Download or read book Design and Testing of a Variable Stiffness Transverse Plane Adaptor for Use in a Lower Limb Prosthesis written by Corey Pew and published by . This book was released on 2014 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of a lower limb prosthesis is to restore the abilities of the intact limb for an amputee. Daily ambulation includes many maneuvers such as turning, pivoting, and uncertain terrain, all of which require a component of transverse plane mobility. It has been shown that the addition of a transverse plane adaptor can help to decrease soft tissue damage, increase mobility, and help reduce the risk of falls in amputees. However, currently available transverse plane adaptors only allow for a single stiffness setting and do not allow for variation to accommodate the maneuvers of everyday ambulation. The aim of this research was to design, build, and test a prototype lower limb prosthetic adaptor that is capable of variable stiffness in the transverse plane. The device will be used to better understand the role transverse stiffness plays in varying daily ambulation activities such as walking and turning. A variable stiffness torsion device (VSTA) was designed, and built and is capable of controlling stiffness in the transverse plane of a lower limb prosthesis. Design criteria were established to determine structural and functional requirements for the VSTA. A custom spring was designed with a rate of 0.33 Nm/?? allowing for VSTA settings between 0.10-1.17 Nm/°, and includes a locked infinitely stiff setting. Refinement of the design was then conducted using a mathematical model, finite element analysis (FEA), and analysis of VSTA kinematics. Following design completion, a prototype was built and tested. boldMechanical Testing Mechanical bench testing was performed to determine the physical capabilities of the VSTA. The VSTA is actually capable of infinite stiffness variation between 0.12-0.91 Nm/°. Initial designs accounted for the internal spring to be capable of 90° of deflection which would have allowed for infinite stiffness variation between the minimum and infinitely stiff, however, internal spring stresses limited spring deflection to 57°, resulting in the limited range of the VSTA. The bench testing showed that the VSTA as designed and manufactured would be suitable for human subjects testing. A proportional-integral-derivative (PID) controller, provided by the motor manufacturer, was used to control step inputs of the spring carrier to adjust the stiffness of the VSTA. The controller, using a 16 volt supply, could accurately perform step inputs, but could not meet rate of performance design goals. When supply voltage was brought up to the ideal 24 volts the controller was able to meet the rate goals of the VSTA, however, over power faults occurred resulting in incomplete step controls. Use of a different control module that would allow for the full 24 volt supply to the motor and with consideration of the reduced functional range of the VSTA it is estimated that the controller would meet all design goals. Structurally the VSTA needs to be improved beyond the factor of safety of one to provide a more robust solution. Mechanical improvements include increasing VSTA ability to apply and sustain higher stiffness settings without being limited by overstress of the spring. It would also be beneficial to test the VSTA for use as an active stiffness generator, modulating stiffness while under load. Additionally, the controller could be developed to better optimize the gains, and possibly increase speed and performance of the system. Lastly, human subjects testing should be conducted to better evaluate the VSTA's ability to function in a real setting, as well as to better understand the role of transverse plane stiffness during ambulation.

Download or read book Testing and Advancement of a Variable Stiffness Transverse Plane Adapter for Use in a Lower Limb Prosthesis written by Corey Pew and published by . This book was released on 2017 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: At each activity-speed combination subjects compared stiffness settings and indicated their preference for one of three settings (Compliant: A (0.31 Nm/deg), Moderate: B (0.83 Nm/deg), Stiff: C (1.29 Nm/deg). Results indicated correlation between increased peak transverse plane moment with increasing walking speed when turning, but not when walking straight. However, contrary to the outcome of previous findings, no significant relation was found between peak transverse plane moment and the stiffness of the VSTA II. Lastly, results indicated no significant trend for stiffness preference between speeds or activities, while subjects did qualitatively prefer lower stiffness when turning vs straight walking. Findings may indicate that no global ideal stiffness settings may be available given activity and speeds variations, but that VSTA II settings may have to be tailored to individual users. Conclusions Testing with the VSTA I and VSTA II prototypes identified that reduced transverse plane stiffness in the shank of a lower limb prosthesis can significantly reduce peak loading on the residual limb. Moreover, that transverse plane stiffness could be reduced beyond what is available in current, single stiffness, transverse rotation adapters. Reductions in stiffness also have no effect on the user’s mobility when walking at their self-selected speed. Initial attempts were made to determine a global control scheme that could indicate when and to what level stiffness should be adjusted, however, no overall trend could be found. It was determined that reduced transverse plane stiffness produces the most significant reductions in limb loading when turning compared to straight walking. Additionally, walking speed played a significant role in transverse plane limb loading such that both factors should be considered when determining the optimal transverse plane stiffness for a given activity and speed combination. Overall a control scheme that optimizes when and to what level to adjust transverse plane stiffness should be customized to an individual’s specific needs and preferences.

