Sounds like your father has had a an acute exacerbation of Ostearthritis or Wear & Tear Arthritis. Unlike to have Rheumatoid Arthritis
starting off at this age. Show him to a Rheumatologist
or an Orthopaedician for effectively managing this condition. Usually a course of anti-inflammatories, hand splintage, ice & gentle hand physiotheerapy should make him comfortable and prevent recurrences.