The knee is a complex joint made up of different structures including bones, tendons, ligaments and muscles. They all work together to maintain 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.
The Knee is a hinge joint made up of two bones, the thigh bone (femur) and the shinbone (tibia). There are two round knobs at the end of the femur called femoral condyles which articulate with the flat surface of the tibia called the tibial plateau. The tibia plateau on the inside of the leg is called the medial tibial plateau, and on the outside of the leg it is called 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 knee cap. 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 form 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 & Menisci
Movement of the bones causes friction between the articulating surfaces. To reduce this friction, all articulating surfaces involved in 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 which 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 there 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 by preventing 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 are tough bands of tissue that connect one bone to another bone. The ligaments of the knee function to stabilize the knee joint. There are two important groups of ligaments that hold the bones of the knee joint together, collateral ligaments and the cruciate ligament.
Collateral ligaments are present on either side of the knee. They function to 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 - This group of 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 or ACL and the cruciate ligament in the back of the knee is called posterior cruciate ligament or PCL.
Muscles: There are two major muscles, the quadriceps and the hamstrings, which enable movement of the knee joint. The quadriceps muscles are in the front of the thigh. When the quadriceps muscles contract, the knee straightens. The hamstrings are in the back of the thigh. When the hamstring muscles contract, the knee bends.
Tendons are structures that attach muscles to the 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.
Arthritis is a general term covering numerous conditions where the joint surface or cartilage wears out. The joint surface is covered by a smooth articular surface that allows pain free movement in the joint. This surface can wear out for several reasons; often the definite cause is not known.
The knee is one of the largest joints in the body, formed by the lower end of the femur, upper end of the tibia and the patella or knee cap. Several ligaments and muscles attach to the bones of the knee joint to maintain normal motion of the joint. Special cartilaginous tissues known as menisci are placed between the two articular ends of the joint. These act as a cushion between the articular surfaces and absorb the shock during movement
Runner's knee, also called patellofemoral pain syndrome refers to pain under and around your kneecap. Runner’s knee includes several medical conditions such as anterior knee pain syndrome, patellofemoral malalignment, and chondromalacia patella that cause pain around the front of the knee. As the name suggests, runner’s knee is a common complaint among runners, jumpers, and other athletes such as skiers, cyclists, and soccer players.
Osteochondritis dissecans is a joint condition in which a piece of cartilage, along with a thin layer of the bone separates from the end of the bone because of inadequate blood supply. The separated fragments are sometimes called “joint mice”. These fragments may be localised, or may detach and fall into the joint space causing pain and joint instability.
The anterior cruciate ligament, or ACL, is one of the major ligaments of the knee that is in the middle of the knee and runs from the femur (thigh bone) to the tibia (shin bone). It prevents the tibia from sliding out in front of the femur. Together with posterior cruciate ligament (PCL) it provides rotational stability to the knee.
The knee is a complex joint of the body which is vital for movement. The four major ligaments of the knee are anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament. They play an important role in maintaining the stability of the knee. An injury resulting in tear of one or more ligaments of the knee thus affects knee stability.
The knee can be divided into three compartments: patellofemoral, medial and lateral compartment. The patellofemoral compartment is the compartment in the front of the knee between the knee cap and thigh bone. The medial compartment is the area on the inside portion of the knee, and the lateral compartment is the area on the outside portion of the knee joint.
Meniscus tear is the commonest knee injury in athletes, especially those involved in contact sports. A suddenly bend or twist in your knee cause the meniscus to tear. This is a traumatic meniscus tear. Elderly people are more prone to degenerative meniscal tears as the cartilage wears out and weakens with age. The two wedge-shape cartilage pieces’ present between the thighbone and the shinbone are called meniscus. They stabilize the knee joint and act as “shock absorbers”.
Osteonecrosis is a condition in which death of a section of bone occurs because of lack of blood supply to it. It is one of the most common causes of knee pain in older women. Women over the age of 60 years of age are commonly affected, three times more often than men.
Knee Arthroscopy is a common surgical procedure performed using an arthroscope, a viewing instrument, to consider the knee joint to diagnose or treat a knee problem. It is a relatively safe procedure and most the patient’s discharge from the hospital on the same day of surgery.
Arthroscopic ACL Reconstruction
The anterior cruciate ligament is one of the major stabilizing ligaments in the knee. It is a strong rope like structure located in the centre of the knee running from the femur to the tibia. When this ligament tears unfortunately, it does not heal and often leads to the feeling of instability in the knee.
The knee can be divided into three compartments: patellofemoral, medial and lateral compartment. The patellofemoral compartment is the compartment in the front of the knee between the knee cap and thigh bone. The medial compartment is the area on the inside portion of the knee, and the lateral compartment is the area on the outside portion of the knee joint. Patellofemoral instability means that the patella (kneecap) moves out of its normal pattern of alignment.
High tibial osteotomy is a surgical procedure performed to relieve pressure on the damaged site of an arthritic knee joint. It is usually performed in arthritic conditions affecting only one side of your knee and the aim is to take pressure off the damaged area and shift it to the other side of your knee with healthy cartilage. During the surgery, your surgeon will remove or add a wedge of bone either below or above the knee joint depending on the site of arthritic damage.
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. The knee can be divided into three compartments: patellofemoral, the compartment in front of the knee between the knee cap and thigh bone, medial compartment, on the inside portion of the knee, and lateral compartment which is the area on the outside portion of the knee joint.
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 artificial parts. The knee is made up of the femur (thigh bone), the tibia (shin bone), and patella (kneecap). The meniscus, the soft cartilage between the femur and tibia, serves as a cushion and helps absorb shock during motion.