It is the lactose induced hypertension that concerns us here. Tension restricts blood flow and inhibits the body's ability to repair itself. This, plus the fact that tension puts added pressure on one's joints is how I see arthritis developing from lactose induced tension. The connection between milk and arthritis has also been noted by other researchers. It is very, difficult to prove the relationships I have just described.
Human life is very complex and often several things can cause the same symptoms.
For a number of years, a friend of mine was admitted to the hospital a couple of times a year, with chronic symptoms the doctors were treating as pneumonia using oxygen tents and antibiotics. She was finally taken to an allergist. The cause of the symptoms was an allergy to chocolate. He is right. Taking aspirin only relieved mother's symptoms.