Chapter 10
The Muscular System
In Chapters 7 and 8, you were
introduced to Kayla Tanner, a 45-year-
old mother of four who had suffered a
dislocated right hip in the bus accident
on Route 91. Six weeks after the injury, Mrs. Tanner reported that
she was still unable to walk or run without hip pain, and had
weakness in her hip, knee, and ankle. Mrs. Tanner walked with
a limp that her doctors attributed to weaknesses in flexion at the
knee, inversion of the foot, and plantar flexion.
Electromyography (which measures muscle electrical activity)
and nerve conduction studies (which measure the speed of nerve
impulses) revealed that Mrs. Tanner’s sciatic nerve had been
damaged as a result of her injuries—most likely as a result of the
nerve being compressed when the hip was dislocated. This large
nerve innervates a large number of lower limb muscles. Since her
surgery, Mrs. Tanner has been undergoing intense physical therapy
and has shown significant improvement.
During her initial visit with the physical therapist, Mrs. Tanner
presented with significant “foot drop” (the inability to dorsiflex
the foot when taking a step). Mrs. Tanner was asked to perform a
variety of movements with her right lower extremity. The therapist
focused her attention on the
prime movers
of the
hip, knee, and ankle. What are “prime movers” and “synergists”?
In order to assess the function and strength of a specific muscle, a
physical therapist will often apply resistance (push against the moving
limb) to mimic the action of an
antagonist muscle
. What is an
antagonist muscle, and why would the therapist mimic its action?
Mrs. Tanner’s physical therapist performed a variety of
assessments in order to establish a baseline from which her
recovery could be measured. For each of the descriptions below,
name the muscle (or muscles) that the therapist was assessing.
With Mrs. Tanner in the seated position, the therapist
positioned Mrs. Tanner’s legs shoulder-width apart, then
asked Mrs. Tanner to bring her feet together while the
therapist applied resistance to the right leg.
The therapist applied resistance to the top of Mrs. Tanner’s
foot and asked her to pull her forefoot up toward her shin.
With Mrs. Tanner in the prone position (on her stomach), the
therapist applied resistance to the leg while Mrs. Tanner was
instructed to bring her heel up toward her buttocks (flex her
Using descriptions similar to those listed in the question above,
explain how you would assess the function of the following
Extensor hallucis longus
Fibularis (peroneus) longus
(Answers in Appendix H)
Case Study
Muscular System
previous page 419 Human Anatomy and Physiology (9th ed ) 2012 read online next page 421 Human Anatomy and Physiology (9th ed ) 2012 read online Home Toggle text on/off