Knee Anatomy (Knee Structure and Function)

As the largest joint in the human body, the knee is a complex yet fascinating biomechanical structure. Designed to bear weight and engage in vigorous movements, understanding its construction is key to learning to care for it better.

Structure of the Knee

The knee is a hinge joint, a type of joint that allows movement along only one plane. In the case of the knee, it can only move in one direction back-and-forth, but not sideways (like a pendulum) or diagonally.

The knee joint joins the thigh bone, the femur (which runs from your hip to knee), to the shin bone (the tibia, or your lower leg). Alongside the tibia runs a skinnier, smaller bone called the fibula. Attached to the front of the femur (at the point where it meets the tibia) is a small piece of bone called the patella, more commonly known as the kneecap.

All these disjointed bones are connected to one another by strong, sturdy ligaments. The femur and tibia are linked by four major ligaments:

  • The anterior cruciate ligament (ACL) connects the femur and tibia at the centre of both bones, and the posterior cruciate ligament (PCL) is located behind the ACL. Together, they prevent the tibia and femur from sliding too far forwards or backwards and thus prevent knee overextension.
  • The medial collateral ligament (MCL) and lateral collateral ligament (LCL) prevent the bones from sliding side-to-side, keeping the knee locked within one plane (it can only move back and forth and not sideways). The MCL runs down the side of the femur and tibia while the LCL connects the fibula to the femur.

You may often hear your athlete friends complaining about “tearing their ACL”. Ligament tears and sprains in the knee are often the results of sports injuries or awkward movements. ACL injuries occur when the knee is bent backwards, side-to-side or twisted, especially as a product of sudden movements such as quick pivots while playing football or sticking an awkward landing after a jump. Due to the sudden, unnatural orientation of the knee, the ACL is overstretched and tears, which is often heard as a popping sound.

Just like most joints in the body, the knee is connected to surrounding muscles such as the hamstrings (back of thigh), quadriceps (front of thigh), calf (back of the shin) and popliteus (back of knee joint). All these muscle groups work to provide extra support to the knee: the hamstrings enable bending and the quadriceps enable flexing or the act of stretching the leg outwards.

Soft, smooth cartilage called meniscus can be found on the base of the femur and the top of the tibia. Cartilage absorbs shock during movement, as well as reduces friction and discomfort caused when the two bones rub against each other.

The function of the Knee

The knee is able to perform four movements. Of these, the two main movements are flexion and extension.

Flexion refers to the act of bending the knee. The knee is flexed when movements such as squatting or kneeling are performed.

On the other hand, extension occurs when stretching out away from the knee. Movements that involve extension include various stretches, stair-climbing and kicking.

Flexion involves bending inward from 90-135°, while extension involves stretching outward from 90-180°, all along a singular plane (Source:×576.png)

The knee is able to execute lateral and medial rotation, albeit with a limited range of motion and only when the knee is flexed at an angle of 30 to 90 degrees. Lateral and medial rotation refers to the ability of the tibia to move inwards or outwards in relation to the femur, such as by kicking towards and away from the other leg like a pendulum.

Lateral rotation involves an outward movement whereas medial rotation goes inwards. Source:

Caring for the Knee

Taking good care of your knee is essential to preserving mobility in your later years. A chiropractor in Singapore would recommend:

  • Maintaining a healthy weight decreases the amount of pressure borne by the knee, thus reducing the risk of wear-and-tear
  • Strengthening your quads and glutes to increase muscle support for the knee
  • Regular physical activity to train your knee’s strength and range of motion
  • Picking the right shoes to reduce pressure on the knee and ease any aches and pains

Stay tuned for our next post on knee osteoarthritis, where we will be discussing exercises to strengthen your knees and condition the surrounding muscles. If you have any concerns about your knee and would like to see a female chiropractor in Singapore, schedule an appointment with us by calling us at 62084669 or dropping us an email!

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