11 Bones of the Lower Extremity
Learning Objectives:
- Name the bones of the lower extremity and describe their functions.
- Identify key landmarks on the bones of the lower extremity and explain their function or purpose.
- Identify and describe the joints of the foot, the bones that make up those joints.
- Explain structure governs function examples from the bones and articulations of the lower extremity (i.e., how is the degree of joint movement determined by the structure of the joint).
terms to know
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Bones of the Lower Extremity
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Bones of the Lower Extremity (Cont.)
Foot and Toe Joints
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Introduction
In this lab, you will begin learning about the lower extremity. During this unit, we will discuss the bones, joints, muscles, nerves, and vasculature that make up our hip and gluteal region, thigh, knee, lower leg, ankle, and foot. Be sure to check the course Canvas page, as we will be providing you with a bony landmark table and muscle table to help clarify what material you will be responsible for and help you learn the material.
This lab focuses on the bones of the pelvis and lower extremity. In this lab, you will view various bone specimens, models, cadaver images, and radiology tools to explore the different bones and joints of the lower extremity, including the pelvis, femur, tibia, patella, fibula, tarsals, metatarsals, and phalanges. Keep in mind that the shapes and orientation of the bones and many of the ligaments are classic “structure governs function” examples. You will be asked to identify specific landmarks on these bones. You are encouraged to look at several different bones of the same type (i.e., more than one femur, from multiple sources). Sometimes, these features are more or less prominent due to anatomical variation. Finally, based on the landmarks, you should identify if individual bones come from the right or left lower extremity. Students are encouraged to reference the muscle and bone landmark charts to better understand origin and insertion landmarks on the bones.
Lab Activities
Activity 1: Bony landmarks of the Lower Extremity
Using the Bone Markings Chart, the bone walk-through videos, and videos of the digital atlas in Canvas identify the bones, bony landmarks, and bony markings of the lower extremities. You can also view these structures in drawing form through the Netter’s atlas and in bone images in the Abrahams’ atlas. In both of these sources, you can also find images with overlays of attachment sites, so you can begin to make connections between the bones and the muscles.
- Observe the bones of the os coxae. The os coxae are the bones of the pelvis, and they are formed by three separate bones that fuse during development: the ilium, ischium, and pubis.
- The ilium is the most superior of the bones of the os coxae. If you “put your hands on your hips,” you are putting your hands on the iliac crest of your os coxae. Use the atlases to identify the following landmarks of the ilium:
- Arcuate line
- Iliac fossa
- Iliac crest
- Anterior superior iliac spine
- Anterior inferior iliac spine
- Posterior superior iliac spine
- Posterior inferior iliac spine
- Greater sciatic notch
- Ala
- The ischium is the posteroinferior bone of the os coxae. We bear weight on our ischial tuberosity every time we sit. Use the atlases to identify the following landmarks of the ischium:
- Ischial spine
- Ischial tuberosity
- Ischial ramus
- Lesser sciatic notch
- Lunate surface
- The pubis is the anteroinferior bone of the os coxae. Use the atlases to identify the following landmarks of the pubis:
- Superior rami
- Inferior rami
- Pubic crest
- Pubic tubercle
- Obturator foramen
- Pectineal line
- The ilium is the most superior of the bones of the os coxae. If you “put your hands on your hips,” you are putting your hands on the iliac crest of your os coxae. Use the atlases to identify the following landmarks of the ilium:
- The femur is the longest bone of our body. It is located between the hip and the knee. The femoral head articulates with the acetabulum of the os coxae to form the hip joint. The fovea is the attachment point for the ligament of the head of the femur or the ligamentum teres. The greater trochanter and lesser trochanter are large sites of muscle attachment on the proximal aspect of the bone. The medial and lateral epicondyles are attachment sites on the distal aspect of the femur. The medial and lateral condyles articulate with the tibia to form the knee joint. Use the atlases to identify the following landmarks of the femur:
- Head
- Fovea
- Neck
- Greater trochanter
- Lesser trochanter
- Gluteal tuberosity
- Linea aspera
- Medial supracondylar line
- Lateral supracondylar line
- Medial condyle
- Lateral condyle
- Medial epicondyle
- Lateral epicondyle
- Intercondylar fossa
- Patellar surface
- The patella is a triangular-shaped sesamoid bone that sits within the tendon of the quadriceps muscle. A sesamoid bone is a bone that is located within a tendon. That the patella only articulates with the femur. It does not have an articulation with the tibia. Observe the medial and lateral articular facets, which are the posterior surfaces that articulate with the femur.
