Knee
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Knee Anatomy
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.
Bones of the Knee
The knee is a hinge joint made up of two bones, the thighbone (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 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 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 of the Knee
Ligaments are tough bands of tissue that connect one bone to another bone. The ligaments of the knee function to stabilise 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, 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 of the Knee
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 of the Knee
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.
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Knee Pain
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 kneecap. 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.
Knee Arthritis
Osteoarthritis, also called degenerative joint disease, is the most common form of arthritis. It occurs most often in older people. This disease affects the tissue covering the ends of bones in a joint (cartilage). In a person with osteoarthritis, the cartilage becomes damaged and worn out causing pain, swelling, stiffness and restricted movement in the affected joint. Although osteoarthritis may affect various joints including hips, knees, hands, and spine, hip joint is most commonly affected. Rarely, the disease may affect the shoulders, wrists and feet.
Chondral (Articular Cartilage Defects)
Articular or hyaline cartilage is the tissue lining the surface of the two bones in the knee joint. Cartilage helps the bones move smoothly against each other and can withstand the weight of the body during activities such as running and jumping. Articular cartilage does not have a direct blood supply to it, so has less capacity to repair itself. Once the cartilage is torn it will not heal easily and can lead to degeneration of the articular surface, leading to development of osteoarthritis.
Ligament Injuries
The knee is a complex joint which consists of bone, cartilage, ligaments and tendons that make joint movements easy and at the same time more susceptible to various kinds of injuries.
ACL Tears
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 (thighbone) to the tibia (shinbone). 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.
MCL Tears
The medial collateral ligament (MCL) is the ligament that is located on the inner part of the knee joint. It runs from the femur (thighbone) to the top of the tibia (shinbone) and helps in stabilising the knee.
PCL Injuries
Posterior cruciate ligament (PCL), one of four major ligaments of the knee, is situated at the back of the knee. It connects the thighbone (femur) to the shinbone (tibia). The PCL limits the backward motion of the shinbone.
Meniscal Tears
Meniscus tear is the commonest knee injury in athletes, especially those involved in contact sports. A sudden bend or twist in your knee causes 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-shaped cartilage pieces present between the thighbone and the shinbone are called meniscus. They stabilise the knee joint and act as “shock absorbers”.
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Non-surgical Treatments
Viscosupplementation
Viscosupplementation refers to the injection of a hyaluronan preparation into the joint. Hyaluronan is a natural substance present in the joint fluid that assists in lubrication. It allows smooth movement of the cartilage covered articulating surfaces of the joint.
Cortisone Injection
Cortisone is a corticosteroid released by the adrenal gland in response to stress and is a potent anti-inflammatory agent.
Surgical Treatment
Knee Arthroscopy
The knee joint is one of the most complex joints of the body. The lower end of the thighbone (femur) meets the upper end of the shinbone (tibia) at the knee joint. A small bone called the patella (kneecap) rests on a groove on the front side of the femoral end. A bone of the lower leg (fibula) forms a joint with the shinbone.
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 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. Arthritis (inflammation of the joints), injury, or other diseases of the joint can damage this protective layer of cartilage, causing extreme pain and difficulty in performing daily activities. Your doctor may recommend surgery if non-surgical treatment options have failed to relieve the symptoms.
Unicompartmental Knee Replacement
Arthritis is inflammation of a joint causing pain, swelling (inflammation), and stiffness. Osteoarthritis is the most common form of knee arthritis in which the joint cartilage gradually wears away. It most often affects older people. In a normal joint, articular cartilage allows for smooth movement within the joint, where as in an arthritic knee the cartilage itself becomes thinner or completely absent. In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. These factors can cause pain and restricted range of motion in the joint.
Revision Knee Replacement
Revision knee replacement surgery involves replacing 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.
Arthroscopic Reconstruction of the Knee for Ligament Injuries
The knee is the most complex joint in the body and is formed by the articulation between the thighbone (femur) and the shinbone (tibia). A kneecap is present over the front of the joint to provide extra protection. These bones are held together by four strong rope- like structures called ligaments. Two collateral ligaments are present on either side of the knee and control the sideway movements of the knee. The other two ligaments are the anterior and posterior cruciate ligaments, ACL and PCL respectively, which are present in the centre of the knee joint and cross each other to form an “X”. The cruciate ligaments control the back and forth movement of the knee.
ACL Reconstruction
The anterior cruciate ligament is one of the major stabilising 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.
Medial Patellofemoral Ligament Reconstruction
Medial patellofemoral ligament reconstruction is a surgical procedure indicated in patients with more severe patellar instability. Medial patellofemoral ligament is a band of tissue that extends from the femoral medial epicondyle to the superior aspect of the patella. Medial patellofemoral ligament is the major ligament which stabilises the patella and helps in preventing patellar subluxation (partial dislocation) or dislocation. This ligament can rupture or get damaged when there is patellar lateral dislocation. Dislocation can be caused by a direct blow to the knee, twisting injury to the lower leg, strong muscle contraction, or because of a congenital abnormality such as shallow or malformed joint surfaces.
PCL Reconstruction
Posterior cruciate ligament (PCL), one of four major ligaments of the knee is situated at the back of the knee. It connects the thighbone (femur) to the shinbone (tibia). The PCL limits the backward motion of the shinbone.
Meniscal Surgery
A meniscus tear is the commonest knee injury in athletes, especially those involved in contact sports. A sudden bend or twist in your knee can cause the meniscus to tear. This is a traumatic meniscal tear. Elderly people are more prone to degenerative meniscal tears as the cartilage wears out and weakens with age.
