Chapter 2: Biomechanical Principles in Prosthetics and Orthotics

Multiple Choice
Identify the choice that best completes the statement or answers the question.

____	1.	A therapist examines a knee–ankle–foot orthosis with an articulating ankle joint. Which of the following correctly describes the desired location of the orthotic ankle joint with respect to the patient’s ankle?
a.	The medial joint is one-half inch posterior to the apex of the medial malleolus, and the lateral joint is one-half inch anterior to the apex of the lateral malleolus.	
b.	The medial joint is at the apex of the medial malleolus, and the lateral joint is at the apex of the lateral malleolus.	
c.	The mechanical (orthotic) ankle axis is parallel to the knee axis.	
d.	Only A and C are correct.	
e.	Only B and C are correct.	

____	2.	A therapist examines a knee–ankle–foot orthosis with an articulating knee joint. Which of the following correctly describes the desired location of the orthotic knee joint with respect to the patient’s knee?
a.	The medial knee joint is one-half inch anterior and superior to the medial epicondyle.	
b.	The lateral knee joint is midway between the anterior and posterior surfaces of the knee at the level of the knee joint line.	
c.	The orthotic knee axis is parallel to the ankle axis in the transverse plane.	
d.	None of the choices (A, B, C) are correct.	

____	3.	A patient wearing a transfemoral prosthesis has developed a hip flexion contracture after the prosthesis was fit and received by the patient. In static standing, this will most likely cause the line of gravity to produce an undesirable ____ on the prosthetic side.
a.	Hip flexion moment	
b.	Knee flexion moment	
c.	Knee extension moment	
d.	A and C	
e.	A and B	

____	4.	A patient has a flexible varus deformity at the ankle due to a muscle imbalance. A therapist selects an ankle–foot orthosis to minimize the unwanted varus using three-point counterforces. To be effective, the orthosis must provide a middle force that is directed ____.
a.	Lateral to medial	
b.	Medial to lateral	
c.	Anterior to posterior	
d.	Posterior to anterior	

____	5.	A therapist examines an ankle–foot orthosis that has componentry that stops dorsiflexion at 0° (neutral) and plantarflexion at 40°. The problem that this orthosis was most likely prescribed to improve is ____.
a.	Foot drop	
b.	Insufficient push-off	
c.	Insufficient knee flexion	
d.	Insufficient knee extension	

____	6.	A therapist examines a transfemoral prosthesis and notes that the prosthetic knee axis is located one-half inch posterior to a line connecting the locations of the greater trochanter and the ankle. This alignment enhances ____.
a.	Hip flexion	
b.	Hip extension	
c.	Knee flexion	
d.	Knee extension	
e.	Ankle plantarflexion	

____	7.	A therapist selects a temporary ankle–foot orthosis constructed from molded thermoplastic for a patient. When applied to the patient, the trimlines of the orthosis are located at the apexes of the medial and lateral malleoli. The therapist expects that this appliance will ____.
a.	Facilitate dynamic push-off	
b.	Facilitate dorsiflexion assist	
c.	Restrict plantarflexion and dorsiflexion movements	
d.	Only A and B	

____	8.	A spinal orthosis that employs a three-point counterforce system to restrict trunk flexion will include ____.
a.	An anterior to posterior middle force	
b.	A posterior to anterior middle force	
c.	End forces that are applied posteriorly	
d.	Only A and C	
e.	Only B and C	

____	9.	Which of the following strategies can be used to minimize knee hyperextension? Note: all the choices below are applied to the side of the hyperextension.
a.	Preventing plantarflexion beyond a position of 3° of dorsiflexion	
b.	Preventing dorsiflexion beyond a position of 3° of plantarflexion	
c.	Use of a small heel lift	
d.	Only A and C	
e.	Only B and C	

____	10.	In order to control a prosthesis of the identical type, an amputee with a shorter residual limb will need to produce ____ force as compared to an individual with a longer residual limb.
a.	More	
b.	Less	
c.	The same amount of	

____	11.	Biomechanical methods to reduce pressure between an appliance and its wearer include which of the following?
a.	Increase surface contact area between the wearer and the device.	
b.	Provide relief areas over pressure-sensitive areas and relief additions over pressure-tolerant areas.	
c.	Increase lever arm length of the applied forces.	
d.	Only A and B	
e.	Choices A, B, and C are correct.	

____	12.	In adults, who are aging typically, gait speed decreases with increasing age. This reduction in gait speed is most often associated with ____.
a.	A reduction in cadence, rather than a reduction in step length	
b.	A reduction in step length, rather than a reduction in cadence	
c.	Equal reductions in both cadence and step length	
d.	An increase in step width, which requires more time for lateral excursion of the center of mass	

____	13.	In orthotic and prosthetic applications, force couples ____.
a.	Are employed in four-point force systems to control movement of limb segments	
b.	Are composed of middle and end forces	
c.	Are the most common method employed by an ankle–foot orthosis to restrict foot drop	
d.	Are a biomechanical method of coupling orthotic control at the ankle to control movement at the knee without bracing across the knee	
e.	Only B and C are correct.	

