Clinical results of femoropopliteal bypass using externally supported (EXS) Dacron grafts: with a comparison of above- and below-knee anastomosis. As of the end of September 1989, 52 EXS Dacron grafts had been implanted for femoropopliteal bypass operations. The distal ends of 27 grafts were anastomosed to above-knee popliteal arteries and those of 25 grafts to below-knee popliteal arteries. The cumulative patency rate of above-knee grafts was 71.3% at 54 months, and that of below-knee grafts was 78.8% at 48 months (n.s.). Kinking and stenosis of the arteriosclerotic proximal and/or mid popliteal artery when the knee was bent were angiographically remarkable. These changes may explain why some femoropopliteal grafts occlude with time and why the late results of above-knee grafts are not much better than those of below-knee grafts. 