Medial meniscus. Mild joint effusion.

My knee had swollen suddenly and I do not recall any immediate injury. As there is no injury doctor advised for MRI as normal x-ray would not be of any help.MRI report suggest following. Would like to know if Arthroscopy is required. Report Impression:  Flap tear along inferior aspect and inner margin of posterior horn of medial meniscus. Horizontal tear in posterior body and adjacent posterior horn of medial meniscus with small flap component of horizontal tear extending inferiorly to involve tibial articular surface in posterior horn. Grade 2 signal in rest of the body of meniscus. Mild cartilage thinning along inferior weight bearing su rface of medial femoral condyle. Focal areas of chondromalacia in midportion of the lateral tibial condyle and mid-portion of medial patellar facet. Rest of the cartilage along tibiofemoral and patellofemoral joint compartment appears normal. Focal area of bone marrow oedema in mid-portion of medial tibial condyle. Mild joint effusion.