Devices will vary. Data gathered will form a baseline.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking distance measured by the 10 Meter Walk Test (10MWT). 10MWT improvement was defined as a minimum increase of 0.1 m/s.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking time measured in the L-Test. L-Test improvement was defined as a minimum decrease of 4.5 seconds.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking time measured in theRamp Test. Ramp Test improvement was defined as a minimum decrease of 6 seconds to complete the test.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in abulatory activities measured by the Activities-specific Balance Confidence Scale. Improvement in the ABC was defined as a minimum detectable change of 13% increase in score.

The ABC Scale is a self-administered questionnaire that asks the patient to rate his or her confidence in performing various ambulatory activities on a scale from 0% (no confidence) to 100% (complete confidence) without losing balance or becoming unsteady. Scores for each of the 16 items will be collected and an average percentage calculated, with scores <67 indicating an increased risk of falling.

The Falls Efficacy Scale is a validated 10-item self-report questionnaire designed to assess confidence in the ability to perform 10 activities of daily living without falling as an indicator of how one's fear of falling impacts physical performance. Each item is rated from 1 ("very confident") to 10 ("not confident at all"), and the per item ratings are added to generate a summary total score (10 to 100). Lower scores indicate more confidence and higher scores indicate lack of confidence and greater fear of falling. It has been validated for use in the elderly and persons with amputations. Scores ≥70 indicate an increased fear of falling. Improvement in the Falls Efficiacy Scale was defined as a minimum increase of 2 in the score.

The AMP is an instrument designed to measure ambulatory potential of lower-limb amputees. Subjects begin the test seated in a hard chair with arms and are tested for a total of 21 items assessing abilities of increasing level of difficulty. Abilities assessed include sitting balance, transfer from chair to chair, standing balance, gait quality, negotiating obstacles, and the use of assistive devices. The total score range for the AMP is 0 to 47 points. A minimal detectable change of 4 points was the definition of improvement.

The PLUS-M is a valid and reliable self-reported measure for the mobility of adults with lower limb amputations. PLUS-M asks about the patient's ability to perform simple and complex tasks. High PLUS-M scores correspond with greater mobility. Improvement in the Mobility PLUS-M (12 item Short Form) was defined by a minimum detectable change of an increase of 5 points in the total score.

The PSFS is a self-report, goal-attainment measure aimed at identifying functional status limitations that are most relevant to individual patients. The PSFS is a reliable, valid, and efficient measure for detecting clinical change in persons with low back pain and knee dysfunction. Subjects were asked to identify three to five activities that they are having difficulty or are unable to perform because of their injury/condition. For the specified activities, patients were asked to rate their ability to perform each activity at that time (0-10 numerical scale) with '0' being unable to perform the activity, and '10' being able to perform the activity at the same level as they could prior to the injury/condition. The total score was calculated as the sum of the activity scores divided by the number of activities. Changes of >2 in the total score compared to baseline were considered "Improved."

The NPRS is a valid and reliable measure of pain that may be used across all musculoskeletal injuries/conditions and complements the PSFS. The patient was asked to rate the pain of their joints, foot, lower back, and if they are using an assistive device any additional affected limbs on average over the last 24 hours on a scale 1-10, with '1' being 'very mild' and '10' being the 'unimaginable unspeakable'. The scores on the NPRS instruments with the emPOWER Ankle were compared to the scores on the subject's passive prosthesis. An improvement was considered a positive change of 1 for at least one area without a corresponding decrease in another.

A Fitbit activity monitor was worn to record the number of steps the Subject took with the prosthesis. The patient returned to the site with the activity monitor and the steps counted were downloaded from the device. In addition, the Subjects were sent home with a prepaid envelope and instructed to mail back the activity monitor if the next visit was more than 3 weeks later, to ensure that the data was not lost. The step counts were downloaded from the device the day the activity monitor was returned to the Investigator. The Investigator recorded the date the patient was affixed with the activity monitor, the date they received the returned activity monitor, and the date they synced the monitor. An improvement was defined as an increase in the average daily step count of 750 steps.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Physical Function improvement was defined as a minimally clinically important difference (MCID) of an increase of 6.8 in a total score.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Global Health Short Form improvement was defined as an increase in a total score of 3.5.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Fatigue Short Form (7a) improvement was defined as a minimally clinically important difference (MCID) of an increase of 5 in a total score.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Pain Intensity Short Form (3a) improvement was defined as a minimally clinically important difference (MCID) of an increase of 6.9 in a total score.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking distance measured by the Twelve Minute Walk Test (12MWT). 12minWT improvement was defined as a minimum increase of 90 meters.