Download or read book Foot and Ankle Biomechanics written by William Ledoux and published by Academic Press. This book was released on 2022-12-05 with total page 815 pages. Available in PDF, EPUB and Kindle. Book excerpt: Foot and Ankle Biomechanics is a one source, comprehensive and modern reference regarding foot and ankle biomechanics. This text serves as both a master reference for foot biomechanics, presenting a clear state of the research and capabilities in the field. The customers for this book will be those looking for information on foot and ankle biomechanics for a range of applications; for example, designers of orthotics. - Provides a comprehensive overview of the science of foot and ankle biomechanics that is presented in an easily accessible format - Presents normative data and descriptions relating to the structure and function of the foot and ankle, along with comparisons to pathological conditions - Includes multimedia content to support modeling and simulation chapters

Download or read book Reducing Socket Discomfort and Torsional Stresses for Individuals with Lower limb Amputation Using a Novel Prosthesis written by Connor William Mulcahy and published by . This book was released on 2021 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Individuals with lower-limb amputation often suffer pain and discomfort at the socket-residual limb interface after using their prosthesis. A portion of this pain and discomfort can be isolated to the transverse plane. It has been shown that the inherent geometry of the bones in the ankle joint produce motion in the transverse plane; however, prosthetic limbs generally only function in the sagittal plane. Torsion adapters are a clinical product used to passively allow rotation in the transverse plane at the pylon level of a prosthesis. These adapters have been shown to relieve skin problems, but they introduce a perceived decrease in stability. Olson made a first iteration Torsionally Active Prosthesis (TAP) in a pilot study which showed that a powered prosthesis operating in the transverse plane can reduce transverse socket torque. The study presented in this thesis continued Olson’s preliminary work by iterating on the TAP’s design and testing more human subjects. By coupling sagittal plane rotation with transverse plane rotation, this study hypothesizes that there exists a coupling ratio (CR) that minimizes peak transverse-plane socket torque and maximizes user satisfaction. Participants (n=3) tested the TAP under a range of CRs for three different walking regimes: straight walking, prosthesis inside circle walking, and prosthesis outside circle walking. Initial results suggest a small CR will minimize socket torque within each walking regime. For straight walking, a small or zero CR may minimize socket torque. For circle walking, a small, nonzero CR may also minimize socket torque independent of whether the prosthesis is on the inside or outside limb. Initial results for comfort level showed that changing CRs did not present any trends. Further human subject tests with the TAP are warranted because increasing the comfort level and residual limb health of users is of significant clinical interest.

Download or read book Transverse plane Ankle Rotation for Lower limb Amputees Using Two Novel Prostheses written by Nathan M. Olson and published by . This book was released on 2016 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lower-limb amputees often suffer from pain and discomfort caused by prosthesis use. Problems include musculoskeletal issues caused by compensatory gait patterns and skin injuries caused by shear stress at the interface between the residual limb and the socket. Torsion adapters have been shown to relieve these skin problems, but are not commonly prescribed due to a perceived decrease in stability. This study describes the Torsionally Active Prosthesis (TAP), a novel prosthesis that aims to provide the same reduction in shear stress as a torsion adapter without the accompanying decrease in stability. The work consists of four parts. First, a powered prosthesis capable of general motion in the transverse plane was developed. Second, exploratory human subject testing was performed to identify a pattern of motion that reduces transverse-plane torque at the socket without reducing torsional stiffness. The results indicate that this can be achieved by coupling transverse-plane ankle rotation with sagittal-plane ankle rotation. Third, the powered prosthesis was configured to perform this axis coupling and human subject testing was performed to determine its efficacy. Three subjects wore the prosthesis and walked at their self-selected speed in straight lines and clockwise and counterclockwise circles with at least three levels of axis coupling, including zero coupling. The subjects showed a trend toward decreased socket torque with increased axis coupling. Finally, the Pivot-Flex Foot (PFF), an unpowered prosthesis that could provide axis coupling was designed, built, and bench-tested. The PFF demonstrated a linear coupling between transverse-plane ankle rotation and sagittal-plane ankle rotation during bench testing.

