Evidence based concepts for prevention of knee and ACL injuries. 2017 guidelines of the ligament committee of the German Knee Society (DKG)

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Arch Orthop Trauma Surg 
DOI 10.1007/s00402-017-2809-5
ARTHROSCOPY AND SPORTS MEDICINE
Evidence‑based concepts for prevention of knee and ACL injuries. 
2017 guidelines of the ligament committee of the German Knee 
Society (DKG)
Julian Mehl1 · Theresa Diermeier1 · Elmar Herbst1 · Andreas B. Imhoff1 · 
Thomas Stoffels2 · Thore Zantop3 · Wolf Petersen4 · Andrea Achtnich1 
Received: 22 February 2017 
© Springer-Verlag GmbH Germany 2017
warm-up exercises and are focusing on muscle strength, bal-
ance, and proprioception, as well as running and flexibility. 
It is reported that these training programs can reduce the 
incidence of knee injuries by up to 27% and ACL injuries 
by up to 51%.
Conclusions Screening, identification, and correction of 
endangering movement patterns like the dynamic valgus 
are the first crucial steps in order to prevent knee and ACL 
injuries in athletes. Furthermore, jumping, running and flex-
ibility exercises as well as balance and strength training are 
proven to reduce the incidence of these injuries and should, 
therefore, be integrated into the regular warm up program. 
Appropriate complete prevention programs are freely acces-
sible via the Internet and should be adapted to the specific 
sport disciplines.
Keywords Injury risk · Knee · ACL · Prevention · 
Screening · Valgus · Core stability · Proprioception
Introduction
Anterior cruciate ligament (ACL) tears are one of the most 
frequent injuries of the knee with an estimated incidence of 
1:3500 [34, 44]. Due to the typical jumping and stop-and-go 
movements ACL tears are relatively common in ball sports. 
However, knee injuries are also frequent in other sports like 
alpine skiing, judo, and field hockey.
The ACL has an important function for knee kinematics, 
and ACL tears result in serious consequences for the con-
cerned athlete. Instability of the knee joint might directly 
reduce the athlete’s performance. In the long term chronic 
instability might lead to repetitive subluxations with conse-
quently meniscal and cartilage lesions [51–53]. Therefore, 
Abstract 
Introduction Knee injuries and especially anterior cruciate 
ligament (ACL) tears are frequent in athletes. Therefore, pri-
mary and secondary prevention of sports-related lower limb 
injuries is an ongoing topic of interest. The aim of present 
study was to establish guidelines for the prevention of knee 
and ACL injuries on the basis of evidence-based concepts 
represented in current literature.
Methods A comprehensive literature review regarding pre-
vention programs for knee and ACL injuries was conducted.
Results Several modifiable and non-modifiable risk fac-
tors for knee injuries in athletes have been reported in lit-
erature. Referring to the ACL, specific injury mechanisms 
have been identified and are well understood. In particular, 
it has been demonstrated that dynamic valgus is one of the 
most important modifiable risk factors. Simple tests like the 
drop jump test have shown their efficacy in screening and 
detecting athletes at risk. There is only few evidence for 
the preventive effect on knee and ACL injuries by single 
exercises. However, in order to prevent or correct endanger-
ing movement patterns including dynamic valgus, several 
complex prevention programs have been developed in the 
past. These prevention programs are included in standard 
 * Andrea Achtnich 
 a.achtnich@tum.de
1 Department of Orthopaedic Sports Medicine, Klinikum 
Rechts der Isar, TU Munich, Ismaninger Str. 22, 
81675 Munich, Germany
2 Department of Trauma and Orthopaedic Surgery, 
Unfallkrankenhaus Marzahn, Berlin, Germany
3 Sporthopaedicum Straubing, Straubing, Germany
4 Department of Orthopaedic and Trauma Surgery, 
Martin-Luther-Krankenhaus, Berlin, Germany
 Arch Orthop Trauma Surg
1 3
the incidence of osteoarthritis in athletes with an ACL tear 
is significantly increased [40].