The results for the secondary effectiveness endpoint for improvement in walking time with the Empower compared to the distance walked with the subject's passive prosthesis as measured by the 12 minute Walk Test (12MWT) at 3 months from four subjects were available for analysis.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking distance measured by the 10 Meter Walk Test (10MWT). 10MWT improvement was defined as a minimum increase of 0.1 m/s.

The results for the secondary effectiveness endpoint for improvement in walking distance with the Empower compared to the distance walked with the subject's passive prosthesis as measured by the 10MWT at 3 months from four subjects were available for analysis.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking time measured in the L-Test. L-Test improvement was defined as a minimum decrease of 4.5 seconds.

The results for the secondary effectiveness endpoint for improvement in walking distance with the Empower compared to the distance walked with the subject's passive prosthesis as measured by the L-Test at 3 months from four subjects were available for analysis.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in the walking time measured in theRamp Test. Ramp Test improvement was defined as a minimum decrease of 6 seconds to complete the test.

The results for the secondary effectiveness endpoint for improvement in walking distance with the Empower compared to the distance walked with the subject's passive prosthesis as measured by the Ramp Test at 3 months from four subjects were available for analysis.

The proportion of patients with a clinically meaningful change (improvement, no change, worsening) in abulatory activities measured by the Activities-specific Balance Confidence Scale. Improvement in the ABC was defined as a minimum detectable change of 13% increase in score.

The ABC Scale is a self-administered questionnaire that asks the patient to rate his or her confidence in performing various ambulatory activities on a scale from 0% (no confidence) to 100% (complete confidence) without losing balance or becoming unsteady. Scores for each of the 16 items will be collected and an average percentage calculated, with scores <67 indicating an increased risk of falling.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in ABC scale with the Empower at 3 months compared to the ABC scale with the subject's passive prosthesis as measured by the ABC scale.

The Falls Efficacy Scale is a validated 10-item self-report questionnaire designed to assess confidence in the ability to perform 10 activities of daily living without falling as an indicator of how one's fear of falling impacts physical performance. Each item is rated from 1 ("very confident") to 10 ("not confident at all"), and the per item ratings are added to generate a summary total score (10 to 100). Lower scores indicate more confidence and higher scores indicate lack of confidence and greater fear of falling. It has been validated for use in the elderly and persons with amputations. Scores ≥70 indicate an increased fear of falling. Improvement in the Falls Efficiacy Scale was defined as a minimum increase of 2 in the score.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in Falls Efficiacy scale with the Empower at 3 months compared to the Falls Efficiacy scale with the subject's passive prosthesis as measured by the Falls Efficiacy scale.

The AMP is an instrument designed to measure ambulatory potential of lower-limb amputees. Subjects begin the test seated in a hard chair with arms and are tested for a total of 21 items assessing abilities of increasing level of difficulty. Abilities assessed include sitting balance, transfer from chair to chair, standing balance, gait quality, negotiating obstacles, and the use of assistive devices. The total score range for the AMP is 0 to 47 points. A minimal detectable change of 4 points was the definition of improvement.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in AMP with the Empower at 3 months compared to the AMP with the subject's passive prosthesis as measured by the AMP Assessment.

The PLUS-M is a valid and reliable self-reported measure for the mobility of adults with lower limb amputations. PLUS-M asks about the patient's ability to perform simple and complex tasks. High PLUS-M scores correspond with greater mobility. Improvement in the Mobility PLUS-M (12 item Short Form) was defined by a minimum detectable change of an increase of 5 points in the total score.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in PLUS-M with the Empower at 3 months compared to the PLUS-M with the subject's passive prosthesis as measured by the PLUS-M measure.

