Mechanical stimulation is critical for bone architecture and bone mass. The aim of this study was to examine the effects of mechanical loads applied to the knee. The specific question was whether loads applied to the tibial epiphysis would enhance bone formation in the tibial diaphysis. Using C57/BL/6 mice, loads of 0.5 N were applied for 3 min per day for 3 days at 5, 10, or 15 Hz. Bone samples were harvested 13 days after the last loading. The strains were measured 13 ± 2 µstrains at 5 Hz in the diaphysis. The histomorphometric data in the diaphysis clearly showed enhanced bone formation. First, compared to nonloaded control the crosssectional cortical area was increased by 11% at 5 Hz and 8% at 10 Hz (both p < 0.05). Second, the cortical thickness was elevated by 12% at 5 Hz (p < 0.01) and 8% at 10 Hz (p < 0.05). Third, mineralizing surface (MS/BS), mineral apposition rate (MAR), and bone formation rate (BFR/BS) were increased at 5 Hz (p < 0.01 for MS/BS; p < 0.001 for MAR and BFR/BS) and at 10 Hz (p < 0.05 for MS/BS; p < 0.01 for MAR and BFR/BS). Bone formation was enhanced more extensively in the medial side than the lateral or the posterior side. The results reveal that knee loading is an effective means to enhance bone formation in the tibial diaphysis in a loadingfrequency dependent manner without inducing significant in situ strain at the site of bone formation.