Reconstruction of the ACL decreases the risk of osteoar-
thritis [2]; nevertheless, only 50% of athletes return to their 
pre-injury activity level, which frequently leads to an early 
end of the athlete’s career [6]. It is also alarming that 7–24% 
of patients with ACL reconstruction suffer an ACL tear of 
the contralateral knee [45, 55]. For these reasons primary 
and secondary prevention of knee injuries is a topic of cur-
rent interest.
In the past years various strategies for prevention of ACL 
tears have been developed including following key points 
[18]:
1. Education about typical injury mechanisms and poten-
tial modifications of endangering movements,
2. exercises to improve balance and proprioception,
3. neuromuscular training for inter- and intramuscular 
coordination,
4. invigoration of the ischiocrural and hip stabilizing mus-
cles, and
5. running exercises.
These strategies were summarized in special prevention 
programs (e.g., Sportsmetrics, Prevent Injury and Enhance 
Performance PEP, Knee Ligament Injury Prevention Pro-
gram, FIFA 11) [4]. A recent meta-analysis found a reduc-
tion of both knee injuries in general and ACL tears by 27 
and 51%, respectively, for patients, who participate in such 
programs [18].
The aim of this article was to summarize and analyze 
evidence-based concepts for prevention of knee and ACL 
injuries. On the basis of these data the ligament commit-
tee of the German Knee Society (DKG) wants to provide 
guidelines in order to reduce the incidence of knee and ACL 
injuries in athletes. These recommendations are directed to 
clinicians, physical therapists, athletes’ coaches, and to the 
athletes themselves.
Methods for guideline development
The present study was conducted on behalf of the ligament 
committee of the German Knee Society (DKG). All above-
mentioned authors are members of the committee and were 
involved in the development of the literature search strategy 
according to a general consensus process as well as in the 
internal review process.
The first part of this article gives a short overview of 
current aspects of injury mechanisms and the assessment 
of risk factors for knee and ACL injuries, while the main 
part discusses different concepts for injury prevention. 
For this purpose literature was searched for studies, which 
present preventive exercises or programs and investigate 
their influence on the incidence of knee and ACL injuries 
in athletes.
The following were the key questions that should be 
answered by present study:
1. What are the typical injury mechanisms and risk factors 
for knee and ACL injuries in athletes?
2. Is there evidence for exercises or programs reducing the 
incidence of knee and ACL injuries in athletes?
3. How can these programs be integrated in the regular 
training?
The recommendations given at the end of this article 
have been confirmed by all authors unanimously.
Injury mechanisms and assessment of risk factors
Injury mechanism
Video analyses of ACL tears revealed new details about 
the injury mechanism [9, 63]. According to these studies, 
in 72–95% of the cases, ACL ruptures occur during non-
contact situations [9, 45, 46]. The most dangerous situa-
tions for ball sports are as follows:
1. landing after a jump,
2. abrupt stopping, and
3. sudden direction change including rotary knee motion 
[49, 63].
At the same time the knee is only slightly bended 
(5°–25° knee flexion) and in a valgus position. In such sit-
uations, the in situ forces within the ACL increase remark-
ably. In addition it could also cause an impingement of the 
ACL against the lateral femoral condyle. Most athletes 
report from a planted foot at the moment of injury. Further, 
usually the body’s center of gravity is behind of that of 
the knee. In this position the associated contraction of the 
quadriceps femoris muscle results in an anterior transla-
tionof the tibia with high tension to the ACL. Due to an 
inappropriate lever arm, the ischiocrural muscles cannot 
sufficiently protect the ACL against this anteriorly directed 
force. In addition to that, the hip needs to be flexed in 
order to maintain the balance, which forces the quadriceps 
femoris muscle to further contract. By means of surface 
EMG Colby et al. [12] could demonstrate that this move-
ment is connected with high activation of the quadriceps 
femoris muscle, whereas the activity of the ischiocrural 
muscles is lower [12].
Arch Orthop Trauma Surg 
1 3
Athletes at risk
The risk factors for injuries of the knee and in particular 
the ACL are summarized in Table 1 [3, 52, 57]. Common 
non-modifiable risk factors ACL re-ruptures are age and 
gender. Patients under 20 years and female patients have a 
significantly higher risk for ACL re-ruptures [19, 39]. Also 
generalized ligamentous laxity is mentioned as one risk fac-
tor [3]. Modifiable risk factors are kind of sports, hormone 
status, and neuromuscular control.
