Translation:After all, neither his spine nor his knee is ill.
People are ill, whereas spines and knees are injured.
Yes, the English translation given here is understandable but incorrect.
The chances of getting this one right the first time approach zero.
Second time too! "Végül" and "gerince" and "térde" all seem completely new (I know they're not, but they seem it).
I used "her" rather "his" and got marked wrong... Tsk tsk... naughty Duo!
Why is it "his spine" and not "the spine"?