The knee is a gentle joint with many tendons and ligaments running through it. One of the keys to understanding the knee and making sure that the way you use it is most effective, is knowing what it does.
The knee is used to perform knee flexion- or moving your lower leg towards backwards and up so that it touches your glutes. This is particularly prominent in activities such as running or squatting. Another movement performed by the knee is knee extension- this is bringing the lower leg up from a curled position, tucked in by the hamstrings, to a straightened position. In order to do both of these you need muscles, and there are many needed to perform all of its functions.
To perform knee flexion your hamstrings are used. Your hamstrings are made up of three muscles all in close proximity and performing similar functions. They are the biceps femoris, semitendinosus and the semimembranosus. As mentioned previously they are particularly used when you run or squat and are best trained by using a full ROM (range of motion). Examples of effective exercises would be a squat or deficit deadlift as a compound movement and a hamstring curl as a targeted isolation muscle exercise.
The other action of the knee is to extend of straighten the lower leg. This uses the muscles of the quadriceps group namely the vastus medialis, vastus intermedius, rectus femoris and the vastus lateralis. These muscles are best trained using something like a squat as a compound movement or a leg extension machine as an isolation movement.
Now to move on to the bones that are in and around the knee. Because the knee is a joint (hinge joint) it will be the meeting point of two or more bones. In this case the bones n question are the femur or thighbone, the tibia or shinbone and the patella or kneecap. Both the femur and tibia are strong bones with the former being encased by a large layer of muscle. As for the tibia it is a very dense bone as it holds the vast proportion of the bodies weight. The patella is simply their to protect the inner workings of the knee, as you will find out next, they are quite delicate.
There are many ligaments present in the knee- the first is the lateral collateral ligament or LCL that runs on the outside of the knee joint. It runs from your femur or thighbone to the top of your fibula, the bone adjacent to your tibia. On the other side of the joint is the medial collateral ligament or MCL. This runs between your femur and the top edge of your tibia. These two ligaments work together to stop side-to-side movement of the knee joint and help prevent rotation between your femur and your shinbone or tibia. The next two work together nicely as well- inside the joint itself run two ligaments in a sort of X-shape and they are known as the cruciate ligaments. The one that runs in front is known as the anterior cruciate ligament or more commonly the ACL and the one that runs in behind is known as the posterior cruciate ligamnet or PCL. The role of these two is to stop the tibia moving in front or behind the femur.
This will pretty much be the end of this post but before you go we have a few other things to discuss. First of all the meniscus- these are shock absorbers that protect the top of the two bones and namely the growth plates of the femur and tibia. These growth plates are what the body uses to grow the femur and tibia respectively, all that I will say here is to protect them because even a slight knock will be very painful.
Hope you enjoyed this body mechanics post, sorry if its too sciencey but understanding how the body works is a key part of getting the most out of your body.