Entitlement to service connection for a left knee disorder is remanded.

Board reasoning

The Board finds pre-decisional duty to assist errors require remand to obtain a medical opinion on whether the Veteran's current knee disorders are related to service, including the documented October 1977 knee injury and the Veteran's lay statements about ongoing symptoms. The examiner must provide a complete rationale, consider service records, and address gaps in time between service and onset, as well as lay evidence and articles submitted by the Veteran. The intertwined claims for back conditions are remanded for consideration with knee issues to promote judicial economy.