The Knee Joint Complex, Utilitarian, and Essential!

Editor's Note: When you see these three dots surrounded by a gray rectangle — 1 — you can click on it to get further information about the topic. Click a second time, and the message goes away.

This article was edited and updated on March 19, 2018.

The Importance of the Knee Joint

It may seem obvious how important the knee joint is: It allows us to bend and straighten our leg, and it supports our body while standing, walking, getting up from the floor, or climbing stairs. The knees work in conjunction with our feet and ankles to help us keep our balance.

Those who have ever injured their knees know how much we use them every day. Far too often, we take them for granted.

The Bones

The knee joint is like a hinge, and three bones are involved in its structure:

The femorotibial joint is where the femur and tibia come together.

The patellofemoral joint is where the patella and femur form a junction.

These two joints work together to allow the knee to bend and straighten. If you have a total knee replacement, it is these joints that are replaced.

Cartilage and Ligaments

We wouldn't like it much if those bones just rubbed against each other.

To prevent bone from rubbing on bone, the surfaces of all three bones are covered with a smooth gliding surface known as articular cartilage.

As well, there is cartilage that cushions the space between the two bone ends. The inner one is called the medial meniscus, while the outer one is called the lateral meniscus. Like the deltoid that shapes the shoulder, the meniscus cartilages form the shape of the knee. They also act as shock absorbers by distributing weight and reducing friction.

In addition to cartilage, there are four very important ligaments that surround, support and stabilize the knee. 2 They are:

What can go wrong?

If damage is done to the smooth lining cartilage of the knee — and this usually happens as we age — then the surfaces of the bone begin to rub together. This causes pain, swelling, and stiffness. It's called osteoarthritis, and it's a common reason to have a knee replacement.

Some other causes of knee joint destruction are:

Some Common Injuries to the Knee

The knee is the largest and one of the most easily injured joints. It is formed by three bones: the lower end of the femur which rotates on the upper end of the tibia, and the knee cap (patella) which slides in a groove on the end of the femur.

Injuries often occur when changing or twisting direction rapidly, slowing down when running, and landing from a jump.

Knee injuries are common in contact sports, but they can happen in falls and accidents as well. Injuries to the MCL (medial collateral ligament) usually are caused by contact on the outside of the knee. A blow to the front of the knee or a misstep can cause injury to the PCL (posterior cruciate ligament). In athletic activities, meniscus tears usually occur when twisting, cutting, pivoting, or decelerating.

Two common injuries to the knee are:

The most important advice is to seek medical treatment as soon as possible and follow the prescription for treatment and rehabilitation.

Taking care of Your Knees

The trick to strengthening muscles around any joint is to find the appropriate exercise. Keep these rules in mind if you have injured your knee, or you just want to strengthen it, before embarking on any exercises:

Other articles related to the knee:

I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.

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  1. These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. 

  2. Thanks to Fitness Theory Manual (2003, Canadian Online Fitness) and Special Populations (On the Edge Fitness) for their diagrams of the knee.