Living tissues and organs are dynamic and change their mechanical properties and structure in response to stress alteration as a phenomenon of functional adaptation and optimal operation. This phenomenon is called 'Tissue Remodeling', and Wolff's law on bone remodeling is widely known. Several recent studies have shown that fibrous connective tissues such as tendons and ligaments also have the ability of remodeling. However, relatively little is known about the stress and motion effects on tissue homeostasis in biological soft tissues. This article primarily deals with changes of the biomechanical properties of knee joint tendons and ligaments through a wide variety of treatment modalities, including stress deprivation, recovery after stress deprivation, and stress enhancement. The experimental results indicate that tendons and ligaments have an ability to adapt in response to the change of stress if the extent of stress alteration is within allowable ranges.