Gait modifications, such as lateral trunk lean (LTL), medial knee thrust (MKT) and toe-in gait (TIG), are frequently investigated interventions used to slow the progression of knee osteoarthritis. The Lerner knee model was developed to estimate the tibiofemoral joint reaction forces (JRF) in the medial and lateral compartments during gait. These models may be useful for estimating the effects on the JRF in the knee as a result of gait modifications. We hypothesized that all gait modifications would decrease the JRF compared to normal gait. Twenty healthy individuals volunteered for this study (26.7 ± 4.7 years, 1.75 ± 0.1 m, 73.4 ± 12.4 kg). Ten trials were collected for a normal gait as well as for the three gait modifications: LTL, MKT, and TIG. The data was used to estimate the JRF in the first and second peaks for the medial and lateral compartments of the knee via OpenSim using the Lerner knee model. No significant difference from baseline was found for the first peak in the medial compartment. Statistically significant effects from baseline were found for the medial second peak as well as the first and second peaks in the lateral compartment. While there was a decrease in JRF in the medial compartment during the loading phase of gait for both TIG and LTL the differences were not statistically significant. MKT showed an increasing JRF in the medial compartment but was also not significant.