Do Football Players Have a Greater Risk of Developing a Hip
Impingement?
Madeline Kay Johnson and Robert Stow, PhD
Department of Kinesiology, University of Wisconsin-Eau Claire, Eau Claire, WI
Acknowledgements
We would like to thank Dr. Matt Evans and the Blugold Fellowship program for making
this project possible. We would also like to thank Drs. Nathaniel Stewart and Karl Stein for their
contributions towards this project as well as the senior athletic training students and staff for
their assistance with data collection. We would also like to thank Dr. Jeff Goodman for his
assistance with the statistical analysis, and Robert Stow for his work that made this project
possible.
Abstract
The intent of this study was to investigate the hip characteristics of collegiate level
football players in relation to the characteristics of patients suffering from femoroacetabular
impingement. In addition, examination of football playing position was analyzed to see if
differences arose. Femoroacetabular impingement (FAI) is caused when the neck of the femur,
due to limited internal rotation, biomechanically contacts the pelvis in an atypical manner. Data
was collected from participants from the University of Wisconsin- Eau Claire football program
including measurements of hip range of motion and a hip impingement test. Results showed that
5.9% of football players tested positive for hip impingement, compared to 2.3% of the other
sports. Football also showed a significantly (p<0.05) higher rate for clinical positives in
decreased hip internal rotation and flexion. In regards to football playing positions, offensive and
defensive line positions were significantly more likely to have decreased hip flexion. Clinically
the use of decreased hip flexion, internal rotation, and/or discomfort with the hip impingement
test has been used to diagnosis FAI. Our results suggest that playing football, especially at the
offensive or defensive line, linebacker, or safety positions may predispose an individual to
developing clinical symptoms of FAI.
Key Words:
Femoroacetabular Impingement: pathological condition involving femoral neck
Osteoarthritis: joint disorder due to aging, wearing, or tearing of joint
Hip Range of Motion: distance the hip joint can move between the flexed and extended position
Hip Flexion: Forward movement of the lower leg in the coronal plane that decreases the hip
angle
Hip Internal Rotation: Rotational movement along the longitudinal axis of the hip joint towards
the midline of the body
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INTRODUCTION
Osteoarthritis in the hip has been known to develop in older populations, resulting in
open surgeries to repair damaged bone and cartilage and in many cases a total hip replacement is
the end result (Ganz, Leunig, Leunig-Ganz, & Harris, 2008). Recently, a new mechanism has
appeared in the literature that has been thought to be a leading cause of osteoarthritis in patients
later in life. It has been proposed that femoroacetabular impingement (FAI) may be a factor
involved in the development of osteoarthritis (Philippon, Stubbs, Schenker, Maxwell, Ganz, &
Leunig, 2007). In fact, a retrospective study of Caucasian cases in the United States suggested
79% of the cases of adult osteoarthritis were associated with FAI (Ganz, Parvizi, Beck, Leunig,
Nötzli, & Siebenrock, 2003). Femoroacetabular impingement results from an abnormal contact
between the neck of the femur and pelvis. Due to this impingement, the individual experiences
changes or pathological conditions in the femoral neck, labrum, and/or acetabulum, resulting in
groin pain and decreased range of motion in the hip (Lavigne, Parvizi, Beck, Siebenrock, Ganz,
&Leunig, 2004). There are two main deformities associated with FAI. The Cam form involves
the femoral head and neck not being perfectly round and having a much larger radius then usual
(Figure 1).
Figure 1. Types of FAI pathologies.
This results in abnormal contact between the rim of the socket and the femoral head. The
Cam form has been mostly found in young athletic males. The Pincer form is another deformity
that is associated with FAI differing from the Cam by the acetabulum over-covering the head of
the femur creating a “pinching” effect (Figure 1). This form is found more frequently in middleaged women involved in athletic activities. It is more common that these two forms are both
found or “mixed” in an impingement with Cam predominance (Corten, Ganz, Chosa, & Leunig,
2011).
