Case Study: ACL Injury in Football

The risk of injury in professional football is almost 1000 times greater than other professions (McCall, Carling & Berthoin et al, 2014) with injury incidence having a strong correlation with a team’s final league position (Eirale, Tol & Farooq et al, 2013). Evidence based injury prevention strategies have been shown to decrease the risk of injuries among football players (Attar, Soomro, Pappas & Sanders, 2015) therefore, increasing player availability for team selection. By identifying risk factors, choosing appropriate performance tests and implementing science based injury prevention programs, the sport scientist may assist in preventing the occurrence of injuries that can be detrimental to successful team performance.

This case study is presented on one player at Ebbsfleet United Football Club, who suffered an anterior cruciate ligament injury during a competitive match in September 2016. Anterior cruciate ligament injuries can result in lengthy lay-offs and even be career threatening for many professional athletes (Busfield, Kharrazi & Starkey et al., 2009). Therefore, the purpose of this case study is to investigate the cause and effect of this injury and explore the recovery process and prevention strategies involved in a successful return to play and re-injury avoidance.

Player Background and Pre-Injury Benchmarks

The player presented in this case study is 33 years of age and currently plays in the fifth tier of English football. He made his professional debut in 1999 and has made over 300 appearances in the English Football League (including the Premier Division). The player’s information and pre-season physical performance test data are displayed appendix A. His peak power value from a counter movement jump was 16.4% higher than team average and 9.3% higher than his position average of striker. There was a 6.02% difference in right and left leg power output during a single leg counter movement jump; with the left (standing leg) measuring 4794W and right (kicking leg) measuring 4522W respectively. This player was also 1.3% and 1.0% faster than the team average and 1.0% slower and 0.6% faster than his position average in 10m and 30m sprint tests.

After completing a pre-season testing battery in the final week of 06/2016, pre-season training commenced on the 05/07/2016 with a seven-day training camp in Portugal. On return from Portugal and throughout the season, training was reduced to three days a week with one match at the weekend. The competitive season began on 06/08/2016. The players first appearance of the season came on 27/08/2016. The injury occurred five matches later (13/09/2016) in the 70th minute, after 460 minutes of exposure to competitive match play and 44.9% of total season match minutes played.

Anterior Cruciate Ligament

The anterior cruciate ligament (ACL) is one of four primary ligaments of the knee that act to provide significant stability by acting as restraints to translation and rotation (Parvizi, 2011). It arises from the posterior aspect of the medial surface of the lateral femoral condyle, and runs anteriorly, medially, and distally to insert into the anterior tibial spine. It is considered stronger at the tibial attachment point due to the fibres fanning out as they proceed distally (Ellenbecker, 2011) and provides 86% of the resistance to anterior displacement and 30% to medial displacement (Norris, 1997). The ACL consists of two ligamentous tissue bands, the anteromedial and posterolateral bundles. The main function of the larger anteromedial bundle is to resist anterior translation of the tibia on the femur, whereas the posterolateral bundle resists abnormal anterior lateral rotation of the tibia on the femur.

As the knee moves back and forth through flexion and extension, there is an increase in the tightening and loosening of these fibres. The posterolateral part of the ACL is taut in extension and the anteromedial portion is lax. In flexion, all the fibres except the anteromedial portion are lax (Norris, 1997).

Physiology of Football

During a 90-minute football match players can be expected to cover total distances of between 10-12km (Mohr, 2003). Sprinting constitutes 1-11% of the total distance covered (Rienzi, 2000), with numerous other explosive activities required such as tackling, jumping, turning, acceleration/deceleration, change of direction and sustaining forceful contractions to maintain balance and control of the ball while under defensive pressure (Stolen, 2005). Hawkins et al., (2001) reported that there was an average of 1.3 injuries per player per season in English professional football. They also found that the greatest injury rate occurred in the final 15 minute periods at the end of each half, with significantly more injuries in the second half.

Injury Aetiology

The two most commonly described ACL injury situations in sport are turning of the trunk when the foot is fixed to the ground (rotation and abduction), or landing awkwardly from a jump (Faunø and Jakobsen, 2006) although in contrast to this, the injury experienced by the participant presented in this case study occurred from a direct impact injury (fig. 1). ACL injuries are relatively uncommon in football compared to other soft tissue injuries such as thigh muscle strains or ankle sprains (Árnason et al., 2004) with elite teams experiencing approximately 0.4 ACL injuries per season (Walden, 2011). Match play is associated with a much higher risk of injury than training (Walden, 2011).

As the player approached the opposing defender to close-down a clearance, he slid on the floor with an extended leg to block the ball. It then appears that the defender has cleared the ball, with the ball or defenders leg then contacting the participants’ lower leg. The force of this anterolateral impact has led to valgus and in addition to hyperextension has resulted in injury to the knee, thus causing a rupture of the ACL.

Walden et al (2015) found that 85% of all ACL injuries in professional football were as a result of a non-contact or indirect contact mechanism, further reiterating the uniqueness of the present injury. The number one situation in football was described as pressing, which was categorized as a trunk rotation coupled with a planted foot. The second most common situation was regaining balance after kicking and then finally landing after heading.

ACL Injury Pathology

ACL Injury occurs in situations when there is an over stretching or tearing of the ligament. A tear may be partial or complete, although partial tears of the anterior cruciate ligament are rare. Therefore, mot ACL injuries are complete or near complete tears. The combination of rotation and abduction of the knee most frequently seen in ACL injury is a similar action to that which causes medial collateral ligament (MCL) and medial meniscus damage, inferring that these structures are very often also effected during an ACL injury. When all three structures are effected as a result of injury they combine to form what is known as an ‘unhappy triad.’