Download or read book Design and Evaluation of a Quasi passive Variable Stiffness Ankle foot Prosthesis to Improve Biomechanics Across Walking Speeds written by Emily Rogers-Bradley and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Currently there are an estimated 875,000 people with major lower limb loss in the United States, with numbers projected to increase 1.6-fold by 2050 due to increasing prevalence of diabetes, obesity, and related dysvascular conditions [1]. Lower limb amputation often leads to secondary conditions such as knee pain, knee osteoarthritis, osteopenia, back pain, postural changes, and general deconditioning [2]. For people with transtibial (below-knee) amputation, prevalence of knee osteoarthritis in the contralateral limb is 17x higher than in the general population, with 27% of people with unilateral amputation developing knee osteoarthritis [3]. This large increase in incidence is likely due to insufficient push-off power from the prosthesis and increased limb loading on the contralateral side [4]. This thesis presents an ankle-foot prosthesis which increases energy storage and return, increases peak power, and decreases contralateral limb loading in a low-mass, quasi-passive device. This is achieved by automatically adjusting prosthesis stiffness to maximize energy storage across walking speeds. A novel quasi-passive variable stiffness ankle-foot prosthesis is presented with high resolution stiffness adjustment from 352 - 479 Nm/radian, corresponding to biological ankle quasi-stiffness during level ground walking from 0.75 - 1.5 m/s for a 50th percentile male. This thesis presents the development of a novel mechanism for varying bending stiffness of leaf springs which utilizes independently controlled lockable linear actuators which constrain relative sliding of parallel leaf springs relative to a mechanical ground to control bending stiffness. The detailed device design and analysis of the variable stiffness ankle-foot prosthesis is described, including a parametric model for approximating device stiffness, contact stress analysis, fatigue life calculations, and bolted joint analysis. The benchtop testing results demonstrate that the device successfully achieves the targeted stiffness range, device mass, and structural integrity. A study was conducted with 7 participants with unilateral transtibial amputation in order to evaluate the kinetic and kinematic effects of the variable stiffness prosthesis during walking compared to a passive energy storage and return foot. During the experiment, subjects walked on an instrumented treadmill at the speeds of 0.75 m/s, 1.0 m/s, 1.25 m/s, and 1.5 m/s while force and motion data was recorded. This thesis presents results from the clinical study which demonstrate a 15.5 - 19.3% greater peak ankle angle during walking across all speeds with the variable stiffness ankle compared to a passive control, 5.4 - 14.8% greater peak joint power, 10.5 - 23.7% greater energy return, and a 4.0 - 6.7% lower contralateral limb knee external adduction moment across walking speeds. This thesis presents the first of its architecture variable stiffness ankle-foot prosthesis utilizing a novel locking parallel leaf spring mechanism for stiffness control. The prosthesis has a lower device mass compared to existing powered and quasi-passive devices, and increases biomimetic functionality beyond standard passive prostheses. This thesis presents significant clinical results demonstrating the benefits of such a device on the biomechanics and energetics of people with transtibial amputation while walking. This device has the potential to improve health outcomes in people with transtibial amputation by normalizing biomechanics and increasing energy storage and return, and decreasing contralateral limb loading and unwanted knee external adduction moment. This prosthesis has the potential to expand access to high performance prosthesis technology by creating a device that is low mass, low power, and lower cost compared to fully powered devices.