Sports at risk are soccer, basketball, handball, and alpine 
skiing [3]. Several studies could also show an elevated injury 
risk for females without contraception in the pre-ovulatory 
phase [3].
With regards to prevention programs, neuromuscular risk 
factors are of major interest. Various studies could show 
associated neuromuscular risk factors in athletes [3, 29, 30, 
32]. Especially quadriceps femoris muscle dominance, weak 
knee flexors, and the dynamic valgus-position with defi-
ciency in hip and core stability are of importance. It has been 
observed that in athletes at risk, activation of the quadriceps 
femoris muscle occurs earlier than for the protective flexors 
(hamstring muscles) [32].
Furthermore, athletes at risk show general movement pat-
terns similar to the knee position identified during injury 
mechanism analyses: knee valgus (frontal plane) and low 
flexion angles with the center of gravity behind the knee 
(sagittal plane). This valgus knee position is also termed as 
dynamic valgus [3, 29, 57].
In principle, the harmful valgus drift right after a one-
legged landing- or stabilization phase- could occur due to 
decreased hip and core muscle strength with consecutive 
lateral tilting of the hip to the contralateral side, extended 
eversion of the lower ankle, missing coordination, and pro-
prioceptive skills or by any combination of the aforemen-
tioned mechanisms. In athletes at risk proprioceptive defi-
ciencies in core control and strength deficits of the external 
rotators and abductors of the hip could be verified [36, 70]. 
The dynamic valgus could also arise in the distal part of the 
ankle (eversion) and foot (external rotation) [56]. Another 
risk factor in these athletes is an extended “one-leg-domi-
nance” [29].
These movement patterns are more common in female 
athletes [29]. Micromotion studies could demonstrate that 
landing position is more upright in women compared to men 
with a less flexed knee and hip. “One-leg dominance” and 
predominance of strength of the quadriceps femoris muscle 
is also a typical female phenomenon. Moreover, female ath-
letes have an increased valgus position of their knees and 
deficiencies in hip and core stability.
Screening tests
Prevention programs are expensive and, therefore, in the past 
years several tests were developed to identify athletes at risk. 
The main focus of these tests is to detect functional valgus 
position of the knees.
The “Drop Jump Screening Test” is one of the most com-
mon tests [30, 47]. It consists of a vertical jump from a box, 
in which the landing position is analyzed with a video cam-
era (Fig. 1). The frontal projection angle or the distances 
between both knees and ankles could be measured (knee 
distance < ankle distance = dynamic valgus). During such 
landing situations the knee sustains the most uncontrolled 
movement [47].
Minzner et  al. [43] demonstrated a good correlation 
between the relation of the distances of knee and ankle and 
two- or three-dimensional video analyses. Noyes et al. [47] 
showed that this test is also useful to evaluate the success or 
progression of training focused on the correction of dynamic 
valgus knee position. In this study the distance between the 
two knees in female athletes before training was 23 ± 8 cm. 
After a neuromuscular prevention program the knee distance 
was increased to 29 ± 8 cm was, therefore, able to reduce 
the dynamic valgus.
Hewett et al. [30] evaluated the “Drop Jump Screen-
ing Test” in 205 female athletes (soccer, basketball, 
Table 1 Risk factors for knee and/or ACL injuries
Non-modifiable risk factors Modifiable risk factors
Age: < 20 years
Gender: female
Hormone status: preovulatory phase without contraception
Sports: soccer, handball, basketball, alpine skiing
Narrow intercondylar notch
Generalized ligamentous laxity
Pes pronatus valgus
Synthetic floor or turf
History of muscle, tendon, knee or ankle injuries
Infectious disease
Poor weather conditions (outdoor sports)
Dynamic valgus
Low flexion of hip and knee during landing
Poor hip and trunk control
Weakness of knee flexors and hip abductors (relative to knee extensors)
Delayed activation of flexors
Proprioceptive deficits
Muscle fatigue
Poor general fitness
 Arch Orthop Trauma Surg
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volleyball). This study verified a dynamic valgus position 
as one risk factor for sustaining an ACL tear. In female 
athletes with an ACL tear the knee abduction angle was 
increased by 8° when compared to healthy female controls. 
