Today we will discuss the muscles of the lower limb. Objectives here are to name the muscles that are responsible for the major movements. There are many, many muscles in the lower limb and we could spend several hours discussing them in detail, but there's certain muscles that attract our attention for a series of reasons. The first reason is we're interested in muscles that we can see because we can look at them, we can compare right side to left side. We can make an assessment about whether the muscle is atrophied perhaps from a disease or lack of exercise. We're also interested in muscles that we can test. There are many small muscles that have relatively important functions but they're difficult for us to assess them individually. So we're interested in muscles that we can test. We're also interested in muscles that have a reflex. And this is important to us because if we can tap on the tendon of that muscle and look at its response, we can make an assessment about the condition of the central nervous system for example. There are other muscles which have relatively minor roles but are important to us diagnostically because they can help us discriminate injury from one region from another. And finally, other muscles are important to us because they serve as landmarks. They help us organize the structures that pass nearby them. We begin with the iliopsoas muscle. The iliopsoas muscles is actually two muscles, the psoas muscle, the long muscle that arises from the lateral border of the vertebral bodies and the ilio muscle which arises from the iliac fossa. These muscles attach together across the hip joint onto the femur and they're the main fletchers of the hip. The gluteus maximus, the large buttocks muscle is a major hip extensive. And if you think about getting up from a sitting position, it's the gluteus maximus that's the most effective in extending the hip when it's in a flexed position. The gluteus medius is deep below the gluteus maximus and it's an abductor of the hip. But its main role actually is in gate in walking. It stabilizes the pelvis when the opposite leg is lifted off the ground. In addition to its abduction function, the anterior fibers of the gluteus medius are involved in medial rotation of the hip. If we look at the hip joint posteriorly, we can see several muscles, the piriformis muscle, the obturator internus, the quadratus femoris. These are the lateral rotator group and are responsible for lateral rotation of the hip. From an interior view here, we can see the main adductors of the hip, the abductor longus and the abductor magnus. If we look at the anterior thigh here, we can see the quadriceps muscle named for the fact that it has four components. These muscles act together the four of them to extend the knee. If we look at a posterior view of the thigh, we can see the hamstrings. And the hamstrings because of the fact that they cross both the hip joint and the knee joint have what seems to be a confusing action, they extend the hip but they flex the knee. And it's because of their relative insertion points and places where they cross the joints that produce these actions. If we look now at the posterior leg, we see the gastrocnemeus and soleus. There's a medial and lateral gastrocnemeus and deep to them is soleus. These muscles attach together on the achilles tendon which attaches to the calcaneus. And they plantar flex how you point the toe. Anteriorly on the leg, we see the tibialis anterior muscle which dorsiflexes the ankle and inverts. Dorsal flexion of the ankle turns out is very important in walking because as we lift our foot off the ground, our toe would drop if not for the function of the tibialis anterior. So it keeps us from tripping. On the lateral leg, we see the fibularis muscle. There are actually two muscles, a fabulous longus and a fibularis brevis. These evert the ankle. We don't really think about inversion and the version very much but it turns out there they're very important functions because these muscles act together to stabilize the ankle to keep us if you will from turning our ankle. And they're also much more active when we're walking on even terrain. So, these muscles are small and the amount of movement they produce is not very large, but we need to think about them in terms of their functional role. We see the extensive hallucis longus. Again, a small muscle that extends lifts the great toe off the ground and it turns out that this muscle is important functionally because it's controlled mostly by one spinal nerve and either weakness or lack of weakness in that muscle can help us discriminate injury from one part of the a nervous system to the other. So now that we've been through these muscles here, here's a summary that we've just discussed. And now we'll think about how much we've been able to remember. This is a non-graded self assessment quiz. So, don't feel nervous about it, just think about it for a minute and we'll go through each muscle separately. So let's look at the gluteus maximus. Remember what we said and what we said about that. He said that it extends the hip. That's great. We recall that there are two muscle groups that extend the hip but it's a gluteus maximus that's most active when we're when the hip is flexed and we're standing up from say from a sitting position. Quadriceps muscle extends the knee recall that it's a muscle that has four components and that's why it's called because the quadriceps. Now if we think now about the tibialis anterior. We recall that it dorsiflexes the ankle and that's an important movement because it keeps us from tripping as we lift our foot off the ground. The gastrocnemei and the soleus. Plantarflexes the ankle and these muscles are important in pushing off as we as we step forward. The iliopsoas muscle. Again, we recall two muscles and insert together so they have a combined name, the ilio and the soleus flex the hip. And then the hamstrings. Flex the knee. And as some of you thought also well extends the hip. That's correct as well because of the fact that it crosses the both joints, it extends at the hip that flexes at the knee. Thank you.
