Groin injury in soccer
Steps towards a sport-specific approach. From hypothesis to physical examination and treatment
– Written by Igor Tak and Rob Langhout, The Netherlands
Groin injuries account for 10 to 15% of all soccer related injuries. A small number of these become chronic and in some cases groin injury is career-ending. As imaging findings are not well-correlated with complaints, Hölmich introduced a clinical classification system. This describes entities such as adductor-related and iliopsoas-related groin pain. These entities can occur in isolation or combined. Adductor-related groin pain is the most frequent entity in soccer players and often affects the kicking leg. In our practice more than 90% of injured players reported not being able to kick a ball with maximal power. Players switch to submaximal instep kicking to avoid the pain, allowing them to continue playing until pain levels increase and they eventually have to stop training or matches. In cases of long-standing adductor-related groin pain (LARGP) conservative treatment is often recommended. Exercise therapy is widely used and this treatment is supported by a few high quality studies.
Range of motion (ROM) as a risk factor for groin pain has been studied. The conclusions are conflicting and the role of ROM in soccer and groin pain remains unclear. There are no studies on its role in treatment. The aim of this article is to discuss ROM as a risk factor in groin pain, the importance of sport-specific ROM in soccer, present a new way of testing and measuring sport-specific ROM and our findings in healthy and injured players. This is used to propose a stepwise approach in treatment.
RANGE OF MOTION AS A RISK FACTOR
Range of motion issues of the hip have been addressed in several studies on groin pain. ROM measurements are reliable for the hip joint. Some studies showed that decreased hip ROM is a risk factor for groin pain in sports while other studies failed to find a relationship. Studies examining adductor flexibility display the same inconsistent pattern. The majority of these found no relationship. We conclude that evidence for decreased hip joint ROM or adductor muscle flexibility being a risk factor is weak and that the findings are contradictory.
LIMITATIONS OF CLASSICAL ROM TESTING
Considering the methods of testing hip and adductor flexibility its is our opinion that body positions do not correlate well enough to functions needed by the athlete. Some authors who failed to find a relationship earlier made comments that classical ROM testing is one or two-dimensional and therefore lack the 3D characteristics of sport-specific movements. They suggested a more functional assessment, involving core and leg function.
These widely-used and generally accepted classical tests do not measure ROM according to recent insights into the biomechanical importance of the upper body during kicking.
SPORT-SPECIFIC ROM DEMANDS IN SOCCER
In clinical practice we observed that even a slight loss of hip ROM on the injured side became more pronounced when the player was placed in the kicking position, recreating the backswing position. The backswing resembles the functional range of motion that the body uses to store potential energy before transferring it into kinetic energy to kick the ball. Biomechanical studies demonstrate that the backswing of the instep kick does not only consist of local hip extension but also uses considerable upper body rotation combined with hip rotations and abduction and adduction. This leads to foot velocity derived from moments (motion dependent moments) and not velocity as a result of muscle action. The advantage of motion dependant moments is their safety and this will be discussed in more detail later. In an on-going current study we found that a larger range of full body backswing correlates to high ball velocity (non-published data). In cases of decreased backswing flexibility, the player must switch to another kicking strategy. Increased muscle contraction of hip and knee muscles will be needed to compensate for the decreased motion-dependent moment, thereby potentially placing these muscles at risk.
From this perspective, hip ROM should not only be examined in an extended position but should also be related to a rotated upper body position.
SPORT-SPECIFIC ROM AND BETTER OUTCOME OF TREATMENT
A reliable measurement of sport-specific ROM, representing the full body tension arc, might help to investigate the relationship between ROM and adductor-related groin pain. This may provide a more clinically relevant assessment than local hip examination does. We developed a way to further test this idea taking into account that:
· Energy transfer (potential to kinetic) in the body occurs around total body extension, enabling the body to kick effectively and safely.
· Players with groin injury demonstrate less powerful kicking.
· We found that loss of ROM became more pronounced in a sport-specific posture.
This seemed legitimate as other injury-specific movement restrictions in relation to sport, such as glenohumeral internal rotation deficit and posterior capsule tightness in the throwing shoulder, are now generally recognised as risk factors and modifiable variables. Therefore we propose using a comparable concept of ROM like that used in throwing athletes with shoulder pain. The throwing motion resembles the same goal:
‘to create the highest possible level of potential energy in the body and transfer it to kinetic energy.’
The hip and shoulder show much similarity concerning position and function in relation to the trunk. The shoulder and hip are the dynamic links between trunk and limb and for both, trunk flexibility plays a role in ROM capacity of the adjacent limb in 3D space. Even hip rotation is important in throwing actions for developing speed throughout the kinetic chain. A greater range of motion of the arm in 3D space allows less stress on anatomical tissues and lower muscular contraction levels because speed can be created over a larger trajectory resulting in larger motion-dependent moments. In order to come up with a model for this approach for the lower limb, the literature on biomechanics in soccer was used.
INSTEP KICKING IN SOCCER
The soccer kick can be roughly divided into a back swing and down swing phase. Brophy proposed that the kick be divided into five different phases (Table 1). The body positions that occur during these phases are shown in Figures 1 to 5.
Backswing and range of motion
The most important findings are the creation of a whole body tension arc, like drawing back a bow, which works to store energy. Later, in the acceleration phase, speed towards the ball is developed and the highest foot speed occurs at ball impact. The body segment positions in the consecutive phases of energy storage (tension arc) up to their maximum (back swing and leg cocking) are displayed in Table 2 and 3.
