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.