Degenerative changes usually means signs of wear and tear that are usually normal in an adult, sportsmen may see these earlier due to excessive use on the joints.
Sub articular cysts are also seen in arthritis and post-trauma bone injuries.
The actual context of the report and the clinical reason for the report need to be considered in light of the findings.
Do you have the report summary or 'impression'?
Summary of Impression
Medial meniscus tear
Lateral collateral ligamament tear
De generative changes and subarticular cyst in tibia
I would not worry about the degenerative changes and sub articular cyst at the moment. The cyst is likely to be an incidental finding and will have no influence.
The medical meniscus tear may cause locking of the joint and may need to be trimmed and the lateral collateral ligament tear will contribute to joint instability. The decision to treat the ligament tear will depend on stability of joint. Sometimes if the joint is stable then no intervention is done aside from short term knee support.
So you need to have a chat with your surgeon regarding your options.