A Rush University Medical Center study has found that flip-flops and
sneakers with flexible soles are easier on the knee joints than clogs or
specially designed walking shoes. The amount of loading force on the knee
joints is a key factor in the development and progression of
Najia Shakoor, MD, rheumatologist at Rush University and lead author of
the study, analyzed the gait of 31 osteoarthritis patients — 10 men and 21
women — using an optoelectronic camera system and multi-component force
plate at the Rush Motion Analyses Lab. Each patient’s gait was evaluated
while barefoot and while wearing four different types of shoes — clogs,
stability shoes, flat walking shoes and flip-flops. The peak knee loads of the
osteoarthritis patients were compared under the different foot conditions.
The study’s results indicated that walking barefoot, with
flip-flops or with lightweight flexible-soled shoes lowered the amount of force
on a patient’s knee joints. These characteristics of the shoe accurately
mimic the biomechanics of the foot, thus lowering their knee load. The 11% to
15% reduction in load by the different footwear was comparable to the amount of
load reduction by orthotic braces or shoe inserts.
“Everyone needs a pair of shoes, so finding the right shoe may be a
more practical way to intervene rather than going straight to an orthotic or
brace,” Shakoor suggested to O&P Business News.
Her study indicated that shoes thought to offer support and comfort to
the foot, such as stability shoes or clogs, actually produced greater knee
loads. According to the study, the loads of the knee joints for patients
wearing clogs or stability shoes were up to 15% greater than with the
lightweight walking shoes, flip-flops or barefoot walking.
“Shoes have traditionally been made for the foot but without much
regard for the rest of the body,” Shakoor said. “Shoes are generally
designed with the biomechanics of the foot and ankle in mind. But shoe
manufacturers have not extensively looked beyond the biomechanics of the
Shakoor’s field is beginning to embrace the trend that comfort for
one’s feet does not necessarily mean comfort for the rest of your joints.
“Theoretically, if you put a high force on your knee joints, you
may be someone that is potentially putting themselves at greater risk for
osteoarthritis,” Shakoor said.
Shakoor is currently enrolling patients for a study that determines how
osteoarthritis patients tolerate wearing the shoes and how they affect the
patient’s feet and the rest of their body.
“This was a short study in a lab setting,” Shakoor said.
“So we have not really looked at the long-term health and pain as the
patients wear their shoes for extended periods of time.” — by
I am concerned about someone telling a friend with arthritis, ‘Go
ahead and wear flip-flops, you won’t have any problems.’ It is
dangerous to think that way.
Yes, the direct force on the knee is lowered while walking in a barefoot
manner or wearing a flip-flop, but torque on the knee is not discussed and it
is the most important aspect. That is how you wear out the knee.
Many of these studies are narrowly focused on a basic piece of
information rather than going back and taking a more in depth look. Now, the
authors of the study do say they will go back and look at the research in the
future and I give them credit for that.
I just worry that the only message taken from this study is that people
can wear flip-flops all the time. But people must be aware of what flip-flops
can do to their hip if they are continually worn. Your alignment is
considerably worse after a couple weeks of wearing flip-flops. The rotation of
the hip can be thrown off eight to 15 degrees. Your hip could potentially be
worn out at a much younger age.
Torque adds a tremendous amount of pressure and rotation to the knees
and hips and those are things that we have to protect against. It is not just
one-dimensional. Biomechanics is supposed to mean everything.
‘Biomechanics’ is a word that encompasses how you move in all areas.
It is not singularly focused on one aspect.
—Art Smuckler, CPed