Hip Muscle Strength Predicts Activity Limitation in Lower Limb Amputees

ORLANDO, Fla. — Hip muscle strength has the
greatest influence on walking in amputees, according to recent research.
Without strong hip extensor and abductor muscles, amputees face potentially
more difficulty in completing everyday tasks.

Led by Michele Alexandria Raya, PhD, PT, SCS, ATC,
assistant professor in the department of physical therapy at the University of
Miami’s Miller School of Medicine, and senior physical therapist at
Parkway Regional Medical Center, this research was selected for the Thranhardt
Lecture Series at the
2011 American Academy of Orthotists and Prosthetists Annual
Meeting and Scientific Symposium

Study findings

As part of her doctoral work, Raya worked to identify
the physical impairments that most affect a person’s ability to function.
The study focused on measuring impairments in
muscle strength and
balance and determining how deficits in these areas affect a
person’s ability to walk as measured by the 6-minute walk test.

  Hip Muscle Strength
  Image: ©
iStockphoto.com/David Bukach

“I decided to use amputees as subjects, as strength
deficits in their remaining musculature would be more pronounced and have a
greater effect on function,” she said.

Raya and her team recruited participants at an amputee
organization’s annual meeting, she told Academy Meeting attendees. In
total, they found 72 willing participants, with 61% being transtibial amputees
and 39% transfemoral. There were slightly more male subjects, and the time
since amputation ranged from 6 months to 56 years.

The researchers used the Amputee Mobility Predictor
(AMP) and a new, clinically friendly test specifically designed to measure hip
extensor and abductor strength, which together, both examined the skills needed
for successful prosthetic ambulation, Raya said.

She said she found that the strongest variable in the
study contributing to the distance walked in 6 minutes was the strength of the
hip extensor and abductor muscles, since these muscle groups are essential to
maintain pelvic control during ambulation, while also influencing the ability
to walk with symmetrical step length. Age also played a role.

While clinicians strongly suspected these findings,
evidence for this concept has eluded researchers, Robert S. Gailey, PhD, PT,
assistant professor in the department of physical therapy at the University of
Miami, said.

“I think the key from this study and many other
ongoing studies today is that we were looking at what are the contributions to
function in amputees, including how well an amputee walks,” he said.

Amputee implications

Raya said that the most significant implication of this
research is that it highlights the importance of maintaining sufficient
strength in the hip musculature. It is no surprise that patients who showed
greater strength subsequently performed better on all aspects of daily living
or recreational activities, Gailey said.

“We inherently believe that strength training,
especially at the hip, is a major contributor to how well somebody was able to
ambulate or function,” he said. “If you took all the variables that
determine how well somebody walks, and 30% has to do with hip strength, I think
that is a significant contribution.”

Gailey said this highlights what clinicians have
believed for years. First, it stresses the need for orthopedic surgeons to
ensure that muscles are in the proper positions and attached to bone so they
function to their maximum potential, or at their optimal length-tension ratio.

Next, it provides direction for physical therapists with
regard to preparing patients for their prostheses. The focus should be centered
on increasing the strength of the hip abductors, extensors and the other
muscles throughout the trunk and lower limb.

Finally, Gailey said, it emphasizes to prosthetists the
importance of creating a comfortable socket that will continue what the
surgeons started — positioning the muscles in such a way that they are

“For many years, what prosthetists have believed is
that a well-fitting ischial-containment socket will keep the femur in adduction
so we can use the hip adductors, and also in flexion so we can use the hip
extensors,” he said. “For the first time we realized just how
important that is to the patient and their overall ability to walk.”

It is basic knowledge, he said, that keeping core
muscles strong reduces the incidence of back pain related to postural faults.

For amputees, however, it goes beyond that, Gailey said.
Amputees must also maintain muscular strength inside the socket. A strong
residual limb can determine how well they will walk and reduce any gait

Moving forward

As a physical therapist who works with amputees, Gailey
suggests providing patients with two to three simple exercises, performed at
least three times a week, in order to maintain hip strength throughout the long
term. He pointed out that prior studies show that “about 60% of
transfemoral amputees are going to experience some type of back pain within 2
years after the loss of their limb.”

Maintaining hip strength and reducing gait deviations
and poor posture may alleviate some of those issues.

Speaking as a physical therapist with 20 years of
experience, Raya acknowledged that prosthetists are instrumental in helping
amputees to better use their hip extensor and abductor muscles through those
specific functional socket designs that put these muscle groups at the optimal
length tension.

