Knee Anatomy
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.
Knee Pain
Knee pain is a common condition affecting individuals of various 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.
Knee Arthritis
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.
Knee Osteoarthritis
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).
Meniscal Tears
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.
Meniscal Injuries
Meniscal tears are one of the most common 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.
Jumper's Knee
Jumper’s knee, also known as patellar tendinitis, is inflammation of the patellar tendon that connects your kneecap (patella) to your shinbone. This tendon helps in the extension of the lower leg.
PCL Injuries
Posterior cruciate ligament (PCL), one of the four major ligaments of the knee, is situated at the back of the knee. It connects the thighbone (femur) to the shinbone (tibia).
Patellofemoral Instability
Patellofemoral instability means that the patella (kneecap) moves out of its normal pattern of alignment. This malalignment can damage the underlying soft structures such as muscles and ligaments that hold the knee in place.
Quadriceps Tendon Rupture
The quadriceps can rupture after a fall, direct blow to the leg and when you land on your leg awkwardly from a jump. Quadriceps tendon rupture most commonly occurs in middle-aged people who participate in sports that involve jumping and running.
Patellar Tendon Rupture
The patellar tendon works together with the quadriceps muscle and the quadriceps tendon to allow your knee to straighten out. Patella tendon rupture is the rupture of the tendon that connects the patella (kneecap) to the top portion of the tibia (shinbone).
Knee Fracture
A fracture is a condition in which there is a break in the continuity of the bone. In younger individuals, these fractures are caused by high energy injuries, as from a motor vehicle accident.
Posterolateral Instability
Posterolateral instability, also known as posterolateral rotatory instability (PLRI), is a common pattern of knee instability that results from injuries to the structures that support the outside of the knee joint, the posterolateral corner.
Chondromalacia Patella
Chondromalacia patella is a common condition characterized by softening, weakening and damage of the cartilage. The condition is most often seen in young athletes and older adults who have arthritis of the knee.
Kneecap Bursitis
Bursitis refers to the inflammation and swelling of the bursa. Inflammation of the bursa in front of the kneecap (patella) is known as kneecap bursitis or prepatellar bursitis.
Iliotibial Band Syndrome
Iliotibial band syndrome is an overuse injury resulting from the inflammation of the iliotibial band. It occurs when the iliotibial band and the lower outside portion of the thighbone at the knee joint rub against each other.
Shin Splints
Shin Splints is an overuse injury resulting from the inflammation of the iliotibial band. It occurs when the iliotibial band and the lower outside portion of the thighbone at the knee joint rub against each other.
Knee Injury
Pain, swelling, and stiffness are the common symptoms of any damage or injury to the knee. If care is not taken during the initial phases of injury, it may lead to joint damage, which may end up destroying your knee.
Knee Sprain
Knee sprain is a common injury that occurs from overstretching of the ligaments that support the knee joint. A knee sprain occurs when the knee ligaments are twisted or turned beyond its normal range, causing the ligaments to tear.
MCL Sprains
The medial collateral ligament (MCL), a band of tissue present on the inside of your knee joint, connects your thighbone and shinbone (bone of your lower leg). The MCL maintains the integrity of the knee joint and prevents it from bending inward.
Multiligament Instability
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).
Patella Fracture
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.
Knee Dislocation
Knee dislocation is a condition that occurs when the bones that form the knee joint, namely the femur or thigh bone get separated from the shin bone.
Articular Cartilage Injury
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.
Knee Sports Injuries
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..
Patellar Tendinitis
Patellar tendinitis, also known as "jumper's knee", is an inflammation of the patellar tendon that connects your kneecap (patella) to your shinbone. This tendon helps in extension of the lower leg..
Osgood Schlatter Disease
Osgood-Schlatter disease refers to a condition in older children and teenagers caused by excessive stress to the patellar tendon (located below the kneecap). Participants in sports such as soccer, gymnastics, basketball, and distance running are at higher risk for this disease.
Quadriceps Tendon Rupture and Repair
The quadriceps can rupture after a fall, direct blow to the leg and when you land on your leg awkwardly from a jump. Quadriceps tendon rupture most commonly occurs in middle-aged people who participate in sports that involve jumping and running.
Tibial Eminence Fractures
The tibia or shin bone is a major bone of the leg which connects the knee to the ankle. A fracture or break in the upper part of the tibia is known as a proximal tibial fracture and commonly occurs just below the knee joint.
Anterior Knee Pain
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.
Osteochondritis Dissecans of the Knee
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.
Runner's Knee
Patellofemoral pain syndrome also called runner’s knee refers to pain under and around your kneecap. Patellofemoral pain is associated with a number of medical conditions such as anterior knee pain syndrome, patellofemoral malalignment, and chondromalacia patella.
Knee Angular Deformities
Angular deformities of the knee are variations in the normal growth pattern during early childhood and are common during childhood.
Patellofemoral Arthritis
Patellofemoral arthritis is an inflammatory condition characterized by loss of the smooth cartilage between the kneecap (patella) and the underlying femoral (thigh) bone in the knee joint.
Periprosthetic Knee Infection
A very small percentage of patients (less than 1%) who undergo knee replacement may develop an infection around the knee joint. This infection is called a periprosthetic knee infection.
Knee Arthroscopy
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 you will usually be discharged from the hospital on the same day of surgery.
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 an artificial prosthesis.
Revision Knee Replacement
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.
Unicondylar knee Replacement
Unicompartmental knee replacement or unicondylar knee replacement is a minimally invasive surgery in which only the damaged compartment of the knee is replaced with an implant.
