Are Flip-Flops Really That Bad For Your Feet?

I was sitting at a nice table in the Pub Med, on the east edge of Academiaville, chatting with a professor buddy of mine named Google Scholar. He likes to be just called “Googie.” Seems like that rogue is in every little academic nook and cranny, but I love him.

The cool thing is that we were “flip-flopping” back and forth about different issues. One of us would take the position that was the opposite of our true opinion just to spur debate and allow for mental expansion. Sometimes, it is very fun trying to argue for what you really disbelieve. Then we would do that most daring thing of all: look at the evidence. Opinions be damned. We are professors and that means we have to be purveyors of truth and other erudite stuff like that. Don’t confuse my misguided dogmatic beliefs with any of that evidence-based stuff, or you know what? I might just have to change my mental picture.

The Pub Med is an interesting venue. At each table, there is a touch screen on which you can literally pull up the answer or at least the research on virtually anything dealing with medicine. Want to know how many prolapsed uteri that are fixed in the United States each year and what the procedure of choice is? Touch that damn search button after inputting a few simple keywords and the gynecological world is your oyster. Hell, in the old days, you would have had to blown out three disks carrying those heavy dusty texts from the Dewey Decimal System shelves before finding out what uteri really meant. Now, one click and I can read Bush’s seminal 1972 article on a prolapsed uterus in a pigmy hippopotamus.¹

Did you even know that there were pigmy hippopotami? I didn’t. Really, this must be like that “jumbo shrimp” deal or the “biggest little town” type of thing.

So Googie and I are busy drinking some fermented wheat juice (gluten be damned), and bantering back and forth, playing a game we like to call “mind bender.” All of a sudden, he looks down at my flip-flop-shod feet, and gasps audibly so loud that the entire establishment freezes their index fingers atop their search buttons, and screeches: “My God, man, you are a foot surgeon and you are wearing flip-flops? What the hell are you thinking? Don’t you know those things cause all types of problems and are the root of all foot evil?!”

“Really,” I replied with a tone of feigned arrogance. “I wear these all the time and I seem to do just fine.”

Googie was now visibly upset. “I just read in the newspapers three different articles from ‘foot experts’ telling everyone how bad those things are for your feet.”

I snarled, “Bad,” as I extended my digitus secundus manus toward the omnipotent touch screen. I quickly typed several keywords: “Flip-flops, effect on gait, and injury.” The screen flickered with the spinning little colored wheel for a few seconds and BOOM, there it was. The entire body of peer-reviewed journal articles on flip-flops and their heinous effect on pedal happiness. So what did the screen show me?

Not much. There were three studies and one was mine.^2-4 Yet the pontificators are out there on their soapboxes yelling at the unknowing public that flip-flops are bad for everyone and everything. Really? According to Shakoor and colleagues, flip-flops actually help patients with osteoarthritis of the knee.³ The authors used some high-tech gadgetry like optoelectronic cameras and multicomponent force plates and compared peak knee load pressures in four groups (those wearing clogs, people wearing stability shoes, study participants wearing flat walking shoes, and people who wore flip-flops) to folks who walked barefoot.

I could tell Googie was getting agitated as he kept pushing up his Buddy Holly glasses and scratching what he called a goatee. My dishwashing brush had more substance but that is a whole different discussion. “So go on,” he implored.

“Well, according to these boys (some may be female but this is storytellin’, not gender sensitivity class), people wearing clogs and stability shoes had the highest peak pressures, and there was no statistical differences when walking with flip-flops or walking shoes in comparison to barefoot walking.”³ Now that is different than our own findings in a 2008 study that found higher in-shoe peak pressures for flip-flops in comparison to sneakers. However, as with the other group, there was a positive finding for the much maligned flip-flop: lower peak pressure than barefoot walking.²

Now we know that you have to grip those damn things with your toes to hold them on, and that has something to do with a change in gait. But is it as severe as the pontificators proclaim?

Not so fast, my partially foot shod friend. Chard and coworkers studied the effects of “thongs” (that’s what they called them—not my word, but I must refrain from any further comment on their nomenclature, and get back on track) on the feet of 13 healthy children.⁴ They used high-tech gadgetry, including kinematic recording, as well. What they found was also quite interesting. During walking, subjects wearing flip-flops had increased ankle joint dorsiflexion and decreased dorsiflexion at the first metatarsophalangeal joint. Could this perhaps be a benefit for the patient with hallux limitus?

“So, Googie,” I said smugly. “From an evidence-based medicine standpoint, we really don’t know squat about flip-flops and what they really do from a gait and injury standpoint.”

He learned back with an earnest look, sighed, and said, “You should probably have some laser on that second nail. It looks fungal.”

References

1. Bush M, Lemken R, Moore JA. Prolapsed uterus in a pigmy hippopotamus. J Am Vet Med Assoc. 1972; 161(6):651.

2. Carl TJ, Barrett SL. Computerized analysis of plantar pressure variation in flip-flops, athletic shoes, and bare feet. J Am Podiatr Med Assoc. 2008; 98(5):374-378.

3. Shakoor N, Sengupta M, Foucher KC, Wimmer MA, Fogg LF, Block JA. Effects of common footwear on joint loading in osteoarthritis of the knee. Arthritis Care Res. 2010; 62(7):917-923.

4. Chard A, Greene A, Hunt A, Vanwanseele B, Smith R. Effect of thong style flip-flops on children's barefoot walking and jogging kinematics. J Foot Ankle Res. 2013; 6(1):8.