____	14.	During the gait cycle, double limb support occurs when ____.
a.	One limb is in early midstance and the other is in late midstance	
b.	One limb is in early midstance and the other is in terminal stance	
c.	One limb is in preswing and the other is in loading response	
d.	One limb is in loading response and the other is in terminal stance	

____	15.	The typical gait speed in an unimpaired healthy adult is about ____.
a.	1.3 meters per second	
b.	2 to 3 miles per hour	
c.	3 to 4 meters per second	
d.	Both A and B are correct.	

____	16.	A therapist observes a patient walking between parallel bars with an asymmetric step length, right step shorter than left. The therapist correctly suspects that ____.
a.	The right leg is the involved leg	
b.	The left leg is the involved leg	
c.	The right stride is also shorter than the left stride	
d.	Choices A and C are correct.	
e.	Choices B and C are correct.	

____	17.	Select the statement that is true about gait speed.
a.	As walking speed increases, stance and swing time decrease equally.	
b.	As walking speed increases, stance time decreases and swing time increases.	
c.	As gait speed increases, running begins when the double support phases are eliminated.	
d.	As gait speed increases, running begins when swing time exceeds stance time.	

____	18.	The time in the gait cycle when all three lower limb joints (hip, knee, ankle) are moving in the same direction away from the ground is ____.
a.	Immediately after a heel strike initial contact	
b.	During midstance	
c.	Just after heel-off in preswing	
d.	During midswing	
e.	During late swing	

____	19.	Which of the following statements is false concerning typical joint movements of the swing leg during gait in an unimpaired healthy adult?
a.	The pelvis on the swing side rotates anteriorly.	
b.	The hip rotates medially.	
c.	The knee reaches maximum flexion during early swing.	
d.	The ankle is in a position around neutral.	

____	20.	During the gait cycle of a healthy unimpaired adult, maximal hip extension typically ____.
a.	Occurs during stance phase at the end of terminal stance	
b.	Is about 20 degrees	
c.	Occurs at about the time of contralateral initial contact	
d.	Occurs in conjunction with anterior pelvic tilt	
e.	All (A, B, C, D) correctly complete the sentence.	

____	21.	The majority of the force to produce knee flexion at the initiation of swing phase is produced by contraction of the ____.
a.	Hamstring muscles, hip flexor muscles, and plantarflexor muscles	
b.	Hip flexor muscles and hamstring muscles	
c.	Hamstring muscles	
d.	Hip flexor muscles and plantarflexor muscles	

____	22.	The support moment as described and defined by Winter ____.
a.	Is the sum of all sagittal plane external moments at the hip, knee, and ankle	
b.	Is composed of forces that push the body (trunk) away from the ground and collectively produce an extension moment	
c.	Include forces produced by the hip flexors, knee flexors, and dorsiflexors	
d.	All (A, B, C, D) correctly complete the sentence.	

____	23.	The muscle(s) that produce(s) the majority of the force that supports the body during midstance through the end of stance phase is/are ____.
a.	The hip extensor muscles	
b.	The hip extensor muscles and quadriceps	
c.	The quadriceps and gastrocnemius	
d.	The gastrocnemius	
e.	The hip extensor muscles and gastrocnemius	

____	24.	The comfortable or self-selected free walking speed used by most healthy individuals who wear a prosthetic or orthotic device to walk is ____.
a.	About the same as typical individuals of the same age, but it requires more energy expenditure	
b.	Slower than typical individuals of the same age, and it requires more energy expenditure	
c.	Slower than typical individuals of the same age, but it requires the same amount of energy expenditure	

____	25.	Following amputation of a limb segment, balance may be impaired in an individual without a neuromuscular disorder due to ____.
a.	A shift in the location of the center of mass	
b.	Loss of sensory input from the missing limb segment	
c.	Loss of joints and muscles that participate in the support strategies used to maintain or recover balance during perturbation	
d.	All (A, B, C) correctly complete the sentence.	

Chapter 2: Biomechanical Principles in Prosthetics and Orthotics
Answer Section

MULTIPLE CHOICE

	1.	ANS:	B	PTS:	1

	2.	ANS:	D	PTS:	1

	3.	ANS:	D	PTS:	1

	4.	ANS:	A	PTS:	1

	5.	ANS:	D	PTS:	1

	6.	ANS:	D	PTS:	1

	7.	ANS:	C	PTS:	1

	8.	ANS:	B	PTS:	1

	9.	ANS:	D	PTS:	1

	10.	ANS:	A	PTS:	1

	11.	ANS:	E	PTS:	1

	12.	ANS:	B	PTS:	1

	13.	ANS:	A	PTS:	1

	14.	ANS:	C	PTS:	1

	15.	ANS:	A	PTS:	1

	16.	ANS:	B	PTS:	1

	17.	ANS:	C	PTS:	1

	18.	ANS:	C	PTS:	1

	19.	ANS:	B	PTS:	1

	20.	ANS:	E	PTS:	1

	21.	ANS:	D	PTS:	1

	22.	ANS:	B	PTS:	1

	23.	ANS:	D	PTS:	1

	24.	ANS:	B	PTS:	1

	25.	ANS:	D	PTS:	1