膝關節正側位影像中，主要可以診斷膝關節的骨折或脫位，剝脫性骨軟骨炎或髁狀突上方滑液囊積水等。但實際臨床上，大部份放射師照膝部側位影像時，要照完全正側位並不是那麼容易。所以本篇研究將膝部側位攝影擺位技術分為： X 光球管垂直照射、 X 光球管向頭打3~7 度、利用支撐物將腳踝墊高、 X 光球管向頭打3~7度與將腳踝墊高、跨檯投照等五種。由結果發現將患側膝部彎曲15~30 度，X 光球管還要向頭打3~7 度，並在患側腳踝墊支撐物，讓膝部貼近片匣，如此便可得到最佳的膝部正側位影像。

A true lateral knee image can diagnose fracture, dislocation, osteochondritis dissecans, supracondylar bursa of the knee joint. However, the actual clinical practice, the majority of radiologists projected lateral knee image according to the true lateral view is not entirely easy. Therefore, this study will be lateral knee positions divide into X-ray tube vertical exposure,X-ray tube turn 3 to 7 degrees cephalad, a support use of ankle to elevate, X-ray tube turn 3 to 7 degrees cephalad and elevate the ankle, cross-table. The results were found to flexing the affected knee 15 to 30 degrees, X-ray tube would turn 3 to 7 degrees cephalad, and the affected ankle pad a support, so that the knee closer to the cassette, and so will be able to get the best true lateral knees images.