10: The Lower Limb

Chapter 10imageThe Lower Limb

The lower limb can be compared to the upper limb, bearing in mind that, during development, both limbs rotate 90 degrees in opposite directions. This results in the big toe ending up on the medial side, whereas its upper limb equivalent, the thumb, is on the radial side. The bones, joints, and musculature of the lower limb are relatively larger and sturdier because they are modified for weight bearing and mobility.

1 Skeleton

THIGH

Femur

Description

The femur is the only bone of the thigh (Figure 10-2). It is a large, long bone with a rounded head superiorly that articulates with the os coxae and two large knuckles, or condyles, that articulate inferiorly with the tibia.

Features

Patella

The patella is a sesamoid bone embedded within the tendon of the quadriceps femoris muscle (Figure 10-3). The anterior surface is roughened for the tendinous attachments to the quadriceps femoris muscle. The medial and lateral borders converge inferiorly as the apex. The posterior aspect of the patella is lined with articular cartilage that articulates with the trochlea of the femur. The articular surface is divided into several facets.

LEG

There are two long bones of the leg, the tibia on the medial aspect and the fibula on the lateral.

ANKLE AND FOOT

Tarsal Bones

The tarsal bones in the ankle correspond to the carpal bones of the wrist, but there are seven tarsals in the ankle compared to eight carpals in the wrist (Figure 10-5). The tarsals occupy the posterior half of the foot. Two tarsals, the talus and calcaneus, are considerably larger, weight-bearing bones and comprise the entire posterior aspect of the foot.

2 Joints

HIP JOINT

Features

The hip joint is an extremely stable yet moveable ball-and-socket joint (Figure 10-7). It is an articulation between the spherical head of the femur (ball) and the cup-shaped acetabulum of the os coxae (socket). The articular surface of the acetabulum is horseshoe-shaped. The concavity of the acetabulum is further deepened by the acetabular labrum, a fibrocartilage ring that encircles the rim of the fossa. A joint capsule surrounds the joint, affording it a fair degree of movement. The capsule is thickened and reinforced by three strong ligaments running from each component of the os coxae to the neck of the femur to prevent dislocation of the joint. The ligaments include the iliofemoral ligament anteriorly, the ischiofemoral ligament posteriorly, and the pubofemoral ligament inferiorly and anteriorly. The ligament of the head of the femur is a rather weak ligament that runs from the lower end of the acetabulum to the fovea on the head of the femur. It may contain a small nutrient artery to the head of the femur.

Movements

The following movements are described in relation to the anatomical position (Figure 10-8). This assumes that the foot is moved from the ground with resultant movement of the femur at the hip. If the foot remains on the ground, however, the os coxae moves in relation to the femur. The hip joint is capable of six movements:

Circumduction is a combination of flexion, extension, abduction, and adduction in a wide conical arc about the hip.

THE KNEE JOINT

The knee joint is the largest and perhaps the most complicated joint in the body (Figure 10-9). It is classified as a synovial joint with interposing fibrocartilage discs, or menisci. The knee is really a complex of three joints: (1) between the lateral condyles of the femur and tibia, (2) between the medial condyles of the femur and the tibia, and (3) between the patella and the femur. The joints between the tibia and femur represent the weight-bearing portion of the knee. They are moveable, synovial joints that allow a combined hinge and sliding type movement and limited rotation. The joint between the patella and the femur allows a sliding type of movement.

The knee is susceptible to injuries that are work- and sports-related. In addition, genetic factors and the aging process may result in degenerative joint disease (primary osteoarthritis).

Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 10: The Lower Limb
Premium Wordpress Themes by UFO Themes