In this study, an abduction moment could predict an injury 
to the ACL with a specificity of 73% and sensitivity of 
78%. In the sagittal plane, the authors found a decreased 
maximum knee flexion angle of 10.5° during landing in 
athletes with ACL tear compared to healthy athletes (flex-
ion angle in athletes with ACL tear: 71.9° ± 12°; flexion 
angle in athletes without ACL tear: 82.4° ± 8°).
Another test for analyzing the dynamic valgus position 
is the “Single Leg Squat” (Fig. 2) [16]. In the original 
version of the test the athlete is positioned on a 20-cm 
box with folded arms: In this position the athlete should 
perform five single-leg squats with maximum flexion (one 
squat in 2 s). These squats are recorded by a video cam-
era. With different qualitative criteria the performance of 
the squats is graded in “good”, “middle” and “poor”. The 
criteria are listed in Table 2. Further, it is also possible to 
determine the frontal projection angle. Originally this test 
was designed to evaluate the dynamic valgus position in 
patients with patellofemoral pain syndrome. Ortiz et al. 
[48] also used “single leg squats” to assess the effect of a 
6 weeks’ ACL prevention program in female soccer play-
ers. The authors found a successful reduction of functional 
valgus during “single leg squats” after performing that 
Fig. 1 “Drop Jump Screening Test” to detect risk athletes. It con-
sists of a vertical jump from a box, in which the landing position 
is analyzed with a camera. The frontal projection angle or the dis-
tances between both knees and ankles could be measured (knee dis-
tance < ankle distance = dynamic valgus). During such landing situa-
tions the knee sustains the most uncontrolled movement
Fig. 2 Another test for analyzing the dynamic valgus position is the 
“Single Leg Squat” [16]. Therefore, the athlete should perform five 
single-leg squats with maximum flexion (one squat in 2  s). These 
squats are recorded by a video camera and graded as “good”, “mid-
dle” and “poor”
Table 2 Clinical assessment of single-leg squat according Crossley 
et al. [16]
To be classified as “good” in the overall assessment, 4 of 5 criteria 
have to be fulfilled. Athletes, who fulfill only one criterion, are clas-
sified as “poor”
CriterionTo be rated “Good”
(A) Overall impression
 1. Ability to maintain balance 5. No loss of balance
 2. Perturbations of the person 6. Smooth performance
 3. Depth of the squat 7. Squat with at least 60° of knee 
flexion
 4. Speed of the squat 8. 1 Squat per 2 seconds
(B) Trunk posture
 9. Lateral deviation 13. No lateral deviation
 10. Rotation 14. No rotation
 11. Lateral flexion 15. No lateral flexion
 12. Forward flexion 16. No forward flexion
(C) Pelvic posture
 17. Shunt or lateral deviation 20. No shunt or lateral deviation
 18. Rotation 21. No rotation
 19. Tilt 22. No tilt
(D) Hip
 23. Adduction 25. No adduction
 24. Internal rotation 26. No internal rotation
(E) Knee
 27. Valgus 29. No valgus
 28. Knee to foot position 30. Center of knee over center 
of foot
Arch Orthop Trauma Surg 
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prevention program. In these tests a valgus position of the 
knee was correlated with a reduced hip abduction [1, 16].
The “Functional Movement Screen” (FMS) is another 
test known in sports science to evaluate the risk of injury 
[10, 13, 42, 58]. The aim of the FMS is to detect functional 
asymmetries and disbalances [58]. The athletes have to 
complete seven different exercises, which are scored with a 
maximum of three points (three points: perfect performance, 
two points: evasive movements, one point: exercise is not 
possible, no point: pain). 14 points and more are associated 
with an increased risk of injury. Until now this test has been 
used only rarely for knee injury prevention since the main 
aim of the test is limited to injury risk assessment [10, 42]. 
