It's a meniscus REMOVAL. A torn meniscus, when it's still stuck in the knee, will cause a lot of pain and problems (locking, catching, etc.).
When you remove the piece, all those problems go away. If he had a meniscus REPAIR surgery instead, he would still be stuck in rehab for many more months.
And then, some years down the road, you'll get an early onset of arthritis due to not having the meniscus (shock-absorber) anymore.
Being a rich footballer, he can probably opt for a meniscus transplant after retiring (not guaranteed, but sometimes works).