Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.

Standard Rehabilitation Protocol: All participants will receive the current standard of care at the 2 military sites (Walter Reed National Military Medical Center (WRNMMC) and Malcolm Grow Medical Clinics and Surgery Center (MGMCSC)) of the physical therapy rehabilitation protocol for knee injuries. This program includes treatment with a physical therapist at WRNMMC and MGMCSC physical therapy clinic.

NMES (EMPI 300PV stimulator) plus SRP: NMES training consisted of four 30-minute stimulation sessions per week for 12 weeks; each 30-minute session entails 15 minutes/leg with 15 contractions per leg.

Weeks 1-3: 15-20% of maximal voluntary contraction (MVC); Weeks 3-6: 20-30% of MVC; Weeks 6-9: 30-40% of MVC; Weeks 9-12: 40-50% of MVC; Weeks 12-18: sustain 50% of MVC. Incremental increases made at the 3, 6, 9, and 12-week clinic visits.

Home-Based Pedometer-Driven Walking Program plus SRP: Participants were given a pedometer to monitor daily steps and a weighted exercise vest at Week 7 to begin the strengthening component. A series of 10-minute lessons focused on increasing physical activity through lifestyle education and the use of a pedometer as a motivational tool.

Participants maintain a daily training log. Pedometer readings used for setting activity goals. Initial step goals: 10% above the average 3-day pedometer step count at baseline. A 10% increase every other week, then a gradual increase when 30% above the baseline step count has been achieved. At week 7, participants will be given a vest to begin the strengthening component. The beginning weight load for the vest is calculated using 2% of baseline body weight and increased by the same amount every week until the end of the 12 weeks.

NMES, Home-Based Pedometer-Driven Walking Program plus SRP: This group will follow the protocol for both the NMES training and Strength Walking.