Purpose: Osteoarthritis of the knee (OAK) is degenerative disease and nearly 9.3 million at age ≥26 in the USA are affected by this disease and a leading cause of personal suffering and economic burdens to society. The radiographic pathology of advanced OAK in antero-posterior view is characterized by osteophyte at tibial spine (TS) and joint space narrowing (JSN) and osteophyte at joint margin (JM). Kellgren-Lawrence (K&L) developed the universal system to diagnose osteoarthritis of shoulders, wrists, hips, knees, ankles, etc., in 1957, and this system has been widely used to diagnose OAK 1961. The criteria of K&L system, however, appears to be inadequate: the site of osteophyte at TS and JM is vague in grades 1 and 2; and only JSN is used in grades 3 and 4 without including osteophyte at TS and JM. It has caused a difficulty in diagnosis of all OAK especially early OAK and some urge for a need of new system. Methods: Kinematically, the knee employs medial TS as an axis, while medial and lateral compartments carry the load. It allows for dividing the OAK pathologies into two sites in kinematic aspect: the pathology at TS; and the pathology at condyles. It helps develop two radiographic OAK-markers: axial OAK marker (AOM) to measure osteophyte at TS; and condylar OAK marker (COM) to measure JSN and osteophyte at JM. 1) For the criteria of AOM, the distance between the apex of normal TS and roof of intercondylar notch is divided into four grades: normal (0+); mild (1+); moderate (2+) and severe (3+). 2) The COM is divided into COM A and COM B: a) COM A to measure JSN and b) COM B to measure osteophyte at JM. The criteria of COM A and COM B are following: a) COM A: The joint space of non-narrow opposite compartment is divided into four grades: normal (0+); mild (1+); moderate (2+) and severe (3+). b) COM B: normal (0+); mild (1+); moderate (2+) and severe (3+). Then, the value of COM A and COM B are combined to assess the overall COM value. Then, the severity of OAK can be described by AOM/COM in two numbers: mild OAK (1+/1+), moderate (2+/2+), severe OAK (3+/2+), etc. With these two markers, both knee radiographs of 1,728 patients with knee pain are magnified and analyzed. Results: It shows that in 611 knees, subtle osteophyte at TS only (1+/0+) is in 562 (92%) and squaring, beaky JM only without JSN (0+/1+), in 49 (8%). The knee with (1+/0+) or (0+/1+) is defined as early-stage mild OAK unveiling new fact that OAK starts to develop at TS or JM. Then, the knee with mild osteophyte at TS and beaky JM and mild JSN (1+/1+) is defined late-stage mild OAK. It helps develop two radiographic classification systems in kinematic aspect to diagnose all OAK in mild, moderate or severe severity, and early-, intermediate- or late-stage: 1) a system to diagnose OAK starting at TS; and 2) a system to diagnose OAK starting at JM. Analysis of OAK radiographs based on new systems shows that all mild OAK (1+/0+, 0+/1+, and 1+/1+), which is 47.4% of all OAK, has been missed by K&L system. Then, 9.3 million OAK at age ≥26 diagnosed by K&L system was only moderate and severe OAK, and missed-mild OAK in the USA was 8.4 million and worldwide, 187 million, for the USA population is about 4.5% of the world. This 187 million mild OAK missed would have deteriorated to moderate and severe OAK, having caused current personal suffering. To diagnose missed-mild OAK, MRI has often been used having caused heavy economic burdens to society. Conclusions: Subtle osteophyte at TS and squaring of JM are the earliest radiographic sign of OAK. Two new radiographic classification systems in kinematic aspect are offered to diagnose OAK in severity and stage, unveiling missed-mild OAK before deteriorating to moderate-severe OAK without MRI, forestalling personal suffering and economic burdens to society in the future.