summary of peer reviewed article

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 specifically the Abstract, Introduction, Discussion, and Conclusion – and write a summary based off of those specific sections in this article. 

3 paragraphs for this discussion post will be efficient. 3 paragraph SUMMARY: 1) Define research 2) methodology 3) Results/conclusion 

ABSTRACT
Background: The knee is susceptible to injury during cycling due to the repetitive nature of the activity while gen-
erating torque on the pedal. Knee pain is the most common overuse related injury reported by cyclists, and intrinsic
and extrinsic factors can contribute to the development of knee pain.

Purpose: Due to the potential for various knee injuries, this purpose of this systematic review of the literature was to
determine the association between biomechanical factors and knee injury risk in cyclists.

Study Design: Systematic review of the literature

Methods: Literature searches were performed using CINAHL, Ovid, PubMed, Scopus and SPORTDiscus. Quality of
studies was assessed using the Downs and Black Scale for non-randomized trials.

Results: Fourteen papers were identified that met inclusion and exclusion criteria. Only four studies included cyclists
with knee pain. Studies were small with sample sizes ranging from 9-24 participants, and were of low to moderate
quality. Biomechanical factors that may impact knee pain include cadence, power output, crank length, saddle fore/
aft position, saddle height, and foot position. Changing these factors may lead to differing effects for cyclists who
experience knee pain based on specific anatomical location.

Conclusion: Changes in cycling parameters or positioning on the bicycle can impact movement, forces, and muscle
activity around the knee. While studies show differences across some of the extrinsic factors included in this review,
there is a lack of direct association between parameters/positioning on the cycle and knee injury risk due to the
limited studies examining cyclists with and without pain or injury. The results of this review can provide guidance to
professionals treating cyclists with knee pain, but more research is needed.

Level of Evidence: 3a

Key Words: Biomechanics, cycling, knee injury, knee pain, overuse

I
J
S
P

T
SYSTEMATIC REVIEW

THE INFLUENCE OF EXTRINSIC FACTORS ON KNEE

BIOMECHANICS DURING CYCLING: A SYSTEMATIC

REVIEW OF THE LITERATURE

Therese E. Johnston, PT, PhD, MBA1
Tiara A. Baskins, DPT1
Rachael V. Koppel, DPT1
Samuel A. Oliver, DPT1
Donald J. Stieber, DPT1
Lisa T. Hoglund, PT, PhD, OCS1

1 Department of Physical Therapy, Jefferson College of Health
Professions, Philadelphia, PA, USA

CORRESPONDING AUTHOR
Therese E. Johnston, PT, PhD, MBA
Department of Physical Therapy, Jefferson
College of Health Professions
Jefferson (Philadelphia University + Thomas
Jefferson University)
901 Walnut Street, Room 515, Philadelphia,
PA 19107
T 215-503-6033, F 215-503-3499
E-mail: therese.johnston@jefferson.edu

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1023
DOI: 10.16603/ijspt20171023

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1024

INTRODUCTION
With the increase in recreational and competitive
cycling, cyclists are experiencing more overuse inju-
ries related to repetitive loading.1 Both intrinsic and
extrinsic factors contribute to injury.1 Intrinsic fac-
tors are inherent to the cyclist and include fitness
level as well as anatomical alignment of the lower
extremities.1 Extrinsic factors are generally asso-
ciated with factors external to the cyclist such as
equipment, riding technique, and training.1

The knee is the most common joint impacted by
cycling overuse injuries in recreational and pro-
fessional cyclists.1,2 Knee pain is reported to affect
40-60% of recreational cyclists and 36-62% of profes-
sional cyclists. 1,3,4 Anterior knee pain is the most
common, which is likely due to patellofemoral pain,
patellar tendinopathy, or quadriceps tendinopa-
thy.1,3-5 Factors that may cause anterior knee pain
include increased pressure due to hill climbing,
heavy workloads, increased training, altered patel-
lar tracking, or by a combination of factors.1,3,4 Many
risk factors can contribute to the problem such
as altered patellar position, decreased flexibility,
increased quadriceps (Q) angle, muscle imbalances,
and various limb torsional and foot deformities.1,6
In a review article, Johnston reported that cycling
cadence and workload impact moments around
the knee, which may contribute to knee injury at
higher effort levels.7 Increasing knee flexion angle
can increase forces impacting the knee8 while co-
contraction of the knee flexors and extensors can
decrease them.9 Thus the interaction of these vari-
ables as well as power output and cycling duration
may be important in understanding cyclists who are
at greater risk of injury due to loading.