- The tibia and fibula are the bones of the lower leg. Most of our weight is carried on the tibia, while the fibula usually bears at most about 12% of our body weight. In some people, the fibula will bear little or no bodyweight. Superiorly, the medial and lateral tibial condyles articulate with the femur. Inferiorly the tibia and fibula articulate with the talus. The lateral protrusion at the ankle is the lateral malleolus of the fibula, while the medial malleolus of the tibia forms the medial protrusion at the ankle. The tibia and fibula are held together, in part, by the interosseus membrane, which is located between the two bones. Use the atlases to identify the following landmarks of the tibia and fibula:
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- Tibia
- Medial condyle
- Lateral condyle
- Fibular articular facet
- Tibial tuberosity
- Gerdy’s tubercle
- Pes anserine insertion
- Tibial border
- Medial malleolus
- Fibula
- Head
- Articular facet
- Neck
- Lateral malleolus
- Interosseous membrane (between the tibia and fibula)
- Tibia
- The seven tarsal bones form the posterior aspect of the foot. Use the atlases to identify the following tarsals:
- Calcaneus: We bear weight on this bone when we stand, as it forms our heel.
- Talus: This bone articulates with the tibia and fibula to form the ankle joint.
- Navicular: This is the proximal medial bone of the mid-foot. It sits just posterior to the cuneiforms.
- Cuneiforms: These three bones sit anterior to the navicular on the medial aspect of the mid-foot.
- Medial
- Intermediate
- Lateral
- Cuboid: This is the large lateral bone of the midfoot.
- The intertarsal joints are located between the tarsal bones.
- The tarsometatarsal joints are located between the cuneiforms or cuboid and the metatarsal bones.
- The metatarsals are the long bones of the foot. They are numbered I-V based, with I being the great to or “big toe.”
- The metatarsophalangeal joints are located between the metatarsals and the phalanges.
- The phalanges are the most distal bones that form the toes. Toes 2-5 have a proximal, middle, and distal phalanx. The first toe only has a proximal and a distal phalanx, and the first toe is referred to as the hallux.
- The interphalangeal joints are located between the individual phalanges. In toes 2-5, we have a proximal and a distal interphalangeal joint, and this occurs because these toes have three bones. With only two bones in the hallux, we only have an interphalangeal joint in our first toe.
- You should be able to identify whether or not each of these three bones come from the right or left side of the body. Knowing if a particular landmark is medial or lateral, anterior or posterior, you should quickly determine the side of the body the bone came from. For example, the lateral position of the greater trochanter of the femur and the subsequent position of the head of the femur should help you orient the bone as a right or left.
- Understanding these anterior/posterior and medial/lateral landmarks will also help you to quickly get your orientation and understand what structures you are looking at.
Activity 2: Radiology-Bones of the Lower Extremity
The most common way that you will see bones in the clinical setting is through radiology. Therefore, it is important for you to understand what normal bony anatomy looks like in radiological images. In this activity, you will use a radiology slideshow in Canvas to identify landmarks on the bones of the lower extremity. You will primarily examine x-ray images, but there will be a few MR and CT images as well.
Compare the landmarks on the skeleton to the radiological images along the way. This will help you to make sense of what you see in the images. You can also use an atlas to compare the bones with the radiology.
Wrap up and clinical connection
For today’s clinical connection, we will look at common bony injuries to the lower extremity. The first two videos are on a tibial plateau fracture that happened to a famous Badger athlete. There are following videos discussing stress injuries to bones of the lower extremity, including a femoral stress fracture, tibial stress syndrome (shin splints), and a metatarsal stress fracture. Watch the videos in the slide show and read the text for further knowledge about the bony injuries. The slide show is below and also posted in Canvas.