Knee osteoarthritis (OA) is a serious degenerative disease affecting over 240 million people around the world. The most disabling symptoms are joint pain, joint stiffness, and reduction in joint functionality. Medial compartment knee OA is the most common case of unicompartmental knee OA, and pain and progression have been associated with tibiofemoral alignment in early to moderate knee OA patients, mainly due to its association with knee loading as measured by knee adduction moment (KAM) and tibiofemoral contact forces (KCF). Valgization knee braces have been developed to correct the malalignment at the tibiofemoral joint, but they have no direct effect on knee OA progression and joint contact forces. This has been explained by increased muscular activity, and neural adaptation to external knee brace loading, since muscle forces are the main contributors to knee contact forces. Muscular activity reduction has been achieved on healthy subjects through the implementation of exoskeletons and active orthoses. Integrating similar approaches into current knee bracing methods may reduce muscle activity around the knee joint, therefore achieving a reduction in KCF, and potentially reducing knee OA symptoms and slowing down disease progression. After identifying the specific external knee assistance requirements for level walking, stair ascent, stair descent, stand-to-sit-to-stand, a clutch-based knee brace was built to meet the corresponding behavior for each of these daily life activities. The device was tested to quantify its biomechanical effects on one healthy subject during these activities, and changes in knee muscle co-contraction index, knee joint internal contact forces, and kinematics were reported. Stand-to-Sit-to-Stand (STS) showed the highest peak contact force reduction due to external assistance, moreover, the reduction in knee contact forces for the STS task was found to be directly proportional to the level of external assistance applied. Our research reveals the capacity of semi-active knee bracing as a tool for tibiofemoral contact forces reduction, and its potential to be extrapolated as a non-invasive treatment to slow down the disease progression in knee osteoarthritis patients.