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Your Knee Anatomy


Your Knee Anatomy

Smith & Nephew

Anatomy and Function of the Knee

No matter what you do for work or pleasure - standing, sitting, running to the grocery store or running with a football - the knee is truly one of the most complex joints of the human body.

 

Simply put, the knee works in a similar fashion to a modified hinge on a door. It not only bends back and forth like a hinge, but it also has a complex rotational component that occurs whenever you bend (this is called “flexion”) as well as when you straighten it (this is referred to as “extension”). It is a major weight-bearing joint that is held together by muscles, ligaments and soft tissue.

 

Cartilage can be found inside the joint and provides shock absorption which comes into play whenever you walk, run, lift, climb stairs and pretty much any other impact activity you can name. See the below illustration for more on the components of the knee.

 

Your knee is comprised of four main components:

  • Bones
  • Ligaments
  • Cartilage
  • Tendons


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Smith & Nephew

Your knee is made up of the femur (thighbone), the tibia (shinbone) and the patella (kneecap). The femur and tibia come together to form a hinge with the patella in front of them, which provides protection for the joint. All the while, the patella moves in a sliding action up and down in a groove in the femur. This groove is called the femoral groove and the sliding occurs whenever you bend or straighten your knees.

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The job of the ligaments is to ensure that the components of the knee are held together and kept stable. The medial (inner) collateral ligament (MCL) and lateral (outer) collateral ligament (LCL) limit sideways motion of the knee. At the same time, the posterior and anterior cruciate ligaments (PCL and ACL) limit forward motion of the knee bones, thus keeping them stable. Without this stability, you may feel that your knee is simply giving out from under you.

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Each knee has two cartilage structures called menisci, which sit between the femur and the tibia. These strong but flexible menisci act as shock absorbers. They also stabilize and evenly distribute your body weight across the knee joint. Oftentimes, a torn meniscus is called “torn cartilage.” The menisci are one of two types of cartilage in the knee. The second type, articular cartilage, is a smooth and very slick material which covers the end of the femur, the femoral groove, the top of the tibia and the underside of the patella. All of these enable the knee and its bones to move smoothly.

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The job of tendons is to connect muscles to the knee. The quadriceps muscle on the front of the thigh is connected to the top of the patella by the quadriceps tendon, which covers the patella and becomes the patellar tendon. The patellar tendon then attaches to the front of the tibia. The hamstring muscles in the back of the leg attaches to the tibia at the back of the knee. The quadriceps muscles straightens the knee while it’s the job of the hamstring muscle provides the knee’s bending motion.

 

How does arthritis affect your knee joint?

  • Osteoarthritis of the Knee
    Explore osteoarthritis, the most common form of arthritis and a progressive, degenerative disease that most often occurs in middle-aged and older adults.
  • Rheumatoid Arthritis of the Knee
    Explore rheumatoid arthritis, causes, symptoms and information on non-surgical and surgical treatment options.
  • Post-traumatic Arthritis of the Knee
    Learn more about post-traumatic arthritis caused from knee injury to pain symptoms, knee swelling and joint stiffness.

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