Download or read book Controlled Coronal Stiffness Prosthetic Ankle for Improving Balance on Uneven Terrain written by Jeffrey J. Gorges and published by . This book was released on 2013 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: For lower limb amputees, quality of life is directly related to the functionality of their prosthetic devices. Uneven terrain can cause significant disturbances to an individual's gait. Disturbances with significant inversion or eversion are more likely to cause imbalance than sagittal plane disturbances, yet currently marketed devices do not have controlled methods for reacting in the coronal plane. The objective of this project was to develop a prosthetic ankle that is capable of changing stiffness characteristics in the coronal plane with the objective of creating a more stable support for amputees. This device will be used in further research to characterize kinematics in the coronal plane and develop strategies of improving amputee balance while traversing uneven terrain. Methods A prosthetic ankle was designed, built and tested that is capable of controlling the rotational stiffness of the ankle for inversion and eversion. The effective length of two cantilever beam springs can be changed by a motor controlled through a battery powered on-board computer. A series of bench tests and human subject tests were performed to test the functionality of the device including stiffness characterization, comparison to available commercial devices, motor control characteristics, human subject standing balance center of pressure tracking, and walking on an inverted and everted plane. Characterization of the device and stiffness properties showed that over a series of springs it was capable of developing a range of rotational stiffness values from 23 Nm/rad to 510 Nm/rad. When placed in series with a stiff commercial foot, one particular set of springs proved to have a greater range of stiffness than that covered by a series of commercial feet. Human subject testing demonstrated methods and metrics that could be used to evaluate optimal stiffness values and profiles. Motor tests showed that the drive system did not perform well enough to quickly change stiffness values while fully weighted on an inverted or everted surface.The range of stiffness characteristics over which the device is capable has proven to be sufficient. However, the drive system for dynamically changing the stiffness throughout the gait cycle requires a few design changes. The device has proven to be capable of testing the effects of amputee balance and kinematics while walking on uneven terrain. Further use of this device for research will help to develop the optimal coronal stiffness characteristics and controls for improved prosthetic ankles.

Download or read book External Limb Prostheses and External Orthoses Requirements and Test Methods written by British Standards Institute Staff and published by . This book was released on 1999-06-01 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prosthetic devices, Artificial limbs, Orthopaedic equipment, Orthopaedics, Prosthesis, Performance testing, Performance, Strength of materials, Electrical safety, Design, Ergonomics, Mechanical properties of materials, Mechanical testing, Instructions for use, Packaging, Testing conditions, Test equipment, Electromagnetic compatibility, Bend testing, Tensile testing, Stiffness, Specimen preparation, Fire tests, Combustion products, Toxicity, Control devices, Formulae (mathematics), Force measurement, Angular measurement, Vibration, Reports

Download or read book Biomechanics of Lower Limb Prosthetics written by Mark R. Pitkin and published by Springer. This book was released on 2009-10-14 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: Foreword from a Clinical Biomechanist, Applied Physiologist and Prosthetist teaching graduate students in Prosthetics & Orthotics. While there are many books on Biomechanics, arguably the quintessential science of limb prosthetics, none addresses the fundamental principles in sufficient detail and depth to be practically useful to the prosthetist, rehabilitation specialist or researcher. Dr. Pitkin’s monograph is an exemplary collection of theoretical principles from his research and o- ers, presented in its clinical and applied biomechanics form. The textbook provides an excellent overview of the many facets of lower limb prosthetic design and engineering for the ardent clinician researcher and student. The book delves into many of the basic concepts that are required knowledge for the clinician and the scientist to have as the foundation for their work. Dr. Pitkin has an e- quent manner in which he reflects on the history and literature to tell the storied evolution of prosthetic design . He takes the reader on a journey to consider his theories, which have substantive foundations to contemplate. By the end of chapter one, we have the basic h- tory and an appreciation for the rationale behind the “rolling joint ankle” with evidence to support his theoretical views.

