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.
An iliotibial band is a tough group of fibers that runs from the iliac crest of the hip along the outside of the thigh, till the outer side of the shinbone, just below the knee joint. Its function is to coordinate with the thigh muscles and provide stability to the knee joint.
Shin splints are pain and inflammation of the tendons, muscles and bone tissue along the tibia or shinbone (lower leg). It occurs because of vigorous physical activities such as exercise or sports. The condition is also referred to as medial tibial stress syndrome (MTSS).
Knee infection is a serious medical condition that needs immediate treatment. Infection may occur followed by a knee replacement surgery or trauma and is usually caused by bacteria. Infection may spread to the space of the knee joint or deep layers of your knee causing serious complications.
The anterior cruciate ligament (ACL) is one of the major ligaments of the knee. It is located in the middle of the knee and runs from the femur (thighbone) to the tibia (shinbone). The ACL prevents the tibia from sliding out in front of the femur. Together with the posterior cruciate ligament (PCL), it provides rotational stability to the knee.
Meniscal tears are among the commonest injuries to the knee joint. It can occur at any age but are more common in athletes involved in contact sports. The meniscus has no direct blood supply and for that reason, when there is an injury to the meniscus, healing is difficult.
A meniscal tear is a common knee injury in athletes, especially those involved in contact sports. A sudden bend or twist in your knee causes the meniscus to tear. Elderly people are more prone to degenerative meniscal tears as the cartilage wears out and weakens with age.
The knee is a complex joint of the body that is vital for movement. The four major ligaments of the knee are anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL) and lateral collateral ligament (LCL). They play an important role in maintaining the stability of the knee.
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. When the articular cartilage wears out, the bone ends rub on one another and cause pain.
Patellar dislocation occurs when the patella moves out of the patellofemoral groove, (trochlea) onto the bony head of the femur. If the kneecap partially comes out of the groove, it is called subluxation; if the kneecap completely comes out, it is called dislocation (luxation).
The 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 your 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.
The kneecap or patella forms a part of the knee joint. It is present at the front of the knee, protecting the knee and providing attachment to various muscle groups of the thigh and leg. The undersurface of the kneecap and the lower end of the femur are coated with articular cartilage, which helps in smooth movement of the knee joint.
The patella (kneecap) is a small bone that shields your knee joint. It is present in front of your knee, on a groove called the trochlear groove that sits at the junction of the femur (thighbone) and tibia (shinbone). Articular cartilage presents below the patella and end of the femur cushion and helps the bones glide smoothly over each other when the legs move.
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.
Trauma is any injury caused during physical activity, motor vehicle accidents, electric shock, or other activities. Sports trauma or sports injuries refer to injuries caused while playing indoor or outdoor sports and exercising. Sports trauma can result from accidents, inadequate training, improper use of protective devices, or insufficient stretching or warm-up exercises.
Of the menisci within the knee, it is the medial that is more easily injured. Differences in the anatomical attachments of the medial meniscus compared to the lateral, mean that the medial meniscus becomes distorted during combined flexion and rotation movements in a manner not experienced on the lateral side.
Knee pain is a common condition affecting individuals of different age groups. It not only affects movement but also impacts your quality of life. An injury or disease of the knee joint or any structure surrounding the knee can result in knee pain. A precise diagnosis of the underlying cause is important to develop an appropriate treatment plan.
Anterior knee pain is characterized by chronic pain over the front and center of the knee joint. It is common in athletes, active adolescents (especially girls) and overweight individuals. Anterior knee pain refers to various conditions, which include runner's knee or patellar tendinitis, and chondromalacia of the patella.
Osgood-Schlatter disease refers to an overuse injury that occurs in the knee of growing children and adolescents. This is caused by inflammation of the tendon located below the kneecap (patellar tendon). Children and adolescents who participate in sports such as soccer, gymnastics, basketball, and distance running are at a higher risk of this disease.
Partial arthroscopic meniscectomy is a procedure to remove the damaged part of a meniscus in the knee joint with the help an arthroscope. The meniscus is a C-shaped disc of cartilage between your thighbone and shinbone. There are 2 menisci in each knee. They act as shock absorbers and provide stability to the joint.
Arthroscopic debridement or a clean-up is a surgical procedure performed using an arthroscope. In this procedure, the cartilage or the bone that is damaged is removed using surgical instruments and the edges of the articular cartilage that are rough will be smoothened. A washout or joint lavage is done using a special tool to spray jets of fluid to wash and suck out to remove the remaining debris around the joint.
Meniscectomy is a surgical procedure indicated in individuals with torn meniscus where the conservative treatments are a failure to relieve the pain and other symptoms. Meniscectomy is recommended based on the ability of meniscus to heal, patient’s age, health status, and activity level.
Physeal sparing reconstruction of the anterior cruciate ligament is a surgery to replace a torn anterior cruciate ligament or ACL, a major ligament of the knee, while minimizing damage to the growth plate (physis) present near the end of the bone.
Physical therapy is an exercise program that helps you to improve movement, relieve pain, encourage blood flow for faster healing, and restore your physical function and fitness level. It can be prescribed as an individual treatment program or combined with other treatments.
The medial patellofemoral ligament is a band of tissue that extends from the femoral medial epicondyle to the superior aspect of the patella. It is a major ligament that stabilizes the patella and helps in preventing patellar subluxation (partial dislocation) or dislocation.
The anterior cruciate ligament is one of the four major ligaments of the knee that connects the femur (thighbone) to the tibia (shinbone) and helps stabilize the knee joint. The anterior cruciate ligament prevents excessive forward movement of the lower leg bone (tibia) in relation to the thighbone (femur) as well as limits rotational movements of the knee.
The anterior cruciate ligament (ACL) is one of the major stabilizing ligaments in the knee. It is a strong rope-like structure located in the center of the knee running from the femur to the tibia. When this ligament tears, it does not heal on its own and often leads to the feeling of instability in the knee.
Two wedge-shaped cartilage pieces are present between the thighbone and the shinbone. These are called menisci. They stabilize the knee joint and act as shock absorbers. Partial meniscectomy is a surgical procedure to remove the torn portion of the meniscus from the knee joint.
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. The elderly are more prone to degenerative meniscal tears as the cartilage wears out and weakens with age.
The knee is a complex joint which consists of bone, cartilage, ligaments, and tendons that make joint movements easy and at the same time it is more susceptible to various kinds of injuries. Knee problems may arise if any of these structures get injured by overuse or suddenly during sports activities.