Abstract: Based on the non-uniform settlement theory of professor Yingze Zhang,the tibia,as a load-bearing bone,takes place apparent settlement due to osteoporosis in the human aging process,which does not occur in the fibula.Therefore,it leads to medial compartment of knee and ankle arthritis simultaneously.For the medial compartment of ankle arthritis,the fibula can be cut 1 - 2 cm at 6 cm above the lateral malleolus.And it will restore ankle joint space, effectively relieve pain.