Hi, and welcome back. This is lecture two of Section four. After this lecture you will know all about the muscles that enable movements of the knee. The knee can flex and extend course, but when it is flexed even just a little, it can rotate both to the medial and lateral side. The tibia actually pivots underneath the femoral compounds. This lecture is going to be a rather short one.

And as usual, we start with flexion. Here you see the table with the muscles involved. For knee flexion, we see familiar names in the table. The hamstrings, or Ischia, crew or muscles are by articular as I mentioned in the previous lecture. The consequence of this is that they not only extend the hip joint, but our active knee flexion as well. As a matter of fact, flexing the knee is seen as their main activity.

The new muscle we see here is gastrocnemius. This muscle is part of triceps Hooray. The cuffs main muscle. The two by articular heads of triceps hooray are gastrocnemius the medial and lateral head. Both heads start at the posterior side of the medial and lateral combine of femur and they inserted with a common tendon at calcaneus. This tricep tendon is called Achilles tendon.

The third head of triceps is called Sony's and lies underneath the two heads of gastrocnemius. It arises from the posterior side of fibular head and two inches below that and from tibia, and then joins the gastrocnemius tendon for inserting at calcaneus. solely is not active in new movements. Another muscle is plant aureus Which is actually part of lateral gastrocnemius arising right above it and inserting via Achilles tendon as well. The last flexor is pretty is deep in the knee cavity it arises at the lateral side of the lateral compile of femur and inserts just distally off the knee joint at the proximal posterior side of tibia. The only muscle for extending the knees quadriceps.

This muscle has four heads as you will understand the lumbar articular head rectus femoris we already know from flexing the hip. The other three heads are vastus medialis fastest lateralis investors intermediate there aren't origins are at the posterior side of the shaft of the femur. thin line for vastus medialis and lateralis. You see it here and here and then vastus medialis and lateral is fold around femur to the front side and cover first intermediate, which has a very large surface of origin that stretches out from posterior to anterior over femur. At the front side vastus medialis and vastus lateralis both have an extra origin right next to the origin of fastest intermediate. All foreheads of quadriceps inserted the tibial tuberosity via one common tendon named patellar ligament.

The patella is embedded in quadriceps just where it passes on to the tendon. Its function is being leveraged to enable quadriceps to yield more force. Let's talk about rotations in the knee As you can see, there are no new muscles here, but the familiar muscles have more than one function. The group that immediately rotates the tibia, are the muscles that attach at the medial side of the tibia. So when they contract and therefore become shorter, the tibia is rotated to the medial side like a puppet on a string. For lateral rotation, there is only one muscle that causes this movement, biceps femoris.

Well, this is the end of lecture two. In the next lecture, we will look at the movements of the ankle and toes. I hope to see you back in lecture three