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.
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.
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).
A bursa is a small fluid-filled sac found between soft tissues and bones. It lubricates and acts as a cushion, decreasing the friction between bones when they move. Bursitis refers to the inflammation and swelling of the bursa. Goosefoot bursitis or pes anserine bursitis is the inflammation of the bursa present between the tendons of the hamstring muscle and the tibia (shinbone) on the inner side of the knee.
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 patella or kneecap is a small bone present in the front of your knee where the thigh bone meets the shinbone. It provides protection to your knee and attachment to muscles in the front of the thigh. An injury to the knee can result in a break or fracture of the patella.
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. A fracture in the kneecap is rare but common in adult males.
The knee joint is formed by the union of two bones, namely the femur (thighbone) and the tibia (lower leg bone). At the junction of these two bones is a cartilage called meniscus, which acts as a shock absorber. There are two menisci – the lateral and medial menisci. The lateral meniscus is the outer meniscus of the knee joint and gives a cushioning effect during weight-bearing activities
An osteochondral defect, also commonly known as osteochondritis dissecans, of the knee refers to a damage or injury to the smooth articular cartilage surrounding the knee joint and the bone underneath the cartilage. The degree of damage may range from a rupture of the cartilage to a slight crack of the bone to a piece of the bone breaking off within the joint.
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.
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.
The patella, also called the kneecap, is a small flat triangular bone located at the front of the knee joint. The kneecap or patella is a sesamoid bone that is embedded in a tendon that connects the muscles of the thigh to the shinbone (tibia). The function of the patella is to protect the knee joint from the front.
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.
Matrix-Induced autologous chondrocyte implantation is an innovative, FDA-approved cartilage restoration procedure that uses your own cells to repair cartilage defects in your knee.
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.
Meniscal repair may be performed either by open surgery under direct vision or minimally invasively using an arthroscope, which is a thin tube fitted with a camera that can be inserted into the knee through a very small incision to locate and repair the damaged meniscus.
An autograft refers to using organ or tissue (bone, cartilage, tendon or skin) from the same person to transplant elsewhere on their body.ACL reconstruction with hamstring autograft method is a surgical procedure to replace the torn ACL with part of the hamstring tendon taken from your leg.
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.
The surgical repair of the completely torn ligament involves reconstruction of the torn ligament using a tissue graft taken from another part of the body or from a donor.
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 the smooth movement of the cartilage-covered articulating surfaces of the joint.
Physical Therapy for Knee 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 the smooth movement of the cartilage-covered articulating surfaces of the joint.
The knee can be divided into three compartments: patellofemoral, the compartment in front of the knee between the kneecap and thighbone, the medial compartment, on the inside portion of the knee, and lateral compartment which is the area on the outside portion of the knee joint.
The TLS short graft ACL reconstruction is an advanced surgical technique performed to repair a torn ACL ligament in the knee. It involves the use of a tape locking screw (TLS) system that enhances the strength and mobility of the reconstructed ACL tendon, allowing the return to sports or an active lifestyle.
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. Knee replacement surgery involves replacing worn or damaged joints with implants to reduce pain and improve movement.