Several knee structures are potentially at risk for over-
use injury with cycling due to intrinsic and extrinsic
factors. Patellofemoral pain (PFP) is one of the most
common causes of knee pain in cyclists, resulting
in anterior knee pain.5 Female gender is a risk fac-
tor for PFP,10 and PFP is more common in female
cyclists.11 An additional risk factor is reduced quadri-
ceps strength,10 which may cause the greatest preva-
lence of PFP during preseason training in cyclists.4
Additional associated factors with PFP in cyclists
include excessive varus knee moments during the
power stroke,12 excessive valgus knee alignment,5

repetitive loading of the patella,13 weak gluteal mus-
cles,5 increased Q angles,11 excessive patellar lat-
eral tilt,5 and excessive foot pronation.5 Patellar and
quadriceps tendinopathies are additional causes of
anterior knee pain in cyclists, 5 which are caused by
chronic repetitive overload of tendons during quadri-
ceps contractions.14,15 Iliotibial band (ITB) syndrome
is the most common cause of lateral knee pain in
cyclists.2 Proposed mechanisms for ITB syndrome
are compression of fat beneath the ITB at the lateral
femoral epicondyle or friction of the ITB as it moves
across the lateral femoral epicondyle during repeti-
tive knee flexion and extension.2,11,16 When the knee
reaches 20-30° of flexion, the ITB passes over the
lateral femoral epicondyle,17,18 creating an impinge-
ment zone for fat and an adventitial bursa.2,5,11 ITB
syndrome is likely caused by increased tibial inter-
nal rotation, ITB tightness, inward pointing of toes
on the pedals, increased hip adduction, a bicycle
saddle position that is too high, and rapid increase in
mileage.1,2,5,16,19 Medial knee injuries seen in cyclists
include medial collateral ligament bursitis, plica syn-
drome, pes anserine syndrome and medial meniscus
tear.2 Plica syndrome is characterized by pain, snap-
ping or clicking sensations as inflamed remnants of
synovial tissue impinge against the anterior medial
femoral condyle as the knee flexes and extends.2,20
Medial meniscus tear is least likely to occur in
cyclists, but can be symptomatic when rotating the
leg to release the shoe from the pedal.2 The poste-
rior knee is the least commonly injured and may be
attributed to biceps femoris tendinopathy presenting
posterolaterally.2 The etiology of biceps femoris ten-
dinopathy is chronic overload of the hamstring mus-
cles and tendons, and may be due to tight hamstrings
or an excessively high saddle.21

Due to the potential for various knee injuries, this
purpose of this systematic review of the literature was
to determine the association between biomechanical
factors and knee injury risk in cyclists. To accom-
plish this goal, biomechanical studies that examined
extrinsic factors including kinematics, kinetics, and/
or muscle activity under various cycling conditions
and cycle component settings were included.

METHODS
Search Strategy: An initial literature search was
performed in August of 2015 using CINAHL, Ovid,

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1025

PubMed, Scopus & SPORTDiscus databases. Key
terms used in the search included knee injuries,
knee pain, cycling, cyclist, biomechanics, and over-
use. All keywords were compiled and searched
using AND/OR to further refine the search. Key
words were used to screen titles that best addressed
the research question. A second search using the
same search terms and databases was performed in
March of 2017 to locate additional articles published
between August of 2015 and March of 2017.

Selection Criteria: Of the 46 articles selected, abstracts
were screened based on the inclusion criteria of
evaluating extrinsic biomechanical factors associated
with the knee in cyclists. Studies were required to
include measurement of one or more of the following
at the knee during cycling: kinematics, kinetics, and
muscle activity. Studies were excluded if they were
not published in English, focused on injury in other
areas of the body, or evaluated traumatic injury. The
studies included were comparison or cross sectional.

Data Collection: Five reviewers evaluated the final
studies after applying inclusion/exclusion criteria
from full text articles. Each study was read and eval-
uated by two reviewers. Articles were graded using
the Downs & Black scale for assessment of meth-
odological quality and risk of bias.22 The Downs &
Black scale is considered a valid and reliable check-
list for non-randomized studies and was deemed
appropriate due to the observational nature of the
studies.22,23 Data extracted from articles included
population, variables measured, results, and conclu-
sions (Table 1).