Download or read book Development and Application of Semi active Prosthetic Foot ankle Systems written by Kieran Kieran Nichols and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a need for improved design and function of prosthetic devices to aid walking in persons with transtibial amputations. This dissertation focused on two semi-active ankle-foot prosthetic devices, the Variable Stiffness Foot (VSF) and Two Axis aDaptable Ankle (TADA), which allow users to change biomechanical ankle-foot functions using simpler designs, lower costs, and less power than active prostheses. The background for this dissertation explored the main lower-limb biomechanical principles of prosthetic design, prosthetic-walking mechanics, and sensor feedback. The VSF manuscript investigated the mechanical impact of adjusting stiffness on lower limb mechanics using a prosthetic foot, which can modulate forefoot stiffness. A less stiff VSF resulted in increased ankle dorsiflexion angle, decreased ankle plantarflexor moment, decreased knee extension, decreased knee flexor moment, and increased magnitudes of prosthetic energy storage, energy return, and push-off power. These findings suggest that a less stiff VSF may offer advantages in lower joint moments and greater ankle angle range of motion for individuals with lower-limb prostheses. The Two Axis aDaptable Ankle (TADA) is a semi-active prosthetic ankle that offers independent modulation of sagittal and frontal ankle angles. The first TADA study modified a Raspberry Pi 4 for real-time control of brushless direct-current motors, allowing for precise and reliable ankle angle adjustments. The control system employed CANopen over EtherCAT (CoE) for synchronized communication between the Raspberry Pi and motor controllers. The results demonstrated improved movement times, lower movement errors, and higher data transmission rates. As a continuation, the final TADA study aimed to create an ankle prosthesis that can synchronously record lower-body kinematics and kinetics and assess the sensitivity of those mechanics to different walking speeds and ankle angles for an unimpaired participant. Using a pylon load cell, the results showed that peak magnitudes and impulses increased for plantarflexor moments with increased plantarflexion angle and for evertor moments with increased inversion angles. Moreover, the peak sagittal pylon moments increased with higher walking speeds. The integrated control system of the TADA effectively controls ankle angles, can affect lower-body mechanical outcomes, and can allow for efficient adaptation to various speeds and terrains in users with transtibial amputations.

Download or read book Design and Testing of an Ankle foot Prosthesis and a Hip Exoskeleton to Improve Balance related Outcomes and Prevent Falls written by Vincent Louie Chiu and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Falling is a serious issue that affects millions of people, including people with lower limb amputation and older adults. Falls can lead to serious injury or death, and even the fear of falling results in restrictions on mobility and reductions in quality of life. Assistive devices could address this need by augmenting the three primary strategies humans use to maintain balance: applying ankle torque to modulate center of pressure and pushoff work, using hip torque to change center of mass position and velocity, and placing the foot to alter base of support. In my doctoral research, I have designed and tested devices intended to assist people with these three balance strategies. First, I designed a prosthetic foot with actuation in the frontal and sagittal planes, which is capable of modulating the center of pressure between the foot and the ground. I then used this foot to test the biomechanical effects of a prosthesis controller designed to mitigate the effects of uneven terrain. Finally, I designed a bilateral hip exoskeleton with actuation in the frontal and sagittal planes, which can be used to modulate hip torques and assist with foot placement. These projects have led to a better understanding of the relative efficacy of different balance enhancement techniques and have yielded new experimental tools for future studies of fall prevention.

