The meniscus is crescentic, with two horns (like a new moon) - and the posterior horn is the one at the back.

posterior horn of meniscus
The horn at the front is called the anterior horn.

 

Issues of the posterior horn

Because the rounded ends of the femur obscure much of the posterior horn, it is difficult to see during routine arthroscopy. By putting the knee into a 'figure-4' position, the back of the joint can be opened up and the posterior horn can be examined with a probe.

-

Meniscus from top

Another view of the 'knee cartilages'.

Knee meniscus

Overview of the anatomy of the 'knee cartilages'.

-