A 58-year-old man who underwent a transfemoral amputation complains that walking with his prosthesis exhausts him far more than before surgery, whereas his friend with a transtibial amputation manages well. The main reason for the higher metabolic cost of walking in a transfemoral amputee is:
- A The prosthetic socket causes chronic venous obstruction in the residual limb
- B Loss of the anatomical knee joint forces compensatory hip musculature use and eliminates normal knee-controlled swing ✓
- C Transtibial amputees always receive energy-storing feet while transfemoral amputees do not
- D Transfemoral amputees have obligatory cardiac deconditioning from surgery
Correct answer: B. Loss of the anatomical knee joint forces compensatory hip musculature use and eliminates normal knee-controlled swing
Explanation
Oxygen consumption during walking rises roughly 10 to 40 percent above normal in transtibial amputees but about 50 to 70 percent in transfemoral amputees. The dominant reason is loss of the anatomical knee: the amputee must control the prosthetic knee with hip extensors and abductors, loses normal swing-phase mechanics, and adopts a slower, wider, more effortful gait. Socket venous obstruction and cardiac deconditioning are not established mechanisms.
Reference: Campbell's Operative Orthopaedics, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.