Van Zyl, running her second marathon in three weeks after returning from a lengthy injury layoff, was among the early leaders in the lucrative race, but ultimately dropped out.
Ethiopian Meseret Biru went on to win the women’s race in 2:31:00.
“My knee acted up just after 26km with all the different surfaces and then just after 32km we had to run up and down a flight of stairs,” Van Zyl said.
“After that, I couldn’t take the pain any more and my knee just collapsed after 33km. I didn’t want to stop but my knee forced me to.”