RESULTS
Study Selection: Of the 72 studies found across the
two searches, 14 were deemed eligible based on
inclusion criteria (Figure 1). Studies were overall
small with sample sizes ranging from 9-24 partici-
pants, with a total of 239 participants across studies.

Study Characteristics: Studies that reported gender
included more male than female participants. Stud-
ies included adults aged 19 to over 50 years. Eleven
studies were within-participant designs with one
study including participants with knee pain24 and
10 including participants without injury.12,25-33 Three
studies34-36 compared participants with and without

pain. Participants were described as competitive
cyclists,12,28,29 amateur cyclists,32 experienced24-26 or
trained cyclists,27 recreational cyclists,30,31,34 non-
cyclists,33,36 or cyclists without further description.35

Assessment of Included Studies: Ten of the 14 stud-
ies had sample sizes of less than 20 participants.
Downs and Black scores ranged from 3 to 13 (out of
27) with a median score of 10 (Table 1). Study qual-
ity was categorized according to percentage of the
possible Downs and Black score as follows: low (≤
33.3%), moderate (33.4% – 66.7%), and high quality
(≥ 66.8%).23 Therefore, the included studies were of
low to moderate quality using this scale.23 No blind-
ing of assessors occurred in any comparison studies.

Methodology and Outcomes Measured: Methodology
and outcomes measured varied across studies (Table
1). Knee kinematics with or without assessment
of other joints were main outcomes assessed in 10
studies using 2D or 3D motion capture.24,28-36 Knee
kinematics were primarily measured in the sagit-
tal plane, but three studies also measured kinemat-
ics in the coronal plane.24,30,36 Knee kinetics with or
without assessment of other joints were main out-
come measures in 12 studies with different mea-
sures examined, including joint power,25-27 muscle/
joint moments,12,27,29,30,34,36 patellofemoral compres-
sive forces,28,33,34 tibiofemoral compressive and
shear forces,28,33,34 pedal forces/pedal force effective-
ness,29,31,33,34,36 and crank torque.32 Moments around
the knee were primarily measured in the sagittal
plane, but four studies also examined moments
in the coronal plane.12,24,30,36 Two studies measured
muscle activity around the knee using electromyog-
raphy (EMG),12,35 and one study assessed pain.36

Experimental Conditions: Studies manipulated several
conditions to examine effects at the knee, including
cadence,25,27,30 power output,26,30,32 crank length,25,27,32
saddle fore/aft position,28 saddle height,29,31,33,34 and
foot position.12,36 Participants used their own cycles
mounted on a trainer,24,28,35 a type of cycle ergom-
eter,12,25-27,29,30,32-34,36 or a standard cycle on a trainer.31

Cadence and Power Effects: Increasing cadence led to
increased knee range of motion (ROM),27 increased
anterior and vertical pedal reaction forces,30 and
increased knee flexion moments.30 As cycling
power output increased, greater knee extension and

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1026

Table 1. Study characteristics, results, and Downs and Black scores.

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1027

Table 1. Study characteristics, results, and Downs and Black scores. (continued)

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1028

Table 1. Study characteristics, results, and Downs and Black scores. (continued)

abduction moments were seen.30 Related to these
increases, relative knee flexion power increased
while extension decreased with increasing power
output.26 Interestingly, hip extension power was
reported to be dominant in power production, but
relative hip extension power did not change with
increased power output.26 Increased knee vertical
and medial pedal reaction forces were seen with
increasing power output.30

Bicycle Setting Effects: In two studies, Barratt et al.
examined power25,27 and muscle moments27 at five
different crank lengths at a cadence of 120 rpm and
a cadence optimized to provide maximum power.
They reported that crank length had no effect on
power at joints, except for greater power at the short-
est crank length of 150mm compared to the longest
of 190mm at 120 rpm;25 thus showing a combined
effect of crank and cadence.25 In another study,
knee extension moments and power decreased,
and hip extension power increased as crank length
increased.27 In contrast, Ferrer-Roca et al.32 reported
increased crank length led to increased torque
around joints; however the range of crank lengths
used was much smaller (10 mm)32 than in Barratt et
al. (40 mm).25,27

Bini et al.28 manipulated saddle fore/aft position and
reported increased knee flexion angles of 22-36%
and decreased tibiofemoral anterior shear forces of
26% with the saddle at the most forward position
compared to the most backward position. No differ-
ences were seen across positions in patellofemoral

