical treatment for knee arthritis. Over the years, minimally invasive knee replacement surgical techniques have been developed to lessen tissue trauma and improve patient outcomes.

  • Tricompartmental Knee Replacement Tricompartmental Knee Replacement

    Arthritis (inflammation of the joints), injury, or other diseases of the joint can damage the protective layer of cartilage, causing extreme pain and difficulty in performing daily activities. Osteoarthritis is the most common form of knee arthritis in which the joint cartilage gradually wears away. It often affects the elderly.

  • Outpatient Total Knee Replacement Outpatient Total Knee Replacement

    Total knee replacement is the surgical treatment for knee arthritis, where the damaged knee is removed and replaced with an artificial knee implant. Traditionally performed as an inpatient procedure, total knee replacement surgery is now being conducted on an outpatient basis, allowing you to go home on the same day of the surgery.

  • Outpatient Unicondylar Knee Replacement Outpatient Unicondylar Knee Replacement

    A unicondylar knee replacement, also known as unicompartmental or partial knee replacement, is a procedure to replace a portion of the damaged knee joint with a prosthetic implant to relieve pain and improve function of the knee joint.

  • Correction of a Loose Knee Replacement Correction of a Loose Knee Replacement

    Knee replacement is a surgery employed to resurface a knee joint damaged by arthritis, wear and tear, or injury and replacing the damaged joint with a prosthesis (an artificial knee joint) to resolve a painful knee condition and loss of motion.

  • Correction of a Painful Knee Replacement Correction of a Painful Knee Replacement

    Reoperation of a total knee replacement to resolve a painful knee condition and loss of motion arising out of a damaged or worn out prosthesis is known as correction of a painful knee replacement. This procedure involves a complete or partial exchange of prostheses implanted during the original total knee replacement with new prostheses.

  • What is New in Knee Replacement What is New in Knee Replacement

    If you are considering knee replacement surgery, there are new developments under study which can help enhance the quality of life

  • Robotic Assisted Knee Replacement Robotic Assisted Knee Replacement

    Robotic-assisted knee replacement surgery is an alternative to the conventional knee replacement procedure. It is performed using robotic-arm technology that allows your surgeon to precisely perform the surgery through a smaller incision as compared to traditional surgery.

Others

  • Pre-op and Post-op Knee Guidelines Pre-op and Post-op Knee Guidelines

    Knee replacement is a surgery performed to replace parts of a diseased knee joint with an artificial prosthesis. The goal of knee replacement is to eliminate pain and return you to your normal activities.

  • Am- I a Candidate for Knee Surgery? Am I a Candidate for Knee Surgery?

    Arthritis of the knee can cause pain and stiffness, making regular activities such as walking and bending difficult. As arthritis progresses, conservative treatments tend to lose their efficacy and more definitive treatment should be considered.

  • After Knee Replacement After Knee Replacement

    Knee replacement is a surgery performed to replace parts of a diseased knee joint with artificial prostheses. The goal of knee replacement is to eliminate pain and return you to your normal activities. You can help in recovery and improve the outcomes of the procedure by following certain precautions and changing the way you carry out your daily activities.

  • American Academy of Orthopaedic Surgeons
  • New England Orthopedic Society
  • aahks
  • Massachusetts General Hospital
  • tufts school of medicine