What Does Grade 3 Chondromalacia Of Medial Femoral Condyle Mean?

I had arthroscopic on my right knee after a fall with direct impact on concrete. the dr thought is was a torn medial meniscus and it turns out it was not. the end result was grade 3 chondromalica of the medial femoral condyle and the facet of the patella. How could this be this serious when I have not had problems with my knees before.