Currently found in the literature, the largest group of individuals diagnosed with FAI is
young (average age of 30), physically active adults (Kaplan, Shah, & Youm, 2010). Many
patients who are diagnosed with FAI have histories of participating in athletics that promote
certain movements, especially movements that exaggerate hip internal rotation such as a
goalkeeper’s stance in ice hockey. FAI has been prevalent in sports that have sharp cutting and
sprinting movements, especially common in ice hockey, tennis, martial arts, and soccer (Keogh
& Batt, 2008) due to having movements involving a consistent internal rotation and flexion of
the hip. These movements promote impinging of the femoral neck against the acetabular labrum
(Keogh & Batt, 2008).
In many cases, the onset of FAI begins with groin pain due to overuse or injuries to the
hip. The common thought at this point is that the physically active individual often thinks they
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have “pulled a muscle,” backs off of activity for a few days and continues on with life. After
consulting a physician for the groin pain, FAI is often misdiagnosed as a groin strain, knee or
lumbar spine pathology, ovarian cysts, trochanteric bursitis, and/or abdominal region hernias
(Philippon, Maxwell, Johnston, Schenker, & Briggs, 2007). In many cases this may lead to
weeks or months of incorrect treatment and/or unnecessary and costly surgeries in some cases
(Keogh & Batt, 2008).
It was the intent of this study to investigate the characteristics of the college age (18-23
years of age) intercollegiate athlete and their predisposition to having a deformity (FAI). Due to
their long standing as a physically active individual and playing sport at a competitive level
(collegiate athletics), we hope to gain a better understanding of what type of individual exhibits
clinical signs and symptoms associated with FAI. Thus posing the question, does playing in
competitive athletics potentially contribute to the development or exacerbation of FAI?
METHODS
The Institutional Review Board at UW- Eau Claire provided approval for this study.
Participants were recruited from the University of Wisconsin- Eau Claire’s Intercollegiate
Athletic program and were currently eligible to participate in football. The participants were
contacted through the medical services area in the Department of Intercollegiate Athletics and
asked to participate in this study. 108 male collegiate football players (19.8±1.5 years,
182.4±18.6 cm height, 97.6±21.1 kg weight) participated in this study. During the athletes’ preseason football physical, at the athletic training center on UW – Eau Claire’s campus,
participants were asked to read and sign an informed consent document if they wished to
participate in the study. They then were directed to complete a survey that gathered basic
demographic information, a brief medical history that was relevant to prior hip injuries, and prior
sport/activity participation. Research assistants reviewed the survey for completeness before
allowing the participants to proceed.
After completing the survey, the research assistants, senior athletic training students and
athletic training staff members, administered the physical assessment tests. These students and
staff were specifically trained for these tests and practiced the measurement methods prior to
administering the tests. The researchers took participants’ height and weight in addition to
administering range of motion tests in teams of two to provide a more accurate administration of
the tests. A goniometer was used to measure hip internal rotation by having the patient in a
supine position, flexing the hip and knee to 90°, and rotating the hip inwards passively to the
endpoint of rotation (Ganz et al., 2003). Data was gathered on both hips, regardless of the
participant’s prior health history. Hip flexion range of motion was also tested with a goniometer
with the patient in a supine position and flexing the hip passively to its maximum end range of
motion (Ganz, et al., 2003). Figure 2 displays the layout of the hip internal rotation test. The hip
flexion range of motion test is displayed in Figure 3.
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Figure 2. Hip Internal Rotation Test.
Figure 3. Hip Flexion Test.
These specific tests were measured in passive range of motion. Finally, the research
assistants directed participants in completing a hip impingement and Trendelenburg sign tests
(Nunley, Prather, Hunt, Schoenecker, & Clohisy, 2011).
If participant’s test met specific criteria (< 115° hip flexion, < 15° internal rotation, or
pain with internal rotation) (Ganz et al., 2008) they were recorded as “positive” for exhibiting the
clinical symptoms of FAI.
RESULTS
Descriptive statistics were used to report the characteristics of the population as well as
chi-square analysis to test the proportionality of pathological symptoms and functioning.
Statistical significance was set at p<0.05. Statistical analyses were performed using SPSS
version 18.0 (SPSS Inc.). As shown in Table 1, only the hip flexion and internal rotation
measurements were found to be significant in relation to having clinical signs for FAI.
Table 1. Football players’ results broken down by criteria tested.
p<0.05
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Approximately half of the participants (42.6%) tested positive in the hip flexion tests.
