Anatomy 101: Knee (Flexion)
This month we are looking at the knee and more specifically in flexion. Why split this up? Well there are some very distinct differences that happen in the knee during flexion and extension. We will start off this post with just some general, basic anatomy so that we can reference it back to this part of the blog post.
Section I: Structure
The knee is made up of three bones and one supporting structure. These three bones are
- the femur (lateral and medial epicondyle),
- the tibial plateau, and
- the patella (knee cap).
The supporting bone is the fibula that we discussed last month.
[picture of bones of the knee]
Now there are some very important tendons and ligaments that we have to take into consideration, they are:
- Anterior cruciate ligament (ACL), connects from the back of the tibia to the back of the lateral femoral condyle. It prevents the knee from jutting forward under load,
- Posterior cruciate ligament (PCL), connects from the back of the tibia to between the two posterior horns of the menisci it then runs up and attaches to the lateral aspect of the medial condyle. It prevents the knee from jutting backward under load,
- Lateral and medial cruciate ligament (LCL, and MCL respectively), the lateral collateral ligament connects from the lateral epicondyle of the femur and connects with the with the tendon of the biceps femoris. It prevents the knee from jutting outward under load. The medial collateral ligaments connect from the medial epicondyle of the femur to the medial condyle and the upper part of the medial surface of the tibia. This prevents the knee from jutting inward.
- Lateral and medial meniscus. The lateral and medial meniscus acts as shock absorber between the lateral and medial epicondyles and the tibial plateau.
Now for the muscles that control the knee. In this blog post we are only going to focus on the muscles that flex the knee and next month we will look at the muscles that extend the knee.
Section II: Muscles (Flexion)
These muscles have a few jobs other than just pure flexion, I will get into them as we move further.
- Semitendinosus, is a flexor and internal rotator of the knee
- Semimembranosus, is a flexor and internal rotator of the knee
- Gracilis, is a flexor and internal rotator of the knee
- Sartorius, is a flexor and internal rotator of the knee
- Popliteus, is a flexor and internal rotator of the knee and it prevents the femur from slipping forward during a squat
- Tensor Fascia Latae, is a weak flexor and external rotator of the knee when the knee is flexed greater than 30 degrees
- Gastrocnemius, is a weak flexor of the knee and a weak internal and external rotator of the knee
All this information was taken from Physiopedia
Now I know this may not make any sense right now but just bear with me. All of this will at the end of the month when we go through the squat and how these muscles act during movement and it will all be put together and all make sense. Just for now just try to understand the basic anatomy and how this is designed and try to soak it in.