Minimally Invasive Knee Joint Replacement
Total knee replacement is a very successful surgical treatment for knee arthritis. Over the years, minimally invasive knee replacement surgical techniques have been developed to lessen tissue trauma and improve patient outcomes.
Meniscus Replacement
The meniscus is a soft, fibrous disk of cartilage in your knee joint that sits between the femur (thighbone) and the tibia (shinbone). Also called fibrocartilage, it cushions and stabilizes the joint, acting as a smooth surface for the joint to move on to prevent wear and tear.
Patellar Tendon Repair
Patellar tendon repair is the surgery performed to reattach the torn tendon to the kneecap and to restore normal function in the affected leg.
Quadriceps Tendon Repair
Quadriceps tendon is a thick tissue located at the top of the kneecap. The quadriceps tendon works together with the quadriceps muscles to allow us to straighten our leg.
Knee Fracture Surgery
A knee fracture is a broken bone or a crack in or around the joint of the knee. This can involve the tibia (shin bone), the kneecap (patella), or femur (thighbone) where they connect with the knee.
ACL Reconstruction
ACL (anterior cruciate ligament) reconstruction is a commonly performed surgical procedure. With recent advances in arthroscopic surgery, it can now be performed with minimal incision and low complication rates.
PCL Reconstruction
PCL reconstruction surgery is a procedure to correct torn posterior cruciate ligament (PCL) in the knee using a tissue graft taken from another part of the body, or from a donor.
LCL Reconstruction
LCL reconstruction is a surgical procedure to repair torn or damaged lateral collateral ligament in the knee using a tissue graft taken from another part of the body, or from a donor.
Posterolateral Corner Reconstruction
Posterolateral corner injury is damage or injury to the structures of the posterolateral corner. The structures of the posterolateral corner include the lateral collateral ligament, the popliteus tendon, and the popliteo-fibular ligament.
Knee Ligament Reconstruction
Knee ligament reconstruction is a surgical procedure to repair or replace damaged ligaments of the knee joint. The surgery can be performed using minimally invasive techniques.
Multiligament Reconstruction of the Knee
Multiligament knee reconstruction is a surgical procedure to repair or replace two or more damaged ligaments of the knee joint. The surgery can be performed using minimally invasive techniques.
Medial Patellofemoral Ligament Reconstruction
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.
MCL Reconstruction
MCL reconstruction is a minimally invasive surgical procedure in which a tendon graft is utilized to reconstruct the injured MCL.
Compartment Decompression
Compartment decompression, also called ‘decompressive fasciotomy’, is a surgical procedure to treat a painful knee condition known as “compartment syndrome”.
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Cartilage Restoration of the Patellofemoral Joint
The articular or hyaline cartilage is the tissue lining the surface of the two bones in a 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.
Patellofemoral Realignment
Patellofemoral realignment is a surgical procedure performed to treat symptomatic patellofemoral instability that does not respond to nonsurgical treatment measures.
Arthroscopic Debridement
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.
Tibial Derotational Osteotomy
Tibial derotational osteotomy is a surgical procedure employed to treat rotational deformities of the tibia, such as tibial torsion. This is a condition characterized by twisting of the tibial bone of the lower leg, causing malalignment of the knee and ankle with an appearance of an inward or outward turning of the feet.
Meniscal Transplantation
The meniscus is a C-shaped cartilage ring that acts as a cushion between the shinbone and the thighbone. Each of your knees has two menisci - one on the inside (medial aspect) and the other on the outside (lateral aspect)of your knee.
Meniscectomy
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.
Distal Femoral Osteotomy
An osteotomy is a surgical procedure that involves cutting of bone. The distal femur is part of the femur (thighbone) just above the knee joint. Distal femoral osteotomy is performed to correct knee alignment which can lead to excessive loading and degeneration of one side of the knee joint.
Chondroplasty
Chondroplasty is a surgical procedure to repair and reshape damaged cartilage in a joint. The procedure involves smoothing degenerative cartilage and trimming any unstable flaps of cartilage.
Knee Cartilage Restoration
Knee cartilage restoration is a surgical technique to repair damaged articular cartilage in the knee joint by stimulating new growth of cartilage or by transplanting cartilage into areas with defects in order to relieve pain and restore normal function to the knee.
Distal Realignment Procedures
Distal realignment procedures, also known as tibial tubercle transfer (TTT) procedures, are performed to reposition the kneecap after subluxation or dislocation by realigning the tendon under the kneecap to the underlying tibial tubercle.
Cartilage Replacement
Cartilage replacement is a surgical procedure performed to replace the worn-out cartilage with new cartilage.
Subchondroplasty
Subchondroplasty is a minimally invasive procedure that is performed to specifically repair chronic BMLs by filling them with a bone substitute material. The bone substitute is then slowly resorbed and replaced with healthy bone, repairing the bone defect.
Partial Meniscectomy
Partial meniscectomy is a surgical procedure to remove the torn portion of the meniscus from the knee joint.
Cartilage Microfracture
Cartilage microfracture is a surgical procedure performed to replace the worn-out articular cartilage with new cartilage.
High Tibial Osteotomy
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.
Tibial Tubercle Osteotomy
Tibial tubercle osteotomy is a surgical procedure that is performed along with other procedures to treat patellar instability, patellofemoral pain, and osteoarthritis.
Meniscal Surgery
Meniscal surgery is a surgical procedure employed for the treatment of torn or damaged meniscal tissues in the knee. It is mostly performed as a minimally invasive keyhole procedure.
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.
Intraarticular Knee Injection
Knee pain and stiffness can be disabling and difficult to treat. It can limit an individual’s lifestyle and negatively impact body image and emotional well-being.
Non-Surgical Knee Treatments
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.