It's the ankle and leg. If you watch the scene, the alien drops like Ethan Hunt, and its feet catch on the bar. The body moves lower so the legs get more vertical. You can see in the scene the both of the legs are there, and they wobble where the end of Bodejo's heels are.
It's like if you were doing incline push-ups and for some reason decided to lower yourself into position from above. Your heels would be above your head, which is what we see here.