A systematic review demonstrated a specificity of 86% for 
the FSM, but also a low sensitivity of 25% [18]. The predic-
tive value for risk assessment is also low [18]. Therefore, at 
the moment FSM is not recommended for ACL injury risk 
assessment.
Prevention program
Education about mechanism of injury and modification 
of endangering movement patterns
Concluding from the data regarding the genesis of an ACL 
tear, education about mechanism of injury could be part of 
prevention. Various studies are supporting this hypothesis.
Lephardt et  al. [38] using three-dimensional motion 
analysis demonstrated that endangering movement patterns 
could be modified with appropriate training. According to 
Cowling et al. [15], verbal instructions are already suffi-
cient to increase the knee flexion angle significantly during 
landing.
The approach for prevention of knee injuries was first 
described in the “Henning program”, a prevention program 
for ACL tears in basketball player [22]. The aim of this pro-
gram was to modify movement patterns to avoid endanger-
ing joint positions. The so-called “plant and cut” maneu-
ver should be performed smoothly in single small steps to 
avoid abrupt motions. During landing, after a jump the knee 
should be flexed and stopping should also be performed in 
several small steps and with avoidance of low knee flexion 
angles. This prevention strategy was educated to the sports-
men by means of a video film. With this approach of preven-
tion the injury rate was reduced by 89% [23].
Moreover, a study from alpine skiing demonstrated a pre-
ventive effect by education regarding injury mechanisms. 
Within the “Vermont ACL prevention program” athletes 
were confronted with videos of typical ACL injury situations 
during skiing. These videos should stimulate the athletes 
to develop individual prevention strategies [20]. Further-
more, the videos should help to detect endangering situa-
tions and to develop strategies as a response to the injury 
stimulus in “almost injury” situations. In the winter season 
of 1993/94 4700 ski instructors and ski slope patrols took 
part in this program. Hereby the rate of severe knee injuries 
was reduced by 62% [20].
In summary, there are certain indications that education 
about injury mechanism and modification of endangering 
knee movement patterns could avoid ACL tears (Table 3).
The avoidance of dynamic valgus position and landing 
with flexed knee are the basis for exercises and warm-up 
programs with the aim to prevent knee and ankle injuries.
Balance training
Proprioception (afferent information on joint position) rep-
resents the sensorial source of information that enables neu-
romuscular control of the joint [37]. Proprioceptive informa-
tion is given by different mechanoreceptors that are located 
in muscles, joints (ligaments and capsule), and the skin. 
In the knee joint this mechanism regulates the interaction 
between the extensor and flexor muscles, which is crucial 
for balancing the stress on the ACL but can be practiced by 
balance training (Fig. 3).
It has been shown that exercises on a balance board 
decrease the incidence of primary and secondary ankle joint 
injuries [7, 64, 66]. However, current literature is lacking 
consistent data regarding the benefits of such exercises on 
Table 3 Avoidance of 
endangering movements Frontal plane Sagittal plane
Avoidance of dynamic valgus
 Centers of hip, knee, and ankle are aligned During landing after jumping the hip and the knee 
should be flexed (if possible 90°) and should not be 
straight
 Knee pointing externally Body’s center of gravity over the foot
 Hips are horizontal
 Trunk is upright
Rotation as a smooth movement in single steps
Stopping with several small steps and without extended knees
 Arch Orthop Trauma Surg
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the incidence of ACL injuries. Caraffa et al. [11] conducted 
a study with 300 male soccer players and found a significant 
reduction of ACL injuries due to exercises on the balance 
board [10 ACL injuries in the study group (n = 300) versus 
70 ACL tears in the control group (n = 300)].
Wedderkopp et al. [67] analyzed an intervention program 
including exercises on balance boards as well as muscle 
strengthening on juvenile female handball players. In this 
study a decrease of the injury rate by 78% was shown by 
applying this prevention program. In order to investigate the 
preventive effect of balance training, another study com-
pared two different prevention programs on 16 female hand-
ball teams: (1) Standardized strengthening exercises (control 
group) versus (2) Combination of strengthening exercises 
and balance board training (study group) [68]. It was found 
that the incidence of injuries was reduced from 6.9 per 1000 
playing hours in the control group to 2.4 injuries per 1000 
playing hours in the study group. However, on the basis of 
the given data a statement regarding knee injuries was not 
possible.
