18 years old with Osteoarthritis pain and cortisone injection didn't work??

[Halfpint10]

At 15 years old playing basketball I tore my lateral meniscus and ended up having a bucket handle tear needing a partical menisectomy. After the surgery the pain did not really go away, I did rehab, I went to physical therapy but it just got worse and worse. After running a full track and basketball season I couldn't take the pain anymore and asked them to go in again, and they found a horizontal cleabage tear that had been there for nearly a year... So I'm now 18. 5 cortisone shots in, 2 knee surgeries down, and I've been diagnosed with mild/moderate osteoarthritis and only have 50% joint space left. I have been out of sports for a year now and have "let it rest" like my doctor said but have had 2 cortisone injections since last February. I am constantly in pain. My knee swells to the size of a cantaloupe and this last injection I got (Jan 16th) has had ZERO effect on me. I am still in constant pain, and I wake up with my knee locked almost every morning.. I'm afraid I have another tear or is this just the effects of the arthritis. Help please..??