Download or read book Design of a Novel Mechatronic System to Test Prosthetic Feet Under Specific Walking Activity Loads and Evaluate Their Lower Leg Trajectory Error written by Heidi V. Peterson and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lower limb amputees, numbered at more than 40 million globally, are challenged with limited mobility due to prosthetic devices that do not fully restore the functionalities of their biological limbs. While commercially available energy storage and return feet do restore some of the functionalities of a missing limb, the development and use of these prosthetic devices are limited by the current design, evaluation, and prescription processes. This is because the connection between the combined mechanical characteristics of a foot and user outcomes, such as mobility, comfort, and walking effort, is not fully understood. The lower leg trajectory error (LLTE) is a novel prosthetic foot performance metric that provides a quantitative connection between the mechanical characteristics of a foot and the expected gait of an amputee. Thus far, the LLTE value of a foot has only been calculated via simulation, which limits the practical use of the metric in prosthetic foot design, evaluation, and prescription. One way to systematically measure the LLTE value of a physical prosthetic foot would be through a mechanical bench test, but the capabilities of existing bench testing devices are insufficient due to limited degrees of actuation and reported accuracy. The purpose of this work was to design the Prosthetic Foot Testing Device (PFTD), a mechatronic testing device that could apply specific and uncoupled GRFs to any CoP on a foot and measure its deflection, through which it could measure the LLTE value and thus predict walking performance of any passive prosthetic foot. First, we determined high-level functional requirements of the PFTD, including the ranges of reference loads and prosthetic foot deflections as well as the LLTE measurement accuracy, such that the PFTD could meaningfully measure the full range of commercially available prosthetic feet. Second, we derived the relationships between the variables used to calculate the LLTE metric and those controlled or measured by the PFTD. Third, we used these relationships to design the PFTD and perform sensitivity analysis to ensure it could meaningfully and accurately measure the LLTE value of any passive prosthetic foot. In future work, the PFTD will be built, validated, and used to measure and compare the LLTE values of various prosthetic feet. The PFTD and theory presented herein may become a new tool in the prosthetics industry to systematically and amputee-independently measure and compare the performance of prosthetic devices using the LLTE value as a universal metric, which could ultimately improve the development and prescription processes of prostheses.

Download or read book Prosthetics Structural Testing of Lower limb Prostheses written by International Organization for Standardization and published by . This book was released on 2016 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Construction of a Variable Stiffness Prosthetic Arm Prototype microform written by Megan Catherine McTavish and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2005 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Variable Stiffness Prosthetic Leg for Transtibial Amputees written by Ian D. Hardey and published by . This book was released on 2010 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Powered Transtibial Prosthetic Device Control System Design Implementation and Testing written by Jinming Sun and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A powered lower limb prosthesis, which consists of a four bar mechanism, a torsional spring and a brushed DC motor, was previously designed and fabricated. To regulate the motor power input, a two level controller was proposed and built. The control algorithm includes a higher level finite state controller and lower level PID controllers. To implement the control system, a digital signal processor (DSP) control board and MATLAB Simulink were used to realize the higher level control and a DC motor controller was used to realize the lower level PID control. Sensors were selected to provide the required feedback. The entire control system was implemented on a convenient to carry backpack. Amputee subject testing was performed to obtain some experimental verification of the design. The results showed that the control system performed consistently with the designed control algorithm and did assist in the amputee{u2019}s walking. Compared to a currently available powered prosthesis, this control is simple in structure and able to mimic the nonlinear behavior of the ankle closely.

Download or read book Design of an Ankle Prosthesis for Two degree of freedom Motion in the Sagittal and Coronal Planes written by Colin Elley and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to get up and walk from one place to another under one's own power epitomizes a level of independence and the perception of a good quality of life. Loss of this ability can directly affect one's level of physical fitness and thus critically affect health and well-being. This ability to independently walk can be lost due to many causes including lower leg amputation. This leads to the need for an ankle prosthesis to aid the user in performing gait. Most current commercial ankle prostheses available for below-knee amputees allow for (limited) dorsiflexion and plantarflexion at the ankle. Therefore, the primary objective of this project was to develop an ankle prosthesis which can passively accommodate two degrees of freedom: motion in the sagittal plane (dorsiflexion and plantarflexion) and motion in the coronal plane (inversion and eversion). Two design iterations were done to accomplish this goal. The second design or Design 2 utilizes three torsion springs to passively allow for bi-planar motion in the sagittal and coronal planes. The range of motion for the ankle prosthesis was based on the range of motion of the ankle during normal gait and also accounts for the maximum grade and cross-slope of rural local streets. The Design 2 ankle prosthesis offers slight variability for motion in the sagittal plane by varying the stiffness of the ankle prosthesis for dorsiflexion and plantarflexion. With the exception of the latter part of the pre-swing phase, the theoretical behavior of the ankle prosthesis qualitatively replicates that of natural ankle motion in the sagittal plane found in literature. It also provides sufficient lateral stability during normal gait. The ankle prosthesis which was designed for this project can passively accommodate motion in both the sagittal and coronal planes as well as provide some degree of "push-off" during normal gait.