What if you have a tear in acl and never get surgical treatment?

Unsure: You might get some tissue hypertrophy and sclerosis which could add to the tensile strength of the previously weakened ligament. You also may completely tear it by simply stepping off of a curb if it remains weakened. See your doctor.

Cartilage tears: A knee with a non-functioning acl is often unstable. Meaning, the acl can no longer prevent the tibia from sliding forward or rotating abnormally. Thus, the cartilage structures, primarily the medial and lateral menisci, are at higher risk for tearing. This can often lead to increased pain, swelling and catching in the joint. A younger & more active patient often has a better outcome with surgery.