I had surgery for a medial and lateral meniscus tear 4 months ago. i still have pain when i completely straighten my leg. scar tissue?

Meniscal tear postop: It could very well be scar tissue. The meniscus (or menisci-plural) may have continued to tear also. My guess is that you may have underlying arthritis, which often gets exacerbated with a knee injury. The location of your pain is also very important. I would recommend having your surgeon that did the knee scope check you out again if the pain is significant.