In this video, we're going to talk about additional features that are found in just some synovial joints, but not in all synovial joints. And the first are going to be bursae. Bursae are synovial fluid-filled sacs that are strategically located in some synovial joints to reduce friction between ligaments or tendons and other tissues. By reducing friction, they also help to prevent damage. A tendon sheath is really just an elongated bursa, so it's just a longer bursa that wraps around and protects a tendon, as its name implies. It therefore helps to reduce friction and again prevent damage during the movement of some synovial joints.

Next on our list are fatty pads, which, as their name implies, are going to be made up of fat or adipose tissue. These fatty pads are going to be present in the knee joint and the hip joints, which are load-bearing joints that need to bear the weight of our body. They do need these extra layers for cushioning. The fatty pads help to provide an extra layer of cushioning between the outer fibrous layer and the inner synovial membrane of the articular cartilage, again, of some joints, specifically the knee and hip joints.

Next on our list are articular discs, which are also known as menisci. These are discs of fibrocartilage or of fat that divide the synovial cavity into two spaces. These articular discs have many different functions, including acting as shock absorbers to protect those joints. Articular discs are found in the knee and the jaw and in a few other joints as well.

Let's take a look at our image down below where we can start to visualize some of these additional features. Notice on the left-hand side, we're focusing on the knee joint. You can see that this is a zoom-in of the knee joint. What you'll notice is that there are these purple structures throughout the knee joint, and those purple structures are representing the bursae or bursa for the singular form. The image on the right over here is a zoom-in of the shoulder joint. What you'll notice is that the shoulder joint also has a bursa strategically located right here in this position. Again, the bursa is just a synovial fluid-filled sac that's going to help reduce friction within that synovial joint.

Notice that the shoulder joint has a tendon sheath, which is just an elongated bursa that wraps around a tendon. You can see that there's a tendon here, and the tendon sheath is wrapping around that tendon, again to help reduce friction and prevent damage. Next, over here, what we have is a fatty pad. You can see that this fatty pad is located right here in this position and it is strategically located in the knee joint to help provide an extra layer of cushioning. What we have is an articular disc or a meniscus located right here in this position, and you'll notice that there's another one over here as well. What it does is it separates the synovial cavity into two separate spaces, which can help to relieve stress and redirect synovial fluid into specific regions to relieve the synovial joint of stress, provide stability, and act as a shock absorber as well.

This here concludes our brief lesson on these additional features that again are found in just some synovial joints, not in all synovial joints, and we'll be able to get some practice applying these concepts moving forward. I'll see you all in our next video.