14 Anterior, Medial, and Lateral Thigh | Anterior and Lateral Leg | Dorsal Foot
Learning Objectives:
- Identify the muscles of the anterior thigh, medial thigh, lateral thigh, anterior leg, lateral leg, and dorsal foot.
- Using the muscle charts as a guide, identify the action, origin, insertion, and innervation for the muscles of the anterior thigh, medial thigh, lateral thigh, anterior leg, lateral leg, and dorsal foot.
- Describe how structure governs function and provide examples based on muscle orientation and actions.
- Identify the anatomy of the knee joint.
- Identify the anatomy of the ankle joint.
Terms to Know
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Muscles of the Lower Extremity
Muscles of the Leg
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Muscles of the Leg (continued…)
Muscles on the Dorsal Aspect of the Foot
Joints of the Lower Extremity
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Introduction
In this lab you will explore the muscles of the anterior thigh, medial thigh, lateral thigh; anterior compartment of the leg; lateral compartment of the leg; and the dorsal aspect foot. You will also explore the knee and ankle joints. You will examine both the muscles and joints using videos from the digital atlas, lower extremity dissections, and image slideshows. Use the muscle charts and available resources to guide your learning of the origin, insertion, action, and innervation.
Dynamic vs Static stability of the Knee Joint
An interesting clinical point to consider is dynamic vs. static stability of the knee joint. Static stability comes from all the non-contractile elements of a joint (e.g bone shape, ligaments, cartilage, capsule) and gives us many structure governs function examples. The dynamic stability refers to joint stability provided by muscle actions. The knee provides two great examples: The action of the quad muscle directly support the PCL ligament (a ligament designed to protect posterior translation of the tibia on the femur) and the hamstrings directly support the ACL ligament (a ligament designed to protect anterior translation of the tibia on the femur).
Lab Activities
Activity 1: Anterior, lateral, and medial thigh
Explore the muscles of the anterior, lateral, and medial thigh using the videos posted on the Lab 9 Canvas page and the atlases and other resources available to you through the “Resources” page of Canvas.
- Anterior thigh
- Observe the psoas major, iliacus, or iliopsoas muscles. The psoas major originates on the lumbar vertebrae, and it merges with the iliacus to form the iliopsoas. These muscles flex the hip.
- Observe the sartorius. This long, thin muscle runs across the anterior thigh from the ASIS to the pes anserine insertion on the tibia. This is the longest muscle in the body.
- Now observe the four muscles that make up the quadriceps muscle group. The rectus femoris is the superficial muscle located on the midline of the thigh. It crosses both the knee and hip joints. The vastus lateralis and vastus medialis are located just lateral and medial to the rectus femoris, respectively. The vastus intermedius is deep to the rectus femoris.
- Medial thigh
- First observe the gracilis. This muscle is long and thin, and it inserts at the pes anserine insertion of the proximal medial tibia.
- Observe the adductor magnus. This large muscle has both hamstring and adductor parts. The adductor portion inserts just superior to the medial condyle of the femur at the adductor tubercle.
- Observe adductor longus, adductor brevis, and pectineus. The adductor longus is thinner, longer, and anterior to the adductor brevis. Pectineus is also deep to adductor longus.
- The medial thigh muscles appear somewhat fanned out along the medial thigh. All medial thigh muscles have an attachment on the pubis. They insert on the femur (except gracilis), in the following order from superior to inferior: Pectineus, adductor brevis, adductor longus, adductor magnus, and gracilis, which inserts onto the tibia at the pes anserine insertion.
- Lateral thigh
- Near the hip, observe the tensor fasciae latae (TFL) on the lateral aspect of the thigh. The TFL anteriorly and gluteus maximus posteriorly both attach to a long, flat, tendon-like, thick fascial layer called the iliotibial tract (IT band). The IT band inserts at Gerdy’s tubercle on the lateral aspect of the proximal tibia.
ACTIVITY 2: THE KNEE JOINT
Observe the following structures of the knee joint:
- Observe the tibial plateau and the medial and lateral menisci. The menisci function as cushions and shock absorbers for the knee joint. The lateral meniscus is more “O” shaped, while the medial meniscus is more “C” shaped.
