Knee Anatomy

Knee Anatomy

When studying knee anatomy, it is important to realize that the knee joint is one of the most vulnerable and complex structures in the human body. Every year, millions of people visit health practitioners to address various knee injuries caused by overuse, alignment problems, sports or physical activities, and non-sports related trauma to the knee.

To better understand the need for knee bracing, we will quickly take you through the knee anatomy, common injuries, treatment and the role knee braces have in rehabilitation.

Knee Anatomy


The knee is comprised of four primary structures: bones, ligaments, cartilage, and tendons.


The femur, or thigh bone, is the longest bone in the human body. At the bottom of the shaft, the bone widens at the point where it articulates with the lower leg bone (the tibia). The medial and lateral epicondyles are the part of the femur that sit on top of the tibia.

The tibia, or lower leg bone, is also one of the longest bones in the body. Working our way up the shaft of the tibia, we end up at the wider tibial plateau, which is the part that articulates with the femur. Three of the four main ligaments that provide stability to the knee connect the femur to the tibia. (See below.)

The fibula is the long bone of the lower leg that sits to the lateral side of the tibia. It is significant because it is the distal attachment site of the lateral collateral ligament.

The patella, or kneecap, is a small sesamoid bone surrounded by connective tissue. The patella slides through the trochlear groove on the femur during leg flexion and extension.

Knee Anatomy


Ligaments of the knee connect bone to bone and are made of fibrous connective tissue, which control certain motions of the joint.

The Anterior Cruciate Ligament (ACL) stabilizes the knee and minimizes stress across the knee joint. The ACL is located in the center of the knee, and prevents the tibia from moving forward on the femur.

The Posterior Cruciate Ligament (PCL) is located in the center of the knee and crosses behind the ACL. The PCL prevents backward translation of the tibia on the femur.

The Lateral Collateral Ligament (LCL) is located on the outer (lateral) aspect of the knee; it is attached proximally to the lateral femoral epicondyle and distally to the head of the fibula. The LCL helps resist varus motion (outward bowing) of the knee.

The Medial Collateral Ligament (MCL) is located on the inner (medial) aspect of the knee; it connects the femur to the tibia on the medial side of the knee. The MCL helps resist valgus motion (inward bowing, knock-knee) of the knee.
Knee Anatomy


Cartilage is a term that normally refers to the donut-shaped discs located between the femur and tibial plateau called meniscus.

The Medial Meniscus is shaped like the letter “C” and is attached to the MCL. The medial meniscus provides stability and acts as a shock absorber for the knee.

The Lateral Meniscus is shaped like the letter “O” and also provides added stability and cushion for the knee.

Articular Cartilage is another type of cartilage that lines the surface of bones where they articulate with other bones. In the knee, articular cartilage covers the femoral condyles, the tibial plateau, and the posterior (back) portion of the patella. The wearing down of articular cartilage over time is called osteoarthritis.


Tendons work in conjunction with the ligaments to move the knee through natural flexion and extension. They are comprised of strong strings of tissue that connect muscles to bones. Tendons of the knee include the quadriceps tendon, which connects the quadriceps muscle to the patella, and the patellar tendon, which is the end part of the quadriceps tendon. The patellar tendon attaches to the front of the tibia.


Knee injuries can result from overuse, sports or physical activities, alignment issues, and/or direct trauma to the knee, such as a fall or forceful contact to the knee.

The most common ACL injuries occur when there is a lateral blow that puts the knee into a valgus (knock-knee) position accompanied by internal or external rotation of the tibia. Non-contact ACL injuries can also occur when there is abnormal twist or hyperextension of the knee. Articular cartilage damage can also occur during an ACL injury because of this abnormal rotation.

PCL injuries happen when there is a force on the tibia pushing it backward on the femur. These injuries are not usually sports related since the PCL is located deep within the knee and requires violent impact.

The MCL is often injured in conjunction with the ACL, particularly when there is a blow to the lateral part of the knee. With the MCL located on the medial side of the knee, this abnormal motion (from the lateral blow) typically results in stretching or tearing of the MCL.
severe as other ligament tears. An LCL tear usually happens when there is significant impact to the medial aspect of the knee.

Meniscal tears often happen during a significant trauma to the knee (usually in conjunction with ACL or MCL tears), or due to the degenerative process, typically in older patients. When a meniscus tears, it is usually due to twisting or abnormal bending of the knee.


Types of treatment vary based on the severity of the injury, but in general, rest, ice, compression and elevation are prescribed for most minor injuries. Surgery may be needed to alleviate pain or to repair damage in an area that will not heal on its own, such as a ligament tear. Many patients with limited knee function and knee pain resulting from any of the injuries listed above who wish to maintain an active lifestyle are considered candidates for arthroscopic knee surgery. Your primary care physician or orthopedist will determine the best course of treatment.

Ligament reconstructions involve replacing the torn ligament with a graft, either from an autograft (patient’s own tissue) or with an allograft (donor tissue). Autorafts may be taken from the patient's hamstring, quadriceps, or patella tendon, which is then anchored to the bone in place of the torn ligament.

For patients who opt not to have surgery, lifestyle modifications such as weight loss and changes in activity level, rehabilitation to increase strength and flexibility, and the use of NSAIDS (non-steroidal anti-inflammatory drugs) can also be employed. Bracing is another non-invasive method that may be recommended by your physician. Your physician will advise you on which treatment option is best for you.


For patients who undergo surgery, they will likely be fitted with a post-operative brace for a period of time as determined by the physician. This type of brace is used to immobilize and control range of motion immediately following surgery until the patient is back to a more normal, functional state.

After ligament repair, the long-term goal is to return the patient to a normal activity level. Achieving this goal will depend on the function and stability of the knee. Typically, rehabilitation programs include strengthening and flexibility exercises, which improve knee stability by increasing the strength of the muscles that surround the knee, and often involve the use of a functional brace, such as a Breg Fusion or Breg X2K or purposes including stabilization of the knee, protection of the repaired tissue, and/or reducing pressure or load on any articular cartilage repair or injury & either isolated or associated with the ligament tear. Many patients report improved stability with the use of such braces, particularly when engaging in twisting, pivoting, or jumping activities. Additionally, functional braces can decrease the risk of re-injury.

Most functional braces have lightweight frames that incorporate hinges at the knee joint, along with straps that help secure the brace to the knee, thus allowing the knee to flex and extend while providing support. Patients can be fitted with a custom or off-the-shelf brace, depending on the size and shape of the patient's leg, along with any reimbursement restrictions imposed by the patient’s insurance company.

Intermediate knee bracing, which is typically semi-rigid or soft in construction, such as the BREG RoadRunner, can be used for people who have less serious knee injuries. Some indications for use of intermediate bracing include mild cartilage damage, low-grade ligament, muscle or tendon injuries. Please consult your physician for the proper treatment to the above injuries.

Functional knee bracing can also help relieve pain and restore function in patients with unicompartmental osteoarthritis (one side of the knee only). These braces are sometimes referred to as OA or off-loading braces. Off-loading braces are a comfortable, effective option to other conservative (non-operative) treatments for OA, such as injections or oral medication. They provide extended pain relief, while facilitating return to daily activities, and they may help to slow the degenerative process.

Content courtesy of Breg, Inc.