The PSFS is a self-report, goal-attainment measure aimed at identifying functional status limitations that are most relevant to individual patients. The PSFS is a reliable, valid, and efficient measure for detecting clinical change in persons with low back pain and knee dysfunction. Subjects were asked to identify three to five activities that they are having difficulty or are unable to perform because of their injury/condition. For the specified activities, patients were asked to rate their ability to perform each activity at that time (0-10 numerical scale) with '0' being unable to perform the activity, and '10' being able to perform the activity at the same level as they could prior to the injury/condition. The total score was calculated as the sum of the activity scores divided by the number of activities. Changes of >2 in the total score compared to baseline were considered "Improved."

While 4 subjects completed the PSFS, the results from only one subject were available for analysis, since 3 subjects rated different goals at each time point. The secondary effectiveness endpoint was improvement in PSFS with the Empower at 3 months compared to the PSFS with the subject's passive prosthesis as measured by the PSFS.

The NPRS is a valid and reliable measure of pain that may be used across all musculoskeletal injuries/conditions and complements the PSFS. The patient was asked to rate the pain of their joints, foot, lower back, and if they are using an assistive device any additional affected limbs on average over the last 24 hours on a scale 1-10, with '1' being 'very mild' and '10' being the 'unimaginable unspeakable'. The scores on the NPRS instruments with the emPOWER Ankle were compared to the scores on the subject's passive prosthesis. An improvement was considered a positive change of 1 for at least one area without a corresponding decrease in another.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in NPRS with the Empower at 3 months compared to the NPRS with the subject's passive prosthesis as measured by the NPRS.

A Fitbit activity monitor was worn to record the number of steps the Subject took with the prosthesis. The patient returned to the site with the activity monitor and the steps counted were downloaded from the device. In addition, the Subjects were sent home with a prepaid envelope and instructed to mail back the activity monitor if the next visit was more than 3 weeks later, to ensure that the data was not lost. The step counts were downloaded from the device the day the activity monitor was returned to the Investigator. The Investigator recorded the date the patient was affixed with the activity monitor, the date they received the returned activity monitor, and the date they synced the monitor. An improvement was defined as an increase in the average daily step count of 750 steps.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in activity with the Empower at 3 months compared to the activity with the subject's passive prosthesis as measured by the steps counts from the Fitbit Activity Monitor.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Physical Function improvement was defined as a minimally clinically important difference (MCID) of an increase of 6.8 in a total score.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in PROMIS Physical Function with the Empower at 3 months compared to PROMIS Physical Function with the subject's passive prosthesis as measured by the PROMIS Physical Function.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Global Health Short Form improvement was defined as an increase in a total score of 3.5.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in PROMIS Global Health with the Empower at 3 months compared to PROMIS Global Health with the subject's passive prosthesis as measured by the PROMIS Global Health Short Form.

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Fatigue Short Form (7a) improvement was defined as a minimally clinically important difference (MCID) of an increase of 5 in a total score.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in PROMIS Fatigue with the Empower at 3 months compared to PROMIS Fatigue with the subject's passive prosthesis as measured by the PROMIS Fatigue Short Form (7a).

PROMIS item banks and their short forms are a reliable and precise measurements of patient reported outcome measures. The scores on the PROMIS instruments with the emPOWER Ankle 3 months after fitting will be compared to the scores on the subject's passive prosthesis. PROMIS Pain Intensity Short Form (3a) improvement was defined as a minimally clinically important difference (MCID) of an increase of 6.9 in a total score.

The results from four subjects were available for analysis for the secondary effectiveness endpoint for improvement in Pain Intensity with the Empower at 3 months compared to Pain Intensity with the subject's passive prosthesis as measured by the Pain Intensity Short Form (3a).

Self-Report Diary: Falls and daily activity. This was used to capture daily step counts from the Fitbit, daily activity and adverse events. It was a data collection tool, but was originally named as an Secondary Outcome.

Daily step counts were collected and reported for Secondary Outcome 12. Any reported falls were collected and reported as Adverse Events. Patient diaries were not collected, and no analysis was possible for other data recorded, such as daily activity.

Subject's own passive prosthesis: Devices varied.

The subject's own passive prosthesis was used as a baseline/control. No adverse events were collected prior to initial fitting with the emPOWER Ankle. After wearing the emPOWER Ankle for 3-4 months, subjects crossed over back to the passive prosthesis and wore it for 2 weeks. Subjects were crossed over back to the emPOWER for long-term follow up, up to 12 months after the initial fitting.

A subject reported having had an angioplasty procedure at the time of withdrawing consent. This event was not related to the device.