從生物力學的觀點來看，義足在足跟著地(heelstrike)的瞬間要扮演吸收震盪(shock absorption ) 的角色，緊接著要控制好足踝庶窟(p1antar flexion )的節奏，在站立中期(mid-stance phase) ，義足則要協助拉管小腿骨幹往前擺動(tibial advancement )的流暢性;進入足跟離地(heeloff)時，義足 前端必須能形成個堅硬的滾動軸心(rocker)，最後將整個身體之童心往前推進並轉移到對個腳去。義足可分為下列四大類:(1 )有踝關節的義足又稱為傳統型義足(conventional foot， CF) ，此型義足以j少奇義足(solid-ankle-cushion-heel，SACH foot)為代表;(2)有踝關節的義足，又分為單軸 ( single-axis foot)及多軸義足( multiple-axis foot)等兩種; (3 )儲存能量再釋放的義足(energy storing and return， ESAR foot) ; (4)生物科技動力足( bionic foot) ，運用氣壓式或電動式的人工肌肉驅動的義足。傳統的沙奇義足，以及軍軸或多軸等有踝關節義足，當初的設計只是為了能走路。1980年代風起雲湧的儲存能量再釋放義足，雖然頗受截肢患者的喜愛，但是至今仍沒有足夠的研 究證明它們可明顯節省能量支出。最近十多年，拜科技的進步，已有許多研究證明生物科技動力足一方面可以模仿人類足躁之動作，另一方面也確實可以節省患者之能量消耗。假以時日，生物科技動力足必將成為義足的明臣之星。(物理治療2011;而(4):299-304)

From the point of view in biomechanics， the prosthetic foot should mimic the function of the human foot throughout the gait cycle. During the initial contact， the prosthetic foot must absorb the impact of the heel contacting the ground and minimize the force that is transferred to the residual limb. During the loading response phase， the foot must provide control of plantar flexion. At midstance， the foot must provide controlled advancement of the tibia. During terminal stance， the foot must provide controlled heel rise and progression onto the forefoot， which becomes a rocker， rolling over and the tibia advances. ln general， prosthetic foot can be classified into four categories. These are conventional foot (CF)， single-axis/multiple-axis foot， energy“storing-and returning (ESR) foot and the recently so-called bionic foot.Early prosthetic feet were designed for walking only. Nowadays， it is strongly believed that new prosthetic feet concepts should be equipped with active components trying to mimic human ankle behaviour entirely. Most parts of the bionic foot are still on the research level but one can expect that they will become available on the market soon. (FJPT 2011 ;36(4):299-304)