While not as many participants tested positive in regards to hip internal rotation (5.6%), the
findings were found to be significant.
Table 2 breaks down the data collected by football playing position specifically.
Table 2. Results by football playing position.
N= 108
Two positions were found to have a high number of positive cases. Out of 17 offensive
linemen participants, 82.4% met the criteria for the hip flexion test and 17.6% for the hip internal
rotation range of motion. These were the highest percentages found between the nine different
playing positions. Defensive linebackers had the second highest percentages with hip flexion and
hip internal rotation at 81.3% and 12.5% respectively.
Our study provides data that suggests that participating in certain football positions may
present a greater risk of developing the clinical signs of FAI. No significant difference was found
when comparing various other sports included in the data collection (i.e., Woman’s volleyball,
soccer, ice hockey, gymnastics, Men’s ice hockey) to the development of clinical signs of FAI.
Our results suggest that playing the football positions of offensive or defensive line, linebacker,
or safety positions may predispose an individual to developing clinical symptoms of FAI. 11.8%
of defensive linebackers reported having hip pain with the hip impingement test, which was a
much larger percentage when compared to percentages of other positions, though this statistic
was not found to be significant.
DISCUSSION
The principal finding in this study is that clinical FAI symptoms are significantly found
in a population of collegiate football players. Could certain athletic activities be indicators for
populations that have a higher chance of developing clinical symptoms of FAI? This study
partially supports the initial question that participating in football may lead to a higher incidence
of developing FAI. Alongside football, other sports such as hockey and soccer have seen high
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percentages of FAI cases among players, as seen in the literature of surgical case studies (Keogh
& Batt, 2008). These sports involve a lot of cutting and sprinting so is it plausible that these
movements specifically attribute to the development of FAI (Kaplan, Shah, & Youm, 2010).
These questions will remain unanswered until more research has been completed in regards to
the characteristics of FAI.
Our findings and other studies completed on populations affected by FAI, can influence
the way physicians think about diagnosis and treatment of patients complaining of hip/groin
discomfort. One possible stride that could be made in the diagnosis of FAI is early screenings.
Since a correlation has been reported between athletes involved in certain sports, such as
football, pre-screening individuals involved in these sports could identify FAI at an earlier stage
and a younger age. Another finding in this study is that certain football playing positions are
more susceptible to having FAI symptoms, especially the offensive and defensive line. This
could be another factor that could come into question when pre-screening individuals for FAI
characteristics. Certain sports should not only be singled out for pre-screenings, but special
attention should also be paid to specific playing positions. More research focusing on playing
positions most affected by FAI, could assist in developing specific criteria that can be established
for precisely which sports and positions could be more prone to this pathology.
If FAI is not caught early enough, there is a higher probability that the individual affected could
be faced with having osteoarthritis and possibly needing a total hip replacement later in life,
potentially by 40-50 years of age. This open surgery is highly invasive and has many physical
costs such as loss of movement and in many cases loss of activity (Philippon, Schenker, Briggs,
& Kuppersmith, 2007). Instead, it may benefit the active lifestyle of a younger athlete to be prescreened for FAI and then have corrections through arthroscopic surgery. This surgery is minor
compared to a total hip replacement that may be needed down the road for the athlete (Bedi et
al., 2011). This type of surgery will allow competitive level athletes to return to a high level of
performance in a minimal amount of time (Philippon, Schenker, Briggs, & Kuppersmith, 2007).
This study had various limitations. First, the population was limited to one university and sport
season. It would be beneficial to obtain a larger sample size with a varied demographic. This
would allow data to be more accurate to the actual population of collegiate football players.
Another limitation was that we only had a few positive cases of FAI related symptoms. This is
also due to the low number of participants in the study. This could have affected results because
the ratio of positive cases to negative FAI cases may not be accurately represented in a sample
population of this size. It would be beneficial for future studies on FAI to include a larger sample
population focusing on other sports as well. The more information gained by studies such as this
one, the greater the chance of FAI symptoms being recognized at a younger age. This can
hopefully save patients some money that would have been used for total hip replacements down
the road and can let them continue their active lifestyles for a much longer period of time.
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