After examining the motion we developed a full body ROM test with the body positioned to mimic the position of leg cocking, with 90° knee flexion. The upper body was positioned in extension and ipsilateral rotation with the contralateral (non-kicking side) arm in horizontal abduction (Figure 6a). In this position multi-segmental hip extension can be measured. For other directions the athlete is positioned laying on their side and adduction, abduction and internal and external rotation are measured (Figure 6 b-e). When added together these directions represent the ‘biological workspace’ of the backswing. Reliability testing of this method of measuring ROM reveals moderate to excellent values (non published data).
Testing two cohorts of healthy players revealed that there was no significant asymmetry between legs. This is the case for amateurs as well as professional elite players. Testing was performed in different levels as higher playing levels have been associated with decreased hip ROM in classical testing. When positioning our patients with LARGP in this position we noticed significantly decreased ROM (around 30%) in all directions between the injured and non-injured leg (non published data). We think that this means that the ‘biological workspace’ for the lower limb is reduced in this football-specific posture. During kicking energy has to be stored in a smaller ROM trajectory, increasing stress levels on the structures involved.
FROM CONCEPT OF INJURY TO CONCEPT OF TREATMENT
Active strength training has shown to be effective in the treatment of LARGP. From a ROM perspective, multi-directional restriction, measured in a sport-specific manner, in players with LARGP has never been described before. We propose this restriction, which we call ‘Hip Extension Rotation Ab- and Adduction Deficit’ (HERAD), to be a clinically relevant finding.
It shows the decreased ability of the body to efficiently create and use a large motion-dependent moment for kicking. Muscular compensations may occur as a result and precede tissue damage and delay recovery.
In clinical practice we have found HERAD to be reversible in athletes with LARGP. We base the treatment strategy and the choice of techniques on the restricted structures and on the underlying pathophysiological mechanism. The sports-specific test battery, while capable of demonstrating unilateral lower limb stiffness (HERAD) in athletes with LARGP, cannot identify where the restriction is located. Therefore, after detecting full body asymmetry, the ROM of all structures in the kinetic chain should be examined as well (Table 4). We propose to use a stepwise approach with respect to treating ROM issues in order to create improved conditions for strength training and load-bearing:
1. The treatment of the adductor longus muscle. This aims at a normal ‘glide’ of its fascia with the adjacent muscles (adductor brevis, magnus and gracilis) and of the intramuscular fascia of the adductor longus itself. Transverse mobilisations and stretch techniques can be used in combination with adductor manipulation (Figure 7). In a current study on the effect of adductor longus manipulation it seems to contribute to increased load-bearing capacity of patients suffering LARGP, as reflected by improvement on scores on pain, all Copenhagen Hip and Groin Outcome Score (HAGOS) scales and short-term return to play (non-published data). After adductor longus manipulation we observe that the sport-specific ROM improves immediately. Manipulation may therefore be a valuable add-on in treatment programmes.
2. In order to reduce muscle tension (tone) in a segmental, neuroflector approach, interventions are manually applied to ‘key joints’ such as the hip and thoracolumbar spinal joints. We prefer the use of manual therapeutic High-Velocity Low-Amplitude techniques (HVA) because of the direct inhibition on muscle tension.
3. Then we aim at regaining a symmetrical full body ROM of the tension arc. We start with local treatment of the restricted joints and muscles. In doing so, the axis of rotation will be repositioned in their physiological positions. This prevents compensatory movements of adjacent joints to occur during full body stretching. Mobilising restricted joints and muscles that participate in the formation of the tension arc can be done with common techniques. Then, stretching the myofascial lines needed for the tension arc can be performed in the testing position by the therapist, but also using exercises for the athlete (Figure 8).
In practice we have found between one to three treatment sessions are sufficient to regain full body sport-specific ROM. We observed that after this treatment the resisted adduction provocation test is less painful or painless. At this point the athlete improves their load-bearing capacity (see Step 1). This situation is ideal for active training and rehab regimens with the primary goal to improve the strength of the adductor longus and restore adductor/abductor balance. We hypothesise that restoring balance and symmetry to the sport-specific ROM before the onset of active strength training will improve the clinical outcome.
After the strength has been restored, performance of football actions should take place with gradual increased loading progressing through sprinting, cutting, pivoting and kicking. Unfortunately, measuring qualitative aspects of such high velocity actions is only possibly with expensive high-tech motion capture systems. Preliminary data from our current 3D motion capture study confirm that maximal hip extension in the backswing is accompanied with a horizontal orientated shank and with maximal horizontal extension of the non-kicking arm in order to accelerate hip flexion. This key point may provide information on kicking strategies whether the football player kicks the ball with a high level of flexibility or by using other strategies such as muscle power.
We suggest that further studies should target these ideas to search for key points that can help identify a low risk, high performance kick. New studies should also focus on the hypothetical added efficacy of restoring sports-specific ROM in the rehabilitation of groin injury. Insight into the normal co-ordination patterns of all body segments during the downswing, consisting of the phases of leg cocking and acceleration is needed. Only then can the effects of groin pain on co-ordination can be established.
When measured in a traditional non-specific way there is conflicting evidence on the role of hip ROM and adductor flexibility as a risk factor for groin pain. We propose a sports-specific test battery for football players. Initial data suggest the battery is reliable and that in healthy player there is no significant asymmetry.
Our observations in athletes with long-standing adductor-related groin pain suggest that they have a reduced sports-specific ROM. We propose a treatment regimen to restore ROM before the onset of further rehabilitation, and hypothesise that this will improve the clinical outcome.
Figure 7: https://www.youtube.com/watch?v=fFnHSxM8U2A
Figure 8: https://www.youtube.com/watch?v=uqIyDkfr45Q
Igor Tak M.Sc., P.T., M.P.T.S.
Director and consulting physical therapist in sports
Fysiotherapie Utrecht Oost
Utrecht, The Netherlands
Rob Langhout P.T., M.M.T.
Director and consulting manual therapist
Nijmegen, The Netherlands
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Image via Micaela Ayala