Contrary results were reported by Soderman et al., who 
conducted a balance board training with 121 juvenile female 
soccer players [59], while further 100 players served as con-
trol group. After one season of observation there was no 
significant difference between both groups regarding fre-
quency of injuries. The incidence of severe injuries was even 
higher in the intervention group (8 versus 1) with four out of 
five ACL ruptures in this group. Only in patients, who have 
had injuries within the past 3 months prior to the beginning 
of the study, a significant lower injury rate was observed in 
the intervention group.
In summary, on the basis of current data, the usage of 
balance boards should be recommended as the general inci-
dence of injuries can hereby be reduced. In several studies, 
which demonstrate a positive effect of preventive warm up 
programs, balance training is included in these programs 
[41, 46, 49, 50, 54]. Especially the combination of balance 
exercises with sport-specific exercises is an appropriate sup-
plement to warm up programs (Fig. 4).
Neuromuscular training
Athletes at high risk for ACL injuries are characterized by 
a dominance of the quadriceps muscle, as on an experimen-
tal anterior tibial translation (injury stimulus)these athletes 
react with quadriceps activation. By contrast, several studies 
have demonstrated that a rapid activation of the hamstring 
muscles as a reaction on an injury stimulus helps to protect 
the knee joint [5, 8, 26, 33, 60].
Fig. 3 Proprioception exercises on a balance board; leg position has 
to be noted and a dynamic valgus position has to be avoided
Fig. 4 Combination of balance exercises with sport-specific exer-
cises
Arch Orthop Trauma Surg 
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Hewett et al. [27] could show that by means of a specific 
jump training, activation of the hamstring and gluteal mus-
cles can be increased and, therefore, also a possible imbal-
ance between the quadriceps and the hamstring muscles can 
be reduced. In this context, it is important that during land-
ing, both the athletes knees and hips are flexed by 90°. On 
the basis of this knowledge the “Cincinnati Sportsmetric 
Training Program” has been introduced. This prevention 
program has been tested on 1263 athletes (football, volley-
ball, basketball) [28]. It consists of different jumping exer-
cises with increasing complexity. In this regard, too, move-
ment control based on the principles proposed by Henning 
[23] is very important in order to avoid endangering move-
ment patterns. In the study by Hewett et al. only two athletes 
of the training group suffered severe injuries compared to 
ten athletes of the control group. The relative incidence for 
injuries was 0.12 in the training group and 0.43 in the con-
trol group. Summarized, the studies by Hewett et al. [27, 
28] show that specific jumping exercises can improve the 
balance between flexor and extensor muscles at the knee 
joint; however, consideration of Henning’s principles for 
movement modifications is crucial [23].
Therefore, jumping exercises have been included in sev-
eral warm up programs [41, 46, 49, 50, 54] and are par-
ticularly suited for sport disciplines with repetitive jumping 
tasks.
Strength training
Because of the crucial role of muscle imbalance in the 
occurrence of dynamic valgus alignment and the associated 
risk of ACL tears, strength exercises have been integrated in 
many prevention programs [17]. These are primarily focus-
ing on the knee flexors, hip abductors, and trunk stabilizers 
[29].
Muscle strength training can be performed using basic 
training devices at the gym. However, for a better integration 
of muscle strength training into warm up programs, dynamic 
exercises have been developed that can be performed by 
means of simple training tools [29].
Typical strength exercises for ACL prevention are the 
“Russian hamstrings” [29], which activate the posterior 
muscle chain both concentrically (upwards) and eccentri-
cally (downwards) (Fig. 5).
The flexor training on the exercise ball represents a fur-
ther possibility to strengthen the posterior thigh muscles as 
well as the abdominal muscles and the stabilizers of the hip. 
In addition to that, exercises that strengthen the hip abduc-
tors and the hip rotators are included in ACL prevention 
programs (Fig. 6) [29].
Several studies that could show a positive effect of pre-
ventive warm up programs include strength exercises in 
their warm up programs [21, 35, 41]. Individual strength 
exercises, however, have not been tested separately so far.
