Can a orthovisc injection weaken the medial meniscus? also unable to straighten the knee ?

Should not weaken : Orthovisc should not injure any part of the knee. The needle could cause damage, but that is unlikely in skilled hands, and less likely still if guidance were used. I suspect you received the orthovisc because you had significant wear and tear in the knee, and that might explain why you can’t straighten the knee. Hopefully when the med starts to work, you will improve. If not, call,the doc.