“Working together, physical therapists and
prosthetists can help amputees better utilize their hip extensors and abductors
resulting in improved ambulation at the K3 level,” she said.

Gailey said that the lesson here is that prosthetic
outcomes are related to patients’ overall rehabilitative care, not just
their prostheses. The multidisciplinary approach to treating these patients
— including the prosthetist, physical therapist and orthopedic surgeon
— promotes the best long-term outcomes for patients.

“You can’t buy good gait. You have to work
toward achieving a proper gait,” he said. “That means that you have
to have the right socket, the right components and that you have to do the work
to get your body strong so that you’re able to utilize the components that
were prescribed for you.”

The best thing O&P practitioners can do for their
patients, Gailey said, is to consistently refer them to physical therapists for
gait evaluation, as well as therapy on how to use the new prosthetic
technology, and reinforcement about the need to maintain or develop their
strength throughout the whole body. Practitioners also should consider taking
steps to educate surgeons to the value of preserving and preparing the muscles
for the socket prior to performing surgery.

“An amputation is reconstructive surgery, shaping a
new body to perform the same tasks, only differently,” he said.

Raya told O&P Business News that the
overall reaction to the conclusions has been positive, but that further studies
are necessary in several areas, including socket design.

“Personally, I’ll be looking at developing
ways to better measure impairments that can be addressed to improve a
person’s functional abilities,” she said. — by Stephanie Z.


I could not agree more with the importance of hip
musculature strength in lower limb amputees. For the transfemoral amputee, this
is the primary factor in determining a person’s ability to ambulate with
or without an assistive device. In many cases weak hip extensors are usually
paired with a hip flexion contract. Without addressing this imbalance through
stretching and strengthening, efficient prosthetic ambulation is not possible.
Due to the absence of the functional range of motion at the hip, pelvic tilt
and rotation are negatively affected. The result is the amputee using excessive
trunk compensatory motion, usually excessive lumbar lordosis and hip hiking to
bring the prosthesis through the swing phase of gait, which leads to a
reduction in the efficiency of prosthetic gait, resulting in decreased
prosthetic use, and with time, possible low back problems.

As a prosthetist, I may not be able to influence the
surgical technique nor the initial physical therapy that my transfemoral
amputees receive. What I can do is place these amputees in a well-fitting and
comfortable socket system. Most importantly, align their prosthesis to meet
their individual hip range of motion and strength needs. That will also
encourage proper hip biomechanics.

— Shandon Hime, CPO, FAAOP
Founder, owner
and head of clinical operations, Anatomical Designs


The building blocks of prosthetic success are being
revisited with this study. A team approach in prosthetic care is a standard in
the field. The authors illustrate the value of a team approach, starting with
surgical technique, prosthetic socket design, alignment and onto physical
therapy and rehabilitation. This study narrows the focus of the team approach
to the concept of muscle function for amputees.

It is crucial to understand that pelvic stability is a
lynchpin to prosthetic success. This research on how hip muscle strength
predicts activity limitations in lower limb amputees pulls the fundamental
elements of patient care together and highlights the extreme importance of
planning for a patient’s success, starting in the operating room.

Often the basics get lost in the daily shuffle. This
important new research reemphasizes the elemental building blocks needed for
the success of our patients. It is important to not only understand that hip
muscle strength is the keystone to prosthetic function, but also that
collaboration between surgeon, prosthetist and physical therapist for muscle
planning and strengthening is just as critical. The lessons of this study
remind us to refocus our efforts on the importance of surgical technique,
prosthetic alignment, gait training and most importantly muscle conditioning.

After all, a nicely shaped limb in a well fitted socket
is of little value unless the patient has the stability and physical ability to
attain maximum function.

— Sarah Thomas, BS, CPO
Bio-Medic Appliances Inc.


After review, I believe the findings of this research are significant to
practitioners in improving the overall outcome of a patient who is wearing a
prosthesis. I have focused on the importance of hip extensors for prosthetic
knee extension more than pelvic control. From attending clinics presented by
Robert S. Gailey, PhD, PT, I have learned that what is happening at the pelvis
directly affects gait. This isn’t a new concept, but one that is often
overlooked. Practitioners often focus on making adjustments to the prosthesis
to improve gait as opposed to evaluating muscle strength as the problem. The
therapists I work with are always looking for suggestions on how to prepare a
person with an amputation for prosthetic management. This is another tool to be
added to the chest.

Dan Smoker, LPO
Alabama Artificial Limb
& Orthopedic Service Inc.

Leave a Reply

Your email address will not be published.