Running und flexibility training
Running exercises are suitable for injury prevention as they 
are a classical part of every warm up program.
Running and flexibility exercises have been integrated 
into the “Prevent Injury and Enhance Performance Program” 
(PEP), which was developed especially for the prevention 
of ACL injuries in football [21, 41]. It includes different 
Fig. 5 Muscle strength training: typical exercises for ACL prevention 
are the “Russian hamstrings”, which activate the posterior muscle 
chain both concentrically (upwards) and eccentrically (downwards)
Fig. 6 Flexor training on the exercise ball represents a possibility to 
strengthen the posterior thigh muscles as well as the abdominal mus-
cles and the stabilizers of the hip
 Arch Orthop Trauma Surg
1 3
running exercises (e.g., straight ahead running, side steps, 
running with hip rotation). It is important that the instructors 
pay special attention to the correct execution of these exer-
cises. Above all, a dynamic valgus has to be avoided. Several 
studies have shown that the PEP can significantly decrease 
the prevalence of ACL injuries in football players [21, 41]. 
However, there are no studies, which have investigated the 
effect of individual running exercises separately.
The effect of specific warm up programs 
on the prevention of ACL ruptures and knee injuries
Several systematic reviews and meta-analyses have shown 
that the risk of knee injuries and ACL ruptures can be sig-
nificantly reduced by specific warm up programs [17, 24, 
31, 61, 62, 69].
In a meta-analysis of 24 studies, published in 2015, a 
preventive warm up program could reduce knee injuries 
by 26.9% and ACL ruptures by 50.7% [17]. Nine of these 
studies reported additional prevention of musculoskeletal 
injuries in general. Although the majority of these studies 
focused on female athletes, a preventive effect could also 
be demonstrated for male athletes [17]. Most studies have 
investigated programs that have combined multiple preven-
tive concepts: balance training, jumping exercises, strength 
exercises, running, flexibility exercises, and stretching [17]. 
However, a meta-regression analysis did not show a signifi-
cant effect on the results by any of these individual proce-
dures [17]. Only for stretching a little evidence could be 
shown that it has no effect on the result [25, 65]. Probably 
the effect of the different preventive procedures is based on 
modifications of dangerous movement patterns (dynamic 
valgus, low knee and hip flexion). Therefore, the individual 
preventive exercises, which are presented in this article, can 
be combined in such a way that the warm up programs are 
suitable for the specific sports discipline. Hence, running 
exercises are suitable for football, jumping exercises for 
handball or basketball, and strength exercises for skiing. It 
seems reasonable that these exercises are combined with 
sport-specific exercises as this can increase the compliance. 
Furthermore, it could be demonstrated that movements of 
the upper extremities can influence movement patterns of 
the lower extremities [14].
There is also evidence that the timing of preventive pro-
grams has an influence on the efficacy of risk reduction. Per-
forming the preventive training during the pre-season period 
shows a significantly higher effect than performing it only 
during the competitive period [17]. Further effects on the 
efficacy of preventive programs could be shown for duration, 
frequency, and compliance. The longer the duration of the 
program (> 20 min) and the more frequent it is conducted 
(> three times per week), the greater is the effect [61, 62].
Established prevention programs
Table 4 gives a summary of different established warm up 
programs for prevention of knee injuries and ACL ruptures. 
The preventive effect on primary ACL injuries is scien-
tifically proven for most of these programs; however, their 
effects on the secondary prevention of a re-rupture after 
ACL reconstruction are still to be investigated.
