In addition to simply strength, the Hulk is generally recognized to have superior regenerative abilities to repair damage and actually prolong his life. This is more than enough to help repair any temporary joint damage which might occur during his activities.
This ability is present not only the comics version but was displayed in the 1970s/1980s T.V.show with Bill Bixby and Lou Ferigno. In it, Dr.Banner suffers damage to his spine causing paraplegia. Dr. Banner knows he can possibly regenerate if he "Hulks out". There is a scene in which he considers cutting himself on a sharp broken glass to bring out the Hulk. But, even though he knows it could help him Dr. Banner desists as he is afraid of risking hurting others. It was a nice moral touch showing Dr. Banner's humanity and concern for others. But, later in the show, as may be expected, Dr. Banner does experience anger, becomes the Hulk and regains the use of his legs as Dr. Banner as well.
More information on the Hulk abilities can be found at the Wiki Site:
EXCERPT FROM WIKI
His durability, regeneration, and endurance also increase in proportion to his temper. Hulk is resistant to injury or damage, though the degree to which varies between interpretations, but he has withstood the equivalent of solar temperatures, nuclear explosions, and planet-shattering impacts. Despite his remarkable resiliency, continuous barrages of high-caliber gunfire can hinder his movement to some degree. He has been shown to have both regenerative and adaptive healing abilities, including growing tissues to allow him to breathe underwater, surviving unprotected in space for extended periods, and when injured, healing from most wounds within seconds. As an effect, he has an extremely prolonged lifespan.