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Chapter 9
Articulations
343
CASE STUDY
Bubba Brown, age 15, is a running back on his high-school football
team. Today during practice, he was running down the field when he
was tackled from the side at knee level. Bubba felt his knee “pop”
and was unable to walk off the field without assistance. Ice was applied to the injury and Bubba was evaluated by the team athletic
trainer, who elevated Bubba’s knee and found that the affected area
was not swollen. The athletic trainer did note, however, that there
was joint line tenderness on the medial side of the knee, limited flexion in the affected knee, and inability to completely extend the leg.
When asked to bear weight, Bubba’s injured knee “gave way on him.”
Bubba is referred to the orthopedist for evaluation and follow-up. The
orthopedist examines the knee and takes a series of radiographs and
an MRI. He then schedules Bubba for arthroscopic surgery. The
arthroscopy shows a tear in the medial meniscus. The surgeon repairs
the tear, and Bubba is placed in a hinged splint and begins a program
of rehabilitation with the sports medicine clinic.
2. Which of the following factors makes the knee joint more
vulnerable to injury as just described?
A.
B.
C.
D.
The
The
The
The
knee is relatively unprotected by muscle.
ligaments found here are very fragile.
knee is a weight-bearing joint.
knee cannot be pronated.
3. Why is Bubba unable to fully extend his leg on the affected
side?
A. He may have a mechanical obstruction from the displaced
meniscus.
B. Muscle spasm in the thigh may prevent full extension.
C. Joint effusion may prevent full extension.
D. All of the above.
1. Which of the following represents normal movement of the knee
joint?
1.
2.
3.
4.
Flexion
Extension
Supination
Hyperextension
A. 1 and 2
B. 1, 2, and 3
C. 2 and 4
D. 1, 3, and 4
CHAPTER SUMMARY
INTRODUCTION
A. Articulation—point of contact between bones
B. Joints are mostly very movable, but others are immovable or
allow only limited motion
C. Movable joints allow complex, highly coordinated, and purposeful movements to be executed
CLASSIFICATION OF JOINTS
A. Joints may be classified by using a structural or functional
scheme (Table 9-1)
1. Structural classification—joints are named according to
a. Type of connective tissue that joins bones together (fibrous or cartilaginous joints)
b. Presence of a fluid-filled joint capsule (synovial joint)
2. Functional classification—joints are named according to
the degree of movement allowed
a. Synarthroses—immovable joint
b. Amphiarthroses—slightly movable
c. Diarthroses—freely movable
B. Fibrous joints (synarthroses)—bones of joints fit together
closely, thereby allowing little or no movement (Figure 9-1)
1. Syndesmoses—joints in which ligaments connect two
bones
2. Sutures—found only in the skull; teethlike projections
from adjacent bones interlock with each other
3. Gomphoses—between the root of a tooth and the alveolar
process of the mandible or maxilla
C. Cartilaginous joints (amphiarthroses)—bones of joints are
joined together by hyaline cartilage or fibrocartilage; allow
very little motion (Figure 9-2)
1. Synchondroses—hyaline cartilage present between articulating bones
2. Symphyses—joints in which a pad or disk of fibrocartilage
connects two bones
D. Synovial joints (diarthroses)—freely movable joints (Figure 9-3)
1. Structures of synovial joints
a. Joint capsule—sleevelike casing around the ends of the
bones that binds them together
b. Synovial membrane—membrane that lines the joint
capsule and also secretes synovial fluid
c. Articular cartilage—hyaline cartilage covering the articular surfaces of bones
d. Joint cavity—small space between the articulating surfaces of the two bones of the joint
e. Menisci (articular disks)—pads of fibrocartilage located
between articulating bones