- The collateral ligaments blend into the capsule of the knee joint. The medial collateral ligament protects against valgus forces at the knee, in which the knee bends inward in the coronal plane and opens the medial joint space. For example, a valgus force could occur when a football player hits the lateral aspect of another player’s knee during a tackle. Now view the lateral collateral ligament. This ligament prevents against varus forces, which would result in the knee bending out laterally in the coronal plane and opening of the lateral joint space.
- Deep in the knee, observe the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). Notice how the ACL inserts into the anterior aspect of the tibial plateau, while the PCL inserts onto the posterior aspect of the tibial plateau. Therefore, these ligaments cross each other. The posterior cruciate ligament, or PCL, runs from the inner surface of the medial femoral condyle to the posterior intercondylar area of the tibia. It prevents the tibia from moving posteriorly on the femur. The anterior cruciate ligament, or ACL, is a commonly injured ligament. It runs from the inner surface of the lateral femoral condyle, wraps around the PCL, and inserts onto the anterior intercondylar area of the tibia. This ligament prevents anterior movement of the tibia on the femur, and it is crucial to the integrity and proper function of our knee. Many activities we do biomechanically involve forces that push our tibia anteriorly: walking, running, jumping, and more. If this ligament is damaged, it can feel is if our knee is “giving out.” Forceful movements such as jumping without this ligament are difficult and can result in damage to other structures in the knee.
Activity 3: anterior leg, lateral leg, dorsum of the foot
Observe the following muscles of the leg:
- Anterior compartment of the leg: Observe the muscle that appears to be tightly adhered to the lateral aspect of the anterior tibia. This is the tibialis anterior, and it is the primary dorsiflexor of the foot. Just lateral to it is the extensor digitorum longus. The tendons of this muscle extend to digits 2-5. Unlike the upper extremity, there are two “extensor digitorum” muscles, so it is critical to include “longus” in the name when you are referring to this muscle. Deep to tibialis anterior is extensor hallucis longus. “Hallucis” means “great (1st) toe. Finally, observe the peroneus (fibularis) tertius.
- Lateral compartment of the leg: There are two muscles of the lateral compartment of the leg. Peroneus (fibularis) longus is superficial to peroneus brevis and sends its long tendon under the arch of the foot to insert on the base of the first metatarsal. Peroneus (fibularis) brevis has a shorter tendon that inserts at the base of the 5th metatarsal on the lateral aspect of the foot. These muscles act to evert the foot.
Observe the two muscles on the dorsal aspect of the foot:
- The extensor digitorum brevis muscle extends digits 2-4
- Extensor hallucis brevis extends the great toe.
Activity 4: THE ANKLE (TALOCRURAL) JOINT
Observe the ankle (talocrural) joint, and the ligaments that support it.
- The talocrural joint occurs between the tibia, fibula, and talus. Notice how the fibula projects more inferiorly than the tibia at this joint. This is why we have a greater range of motion with inversion of our ankle (pointing the bottom of the foot inwards), than with eversion (pointing the bottom of our foot outwards). When our foot is at a 90 degree angle to our lower leg, as in standing in anatomical position, our talus is locked into a more stable position between the fibula and tibia. However, when we plantarflex our foot, or point our toe, the talus moves out of this position, and we are more vulnerable to ankle sprains in this position.
- Observe the deltoid ligament on the medial aspect of the ankle.
- Anteriorly, observe the anterior tibiofibular ligament running from the distal tibia to the distal fibula. When a patient incurs a high ankle sprain, the tibia and fibula are forced apparat, and this ligament is injured.
- On the anterolateral aspect, observe the anterior talofibular ligament (ATF). This ligament runs from the talus to the fibula, and it is commonly injured with eversion ankle sprains.
- On the lateral aspect of the ankle, observe the posterior talofibular ligament. This ligament runs from the talus to the fibula posteriorly.
- Finally, view the calcaneofibular ligament, which runs from the fibula to the calcaneus.
Wrap up and clinical connection
For today’s clinical connection you will see two videos discussing injuries to the anterior cruciate ligament (ACL). In the first video, an orthopedic surgeon discusses ACL injuries, risk factors, and surgical outcomes. The second video focuses on the repair of ACL injuries. Use your understanding of the anatomy of the knee to understand why the repair is placed where it is and why the patellar tendon is most commonly used in ACL repairs.