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 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.
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.
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.
Knee Arthroscopy is a common surgical procedure performed using an arthroscope, a viewing instrument, to diagnose or treat a knee problem. It is a relatively safe procedure and most of the patients are discharged from the hospital on the same day of surgery.
ACL preserving total knee replacement is an advanced surgery performed to replace a damaged knee joint with a prosthesis while preserving the anterior cruciate ligament (ACL). The ACL is a very important ligament that runs diagonally across the front of the knee and provides rotational knee stability.
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 failed knee replacement. This procedure involves a partial or complete exchange of the prostheses that were implanted during the original total knee replacement with new prostheses.
Reoperation of a total knee replacement to correct a loosened prosthesis as a result of wear and tear of the prosthetic joint surfaces is known as correction of a loose knee replacement. This procedure involves a complete or partial exchange of prostheses implanted during the original total knee replacement with new prostheses.
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.
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 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.
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, whereas in an arthritic knee the cartilage itself becomes thinner or completely absent.
Traditionally, arthritis in only one compartment of the knee is treated by partial knee replacement surgery. Patellofemoral knee replacement is a minimally invasive surgical option performed in the patellofemoral compartment only, preserving the knee parts not damaged by arthritis as well as the stabilizing anterior and posterior cruciate ligaments (ACL and PCL).
Computer navigation provides your surgeon with real-time 3-D images of your mapped knee and the surgical instruments during surgery. The data for the images is provided by infrared sensors fixed to the bones of the knee and surgical instruments. Their position is tracked by an infrared camera placed above the surgical table, which is connected to a computer.
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.
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.
Robotic-assisted partial knee surgery is an innovative alternative to the conventional surgical procedure to treat degenerative knee diseases such as osteoarthritis. It is performed using robotic-arm technology that allows your surgeon to precisely perform the surgery through small incisions.
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.
Signature knee is a unique knee replacement procedure that is tailored to suit your individual anatomy. The technique utilizes magnetic resonance imaging (MRI) technology to create 3D images of your knee joint, which enables your doctor to efficiently plan your knee replacement surgery.
Bicompartmental knee resurfacing is a less invasive surgical alternative to total knee replacement surgery, where instead of all the compartments being replaced only 2 of the 3 compartments of the knee damaged by arthritis are replaced with a prosthesis. Bicompartmental knee resurfacing preserves the knee parts not damaged by arthritis as well as the stabilizes the anterior and posterior cruciate ligaments (ACL and PCL).
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.
After knee replacement surgery, once the anesthesia wears off, you will start to experience pain, for which your doctor will prescribe medication. You may have to remain in the hospital for a few days depending on your progress and overall health. Remember to get plenty of rest during this initial phase. Your surgical wounds should be monitored for swelling, inflammation and other changes and frequent dressing changes are performed.
Knee implants are artificial devices that form the essential parts of the knee during a knee replacement surgery. The knee implants vary by size, shape, and material. Implants are made of biocompatible materials that are accepted by the body without producing any rejection response. Implants can be made of metal alloys, ceramic or plastic, and can be joined to the bone.