Records iden�fied through CINAHL,
OVID, PubMed, Scopus,

SportDiscus
(n = 61)

Records a�er duplicates removed
(n = 46)

Titles screened
(n = 46)

Titles excluded a�er review
(n = 15)

Abstracts screened
(n = 31)

Abstracts excluded a�er
review

(n = 13)

Studies included in review
(n = 14)

Full-text ar�cles assessed for
eligibility
(n = 18)

Full text ar�cles excluded
a�er review due to not

mee�ng inclusion criteria
(n =10)

New ar�cles found from updated
search a�er screen of full text

(n = 11)

Full text ar�cles excluded
a�er review

(n =5)

Ar�cles included from first search
a�er full text screen

(n = 8)

Figure 1. PRISMA Flow Diagram.

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1029

and tibiofemoral compressive forces.28 Three stud-
ies examined various saddle heights,29,33,34 one of
which being a height considered optimal, which
was defined as the position that achieved 25-30° of
knee flexion at bottom dead center.29 Bini et al.34
examined four different saddle heights and found
increased tibiofemoral anterior shear forces at high
and optimal compared to low saddle height34 and
large differences in knee angle across conditions in
recreational cyclists. There were no differences for
patellofemoral or tibiofemoral compressive forces
across seat heights and no differences seen between
cyclists with and without knee pain.34 In competitive
cyclists, they found increased force effectiveness for
road cyclists at optimal saddle height, and increased
mean knee flexion angles at low and preferred com-
pared to high and optimal saddle heights for road
cyclists and triathletes.29 Interestingly, Farrell et
al.31 reported that while saddle height was set in the
optimal position statically, knee flexion seen while
cycling was greater due to lateral movement of the
pelvis in recreational cyclists, which may decrease
risk of ITB impingement.31 Finally, Tamborindeguy
and Bini33 set saddle height based on cyclists’ anthro-
pometrics and found no differences in peak tibio-
femoral compressive/anterior shear components
across three slightly different saddle heights based
on percentages of floor-greater trochanter heights of
97%, 100%, and 103%.

Two studies examined effects of foot position on
knee forces. For participants with osteoarthritis
(OA) with and without pain, decreased knee adduc-
tion angles of 2.7° and 3.2° were seen with wedges
placed to increase the toe-in angle by 5° and 10°,
respectively; yet no changes were seen in knee
abduction moments and vertical pedal reaction
forces increased.36 Ankle eversion of 10° was found
to decrease knee peak varus moments by 55% and
peak internal axial moments by 53% and to increase
activation ratio of the vastus medialis to vastus late-
ralis (r = -0.23).12 Thus eversion of the foot may
decrease risks for PFP.12

Muscle Temporal Activation and Kinematics: Two stud-
ies compared temporal muscle activation patterns
and kinematics between cyclists with and with-
out pain without manipulating cycling conditions.
Dieter et al.35 reported differences in muscle activity

patterns for cyclists with and without PFP. In cyclists
with PFP, offset of the vastus medialis occurred 22 ±
23 ms sooner than the vastus lateralis, onset of the
biceps femoris occurred 111 ± 78 ms sooner than
the semitendinosus, and the semitendinosus had
overall decreased activation compared to cyclists
without pain.35 Bailey et al.24 reported differences in
knee and ankle angular positions between cyclists
with a history of anterior knee pain or patellar tendi-
nitis and uninjured cyclists. The previously injured
group had lower peak knee adduction angles and
increased ankle dorsiflexion angles. No differences
were found for peak knee flexion angles.24

DISCUSSION
Cycling parameters (i.e., cadence and power out-
put) and bicycle fit settings have differing effects on
kinematics, kinetics, and muscle activity around the
knee. Few studies compared cyclists with and with-
out knee pain, so injury risk can only be surmised
based on the results of biomechanical studies that
examine cyclists without injury or pain. There is also
a lack of longitudinal studies to assess the effects of
altering parameters on knee injury and pain. Thus,
causation cannot be determined.

