The Veteran's lumbar DDD is rated at 20 percent, and the initial 20 percent rating for left lower extremity neuropathy is granted.

The Board denied service connection for various conditions, including left and right eye dry eyes, cataracts of the left and right eyes, neuropathy of the left lower extremity, radiculopathy of the right lower extremity, left renal arteriovenous malformation, aneurysm, pseudofolliculitis barbae (PFB), degenerative joint disease (DJD) of the lumbar spine, recurrent subluxation of the left knee prior to May 13, 2020, left total knee replacement, disability rating in excess of 60 percent from September 1, 2021, forward for left total knee replacement, DJD of the right knee, right knee instability, burns of the bilateral ankles, linear scar of the left knee, post-surgical tender scars of the left knee, and a total disability rating due to unemployability (TDIU) based upon service-connected disabilities prior to June 14, 2019.

The Board denied the veteran's claims for increased ratings for lumbar degenerative disc disease, left and right knee strain with tendinitis, and gastroesophageal reflux disease. The TDIU claim was dismissed.

The Board granted service connection for hyperthyroidism as secondary to in-service exposure to herbicide agents, and for neuropathy of the right and left lower extremities and right eye exophthalmos and diplopia as secondary to service-connected hypothyroidism.

The Board remands the claims for service connection for neuropathy of all four extremities due to a need for additional development, including verification of claimed nerve agent exposure and obtaining an updated medical opinion.