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At the end of this chapter, all students are expected to:

  1. Describe the goals of prosthetic and orthotic devices.

  2. Describe the types of forces applied by prosthetic and orthotic devices.

  3. Describe the gait cycle and the phases of gait.

  4. Describe the distance and temporal characteristics of gait.

  5. Describe the typical changes in gait that are associated with aging.

  6. Discuss the biomechanical effects of limb loss and use of a prosthetic or orthotic device on balance.

Physical Therapy students are expected to:

  1. Explain the biomechanical methods by which prosthetic and orthotic devices accomplish their goals.

  2. Discuss the biomechanical issues of the interface between the device and the user's anatomy.

  3. Discuss the kinematics and kinetics of gait, including internal and external moments during each phase of gait.

  4. Discuss muscle activity and function during gait.


Harry Green is a 67-year-old African American widow who suffered a thrombotic cerebral vascular accident (stroke) with right hemiparesis 3 weeks ago. Although he has type 2 diabetes (without peripheral neuropathy) and hypertension, he is medically stable with his current medications. Prior to his stroke, Mr. Green lived independently and was active at home and in the community. He is an inpatient in a rehabilitation hospital. Although sensation, cognition, and communication are intact, he has moderate weakness in both his right upper and lower extremities, with the greater weakness distally. He also has difficulty dissociating volitional movements in his right extremities; thus, when he tries to flex his right hip, he is compelled to flex all three joints in the extremity in the same direction at the same time. For example, when he walks, taking a step on the right is difficult because when he flexes his right hip to take a step, he is unable to extend his knee. He is, however, able to walk with assistance using a four-point cane, but his gait is slow, inefficient, and not always safe. He has little voluntary muscle activity in the right foot and ankle, which produces a right foot drop during gait, making right step initiation and swing more difficult. He exhibits varus positioning of his right ankle at initial foot contact as well as knee instability during right stance phase. For example, sometimes his right knee buckles causing balance difficulty, although he has had no falls to date. In his upper extremity, he has some voluntary muscle activity, which is greater in flexor muscles than extensors. He has some voluntary grasp and release in his right hand and can hold onto an object if placed in his hand. Using his upper extremity requires much effort and he does not use it functionally at present.

Case Study Activities

All Students:

  1. Identify and discuss Mr. Green's gait abnormalities and provide biomechanical explanations for his loss of balance and potential for falls.

  2. Discuss how Mr. Green's age may affect his gait and interact with his newly acquired ...

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