Fibrous half-domed lumps of thickened skin and overgrown connective tissue, located just below a surfer's kneecaps or on the bony ridge of the feet, and sometimes on the joints of the toes; caused by the friction and pressure of knee-paddling a surfboard. Surfer's knots were a widely reported malady in the 1960s, during the later stages of the original longboard era. Pretty much painless and rarely infected, surfer's knots were in fact regarded as a status symbol, with a surfer's commitment and dedication to the sport measured in direct proportion to the height and circumference of his knots.
The American Medical Association did a study on surfer's knots in 1965, while Time magazine reported on a San Diego doctor who cut into a golf-ball-size knot, discovered "cords of pearly white material," and was paying $15 per surgically removed specimen. Time also noted that the knots were unrelated to "housemaid's knee," a form of bursitis, and that the growths would retract and disappear entirely within four to six months, once the surfer gave up knee-paddling. Surfers meanwhile discovered that foot knots, if big enough, would prevent an army recruit from fitting into standard-issue GI boots, and thus could be used to prevent a tour of duty in Vietnam. In the army induction scene from Warner Brothers' 1978 surf film Big Wednesday, a cane- wielding surfer takes a whack at his friend's knot in order to bring it up to the appropriately disqualifying size.
Surfer's knots vanished in the late '60s with the introduction of the prone-paddle-only shortboard, then reappeared about 15 years later—in far less numbers—as the longboard again became popular. Surfer's knots are also known as surfer's knobs and surf bumps.