“on its last legs”别理解成“在后腿上”,真实含义是快用坏了，快用到头了，奄奄一息，垂死挣扎，临近死亡，将遭淘汰。

【例句】
And if you ask me, the company is on its last legs.
要我说，这家公司在做最后的垂死挣扎。

The blender stopped working again today—it must be on its last legs.
搅拌机今天又不工作了，一定是快用到头了。