I know it is not considered one of the compensatable diseases caused by agent orange, but has anyone ever been given a disability rating for ostearthritis?

My husband has a service connected back injury w/ arthritis that is rated at 10%. He just had a total knee replacement a week ago. He needs to have his other knee replaced, & his shoulders. He has no cartlidge left in his thumbs and more arthritis in his feet.

Is there any chance a doctor would ever connect the rest of his arthritis in his body with the original service connected back injury which resulted in the injured area becoming arthritic?

He had a spinal MRI done recently which showed DDD, bulging discs, arthritis and spurs. Is it worth asking for an increase in his rating?

Any thoughts are appreciated. Thank you!