All of these programs are available via Internet. They 
have been developed specifically for ball sports (football, 
handball, basketball) and include balance, strength, jumping, 
Table 4 Overview of established warm up programs for injury prevention
R running exercises, P plyometrics (jumping exercises), S strengthening exercises, B balance training, F flexibility training/stretching
Name Discipline Exercises Duration (approx.) Scientific evidence Web addressFIFA 11+ Football R, P, S, B 20 min Soligard et al. [61] www.dfb.de/trainer/b-juniorin/
artikel/fifa-11-310/
www.fmarc.com/downloads/
cards/11pluscards_d.pdf
www.f-marc.com/1lplus/
startseite/
Prevent injury and enhance 
performance (PEP)
Football R, P, S, F 20 min Mandelbaui et al. [41] smsmf.org/files/PEP_
program_0412201l.pdf
Sportsmetrics Football, basketball, 
tennis, volleyball
P, S 60 min Hewett et al. [27, 28] http://sportsmetrics.org/
Harmo Knee Prevention 
Program
Football, basketball R, P, B, F 20–25 min Kiani et al. [35] harmoknee.com
“Sei kein Dummy” (prevention 
program of VBG)
Football R, P, S, F 20–30 min – http://www.vbg.de/Shared-
Docs/Medien-Center/DE/
Broschuere/Branchen/Sport/
Trainingsuebungen_fuer_
ein_starkes_FuBballteam.
pdf?_b
Arch Orthop Trauma Surg 
1 3
running, and flexibility exercises. The aim of these exercises 
is to reduce the dynamic valgus and to strengthen the poste-
rior muscle chain (flexor muscles of the knee and abductor 
muscles of the hip). These exercises can be modified and 
integrated into specific warm up programs of other sports 
disciplines of high risk (e.g. judo, hockey, skiing). This inte-
gration is very useful in order to increase the athletes’ com-
pliance. The duration of most of the warm up programs is 
20 min. The application of preventive procedures is intensi-
fied during the pre-season period, while it is reduced during 
the competition period.
Conclusion and recommendations
Especially in non-contact situations there are typical move-
ment patterns with increased risk of ACL injuries in ath-
letes. Dynamic knee valgus with only slight flexion in the 
knee and hip joints after landing or during sudden direction 
change seems to be particularly predisposing. In this respect, 
several “screening” tests like single-leg squats or jumping 
tests have been developed, that can help to detect athletes 
at risk.
There is significant evidence that the incidence of knee 
injuries and ACL ruptures can be reduced by appropriate 
modifications of the athletes’ training. In this regard preven-
tion programs should be based on the following aspects:
1. Information about injury mechanisms,
2. jumping exercises for muscle strengthening and correc-
tion of movement patterns,
3. balance training,
4. strength training,
5. running/flexibility exercises.
These preventive exercises should be integrated into the 
usual warm up program in combination with sport-specific 
exercises. Thus the athlete’s motivation and compliance can 
be kept high and no further resources are needed. Corre-
spondingly several complete warm up programs have already 
been developed, which are freely accessible via the Internet.
However, to date the effectiveness of these programs is 
only evident for ball sports, while their influence in other 
sports with higher rates of contact injuries like Judo has not 
been investigated so far. So, further research is needed in 
this field. Nevertheless, until further data are available we 
recommend the same exercises adjusted to the specific warm 
up programs also for these sports.
Acknowledgements The ligament committee of the German Knee 
Society (DKG) developed this study to provide guidelines regarding 
the topic prevention of knee and ACL injuries. Members are listed 
below. Petersen W, Zantop T, Imhoff A, Müller P, Patt T, Scheffler S, 
Höher J, Stöhr A, Ellermann A, Stoffels T, Jung T, Herbort M, Akoto 
R, Achtnich A, Diermeier T, Mehl J, Herbst E, Stein T.
Compliance with ethical standards 
Conflict of interest The authors declare that they have no conflict 
of interest.
Funding There is no funding source.
Ethical approval This article does not contain any studies with 
human participants or animals performed by any of the authors.
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	Evidence-based concepts for prevention of knee and ACL injuries. 2017 guidelines of the ligament committee of the German Knee Society (DKG)
	Abstract 
	Introduction 
	Methods 
	Results 
	Conclusions 
	Introduction
	Methods for guideline development
	Injury mechanisms and assessment of risk factors
	Injury mechanism
	Athletes at risk
	Screening tests
	Prevention program
	Education about mechanism of injury and modification of endangering movement patterns
	Balance training
	Neuromuscular training
	Strength training
	Running und flexibility training
	The effect of specific warm up programs on the prevention of ACL ruptures and knee injuries
	Established prevention programs
	Conclusion and recommendations
	Acknowledgements 
	References