Studies examining cycling kinetics indicate that vari-
ous stresses are imparted on the knee based on a vari-
ety of kinetic variables. Vertical and anterior pedal
reaction forces increase at higher cadences,30 and
vertical and medial pedal reaction forces increase at
higher power outputs.30 Tibiofemoral peak anterior
shear forces were found to be increased at higher
saddle heights,34 and ankle inversion increased peak
vertical forces.12 These findings are in partial agree-
ment with an earlier study by Ericson and Nisell,37
which reported that higher saddle heights signifi-
cantly increased tibiofemoral anterior shear forces,
but decreased tibiofemoral compressive forces. The
findings of the studies in this systematic review
and earlier studies have implications for loading
of the knee joint during cycling and suggest that
lower cadences, lower workloads, a higher saddle
height, and foot eversion might be preferred for
cyclists with knee pain due to tibiofemoral compres-
sive joint loading, such as with medial tibiofemoral
OA. In contrast, cyclists with anterior cruciate liga-
ment injury or reconstruction may benefit from a

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1030

lower saddle height and lower cadences.30,34,37 How-
ever, force effectiveness, a measure of force output
in relation to angle of force application, may be
decreased with these settings,29 and thus the effects
of combining these conditions is unknown. The
effect of crank length due to loading is more diffi-
cult to interpret as a shorter crank length at a higher
cadence increases power output,25 yet increased
crank lengths may shift more of the power produc-
tion from the knee extensors to the hip extensors.27
When comparing the moments around the knee to
other activities such as walking, jogging, and stair
climbing, the extension and flexion moments are
generally smaller when cycling at 120 Watts. At 240
Watts, the loads were similar to the other activities.38
Knee injuries are the most commonly reported inju-
ries in cyclists, thus it may be the combined effects
of workload, cadence, and positioning on the cycle
that contribute to injury.

Shear forces are another concern in cyclists, par-
ticularly possible injury to the anterior cruciate
ligament (ACL) or after an ACL reconstruction. Tib-
iofemoral anterior shear forces may decrease with a
more forward28 or lower saddle position,34 decreas-
ing potential strain on the ACL. However, studies
reported low in vivo ACL strain39 and low anterior
tibiofemoral shear force37 during cycling. Fleming et
al.39 reported that strain on the ACL during cycling
was approximately 1.7%, and did not change sig-
nificantly with alteration of cadence or power level.
Strain on the ACL during cycling was low compared
to 3.6% while squatting and 2.8% while extending
the knee from flexion.39 Strong contraction of the
hamstrings during the second half of the power
phase may minimize ACL strain.40 Posterior pull of
the hamstrings on the tibia when the crank angle
is 180° from top dead center may limit ACL strain
as the knee approaches its least flexed position of
37°,41 an angle which is within the range of great-
est ACL strain during activities, 0° – 50° flexion.42
While shear forces on the ACL during cycling appear
to be low, more research is needed to examine shear
forces on the posterior cruciate ligament and patella
during cycling. Thus, cyclists with anterior cruciate
ligament injury or reconstruction may benefit from
a lower saddle height or more forward saddle posi-
tion.28,34 as well as a lower cadence.30

Medial and lateral regions of the knee are also sus-
ceptible to injury. Coronal plane forces are affected
by foot position, with eversion lowering peak varus
and internal axial moments and increasing vastus
medialis activation compared to inversion.12 For
people with medial knee OA, rotating the shank
to increase toe-in angle reduced peak knee adduc-
tion angles, with no impact on peak knee abduction
moments.36 Gardner et al.36 hypothesized that an
alignment change with increased toe-in foot posi-
tion would decrease the frontal plane moment arm
of the pedal reaction force, which would decrease
knee abduction moments. As competitive cyclists
and people with knee OA differ in knee alignment,
findings may be specific to these populations. One
study examined the impact of saddle height on ITB
syndrome and reported that a lower saddle height
that increased minimum knee flexion angle to
greater than 30° kept the ITB out of the impinge-
ment zone.31 For cyclists at risk for ITB pain, a lower
seat height may also be desirable by reducing com-
pensatory lateral pelvic motion31 that can increase
stress to the ITB. Overall, more research is needed
to better understand the effects of cycling on the
medial and lateral regions of the knee.