Injured ligaments are considered sprains and are categorized by severity using a grading system as described below.

Grade 1

[if !supportLists]· [endif]Mildly damaged

[if !supportLists]· [endif]Slight stretched, but still able to help stabilize the knee joint

Grade 2

[if !supportLists]· [endif]Becomes loose

[if !supportLists]· [endif]Referred to as a partial tear of the ligament

[if !supportLists]· [endif]Rarely occur

Grade 3

[if !supportLists]· [endif]Most commonly referred to as a complete tear

[if !supportLists]· [endif]The ligament has been split into two pieces, resulting in joint un-stability

[if !supportLists]· [endif]Most common diagnosis

Treatment and Rehabilitation

Factors that may influence the appropriate treatment of an ACL injury include age of the patient, level of activity, severity of the tear and the ability of the patient to comply with the rehabilitation program. The repair process normally involves either an operative or non-operative procedure. An acute injury to the ACL without other major ligamentous damage can be treated with non-steroidal anti-inflammatory drugs and physiotherapy to reduce inflammation and restore full range of motion (Johnson, Beynnon, Nichols and Renstrom, 2010).

The player presented in this study received a full ACL reconstruction operation. An MRI scan revealed that there was a detachment of the ACL from the femoral insertion. It also revealed that there was a slight sprain seen in the lateral collateral ligament, but no damage to menisci. During the surgical procedure it was discovered that there was a rupture of the posterolateral bundle, therefore the surgeon elected to reconstruct the ligament. A graft was taken from the patella tendon to replace the previous ruptured ligament. Post operation the participant was advised to commence full weight bearing using crutches for the following three weeks with an emphasis on full active extension as soon as possible. An MRI and surgical procedure report can be found in appendix B.

As the player was a member of the Professional Footballers Association this allowed access to state of the art treatment at St. Georges Park, which is where a lot of the rehabilitation took place.

Phase 1 (Week 1-3)

Following surgery, it is important to correct any abnormalities in gait. The initial phase of the rehabilitation process consisted of gait training and regaining functional control of the quadriceps. This was accomplished by walking on an anti-gravity treadmill starting at 45% body weight for 5 minutes 2-3 times per week, progressing to 65% bodyweight for 15 minutes 3-5 times per week by the end of week three. If an anti-gravity treadmill is not accessible, this phase may be completed using swimming pool or stationary cycle to unload body weight. Close kinetic chain exercises that promote a coactivation of the muscles spanning the knee have been shown reduce the amount of strain placed on the ACL compared to isolated knee extension exercises. Close kinetic chain exercises in this phase consisted of [if gte msEquation 12]><m:oMath><m:f><m:fPr><m:ctrlPr></m:ctrlPr></m:fPr><m:num><m:r><m:rPr><m:scr m:val="roman"></m:scr><m:sty m:val="p"></m:sty></m:rPr>1</m:r></m:num><m:den><m:r>3</m:r></m:den></m:f></m:oMath><![endif][if !msEquation][if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:stroke joinstyle="miter"></v:stroke> <v:formulas> <v:f eqn="if lineDrawn pixelLineWidth 0"></v:f> <v:f eqn="sum @0 1 0"></v:f> <v:f eqn="sum 0 0 @1"></v:f> <v:f eqn="prod @2 1 2"></v:f> <v:f eqn="prod @3 21600 pixelWidth"></v:f> <v:f eqn="prod @3 21600 pixelHeight"></v:f> <v:f eqn="sum @0 0 1"></v:f> <v:f eqn="prod @6 1 2"></v:f> <v:f eqn="prod @7 21600 pixelWidth"></v:f> <v:f eqn="sum @8 21600 0"></v:f> <v:f eqn="prod @7 21600 pixelHeight"></v:f> <v:f eqn="sum @10 21600 0"></v:f> </v:formulas> <v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"></v:path> <o:lock v:ext="edit" aspectratio="t"></o:lock> </v:shapetype><v:shape id="_x0000_i1025" type="#_x0000_t75" style='width:5.25pt; height:20.25pt'> <v:imagedata src="file:///C:/Users/Stuart/AppData/Local/Temp/msohtmlclip1/01/clip_image001.png" o:title="" chromakey="white"></v:imagedata> </v:shape><![endif][if !vml][endif][endif] knee bends in double foot stance. These exercises could be performed on the anti-gravity treadmill while the belt remains stationary. Icing was used to manage an inflammation still present.

Phase 2 (Week 3-6)

This phase of rehabilitation was focused on safely restoring full soft end feel flexion and firm extension to stop. Emphasis on improving single leg load tolerance with the end goal of this stage being able to perform 10 squats to 30º knee flexion, without pain. Other exercises included core and hip stability and strengthening of the calves. The volume generally consisted of 3-4 sets of 15-20 reps per exercise daily. Single leg squats were performed on an 8” step with the opposite heel descending to tap the floor. An emphasis was placed on biomechanics of these movements ensuring proper knee alignment and foot position throughout. Walking continued on the anti-gravity treadmill increasing the resistance from 65% body weight up to 80-90% body weight by the end of week 6, with incline also increasing from 3-5%.

Phase 3 (Week 6-12)

The main goal at this stage was to attempt to restore strength to normal, and full range of motion. An isokinetic dynometer was used to compare quad/hamstring strength ratio with injured and non-injured leg. Strength training was the primary focus here with