Hi thanks for your query and welcome to lybrate. I am Dr. Akshay from fortis hospital, new delhi. Actually decision in a knee depends upon a thorough clinical examination for all structures and then correlating findings with mri of affected knee.
My take on this is: I think you should go for a diagnostic arthroscopy and then proceed.
This will help in 2 ways, first we can see all structures inside ot with our own eyes and see for complete
tears and laxity.
Complete acl tear ar your age will require a reconstruction arthroscopically, lateral meniscus can be balanced and managed. Do not hesitate to contact me if you need any further assistance.