Quantitative microfocal radiographic assessment of osteoarthritis of the knee from weight bearing tunnel and semiflexed standing views.

OBJECTIVE Joint space width (JSW) in osteoarthritis (OA) knee radiography is reported to be optimally assessed from semiflexed standing and tunnel views although no detailed assessment of tunnel view radiography of OA knees has been done. The primary objective of our study was to determine the incidence of joint space narrowing (JSN) in semiflexed standing vs weight bearing tunnel views. The data were also analyzed to examined the degree and relationship of JSN and bony features of OA in the 2 views. METHODS Ninety OA knees had macroradiographs at 5 times magnification taken in weight bearing standing semiflexed and weight bearing tunnel views. JSW and OA related bony features were measured and compared with reference values obtained from the knees of 14 healthy volunteers without arthritis. RESULTS Comparison of JSW between the 2 radiographic views identified 3 locations of cartilage loss: JSN recorded in the tunnel only (22%), that in standing view only (8%), and that in both the views (30%). Subchondral sclerosis and osteophytes were significantly larger in 40% of OA knees despite a normal JSW. The tunnel view also enabled better visualization and measurement of osteophytes. CONCLUSION Standing semiflexed view radiography alone failed to detect JSN in 22% of OA knees. Combined standing and tunnel radiographic views detected JSN more frequently than either view alone. Bony changes were radiographically evident without the presence of JSN indicative of cartilage thinning in as many as 40% of the patients with OA studied.