Few studies have examined PFP in cyclists specifi-
cally, which is surprising due to the prevalence of
anterior knee pain in cyclists.2 One study reported
differences in muscle activation between cyclists
with and without PFP.35 Although no differences
were found between groups for vastus medialis onset
times, the slower contraction offset time of vastus
lateralis relative to vastus medialis in the PFP cyclist
group may be associated with lateral patellar mal-
tracking.35 These findings are consistent with a sys-
tematic review that did not find a difference in vastus
medialis and vastus lateralis contraction onset in per-
sons with PFP, but reported significant variability in
muscle activation ratio.43 Dieter et al.35 also reported
earlier contraction onset and later offset time of the
biceps femoris relative to the semitendinosus in the
PFP group compared to controls.35 These changes
may result in increased tibial external rotation, with
a resultant increase in the dynamic Q angle and
potentially increased lateral patellofemoral joint
stress.44,45 As the hamstrings are active longer than
the quadriceps during cycling,21 altered hamstring

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1031

activation may be more critical to development of
PFP in cyclists compared to vasti activation. How-
ever, it is unknown if altered muscle activation is
compensatory to or a cause of PFP. Altered coronal
plane knee position may be associated with PFP as
reduced knee adduction angles, that is, a more val-
gus position, are seen in cyclists with anterior knee
pain or patellar tendonitis.24 Studies in this system-
atic review that examined the impact of saddle posi-
tion on patellofemoral compressive forces did not
find significant differences.28,33 In contrast, an earlier
study by Ericson and Nisell8 reported that a lower
saddle increased patellofemoral joint compressive
forces. Although increased knee flexion from a lower
saddle position would increase patellofemoral joint
reaction force,46 patellofemoral joint cartilage stress
does not increase linearly with increasing knee
flexion from 0° to 90°.47 Patellofemoral joint stress
increases to a lesser degree than patellofemoral joint
reaction force with increasing knee flexion due to
increased patellofemoral joint contact surface area.47
Tamborindeguy and Bini33 found the highest patel-
lofemoral compressive force occurred with the knee
at approximately 75°-80°. Thus, patellofemoral joint
stress may be minimized during cycling by greater
patellofemoral joint contact area at knee joint posi-
tions which have high patellofemoral joint reaction
forces.47 PFP in cyclists may not be related to high
joint stress, but rather secondary to frequent patello-
femoral joint loading from repetitive knee extension.
This repetitive loading could cause supraphysiologic
loading of osseous and non-osseous structures poten-
tially causing loss of tissue homeostasis and PFP.48,49
More research is needed to understand patellofemo-
ral compressive and shear forces and how they are
associated with risk of injury.

In the articles in this systemic review, no issues spe-
cific to the posterior knee were discussed. Elmer
et al.26 reported that knee flexion power increased
relative to extension power as overall power out-
put increased,26 which may have implications for
biceps femoris tendinopathy.2 Interestingly, Dieter
et al.35 found that biceps femoris muscle activation
occurred prior to semitendinosus onset in cyclists
with PFP, unlike those without this anterior pain
condition. More research is needed on posterior
knee pain in cyclists.

There are several limitations of this systematic
review. Studies differed considerably in methodol-
ogy, making qualitative or quantitative compari-
sons challenging. It is also difficult to make strong
recommendations as far as the amount of change
needed to decrease injury risk as studies vary in the
magnitude of changes in cycling parameters and
bicycle settings. Bini et al.34 reported that even a
5% difference in saddle height can affect knee joint
kinematics by 35% and joint moments by 16%;34
yet it is unknown how these differences then trans-
late into injury risk. There is also the lack of direct
association between parameters/positioning on the
cycle and injury due to limited studies examining
cyclists with and without pain or injury and a lack
of longitudinal studies. More research is needed
to establish clear links and recommendations by
manipulating parameters based on the available lit-
erature and knowledge of biomechanics impacting
specific areas of the knee. Longer term effects on
pain, performance, and participation should then
be assessed. Another limitation is the inclusion of
2D measurements in some studies. 2D data capture
can be misleading as movement outside of the sag-
ittal plane impacts how each joint is visualized on
a 2D image. In addition, 3D kinetic measurements
are needed to fully understand the effects on the
knee in all three planes.

CONCLUSIONS
The results of this systematic review indicate that
changes in cycling parameters or positioning on the
bicycle can impact movement, forces, and muscle
activity around the knee. While studies showed dif-
ferences across some of the extrinsic factors, there
is a lack of direct association between parameters/
positioning on the cycle and knee injury. Despite
the lack of this clear association, the results of this
systematic review can provide guidance to profes-
sionals treating cyclists with knee pain. The liter-
ature provides important information about how
biomechanical factors and positioning on the bicy-
cle can increase or decrease stress in specific areas
of the knee joint. Further research is needed with
larger samples of cyclists with including those with-
out knee pain to better understand direct relation-
ships between these variables and knee pain during
cycling.

The International Journal of Sports Physical Therapy | Volume 12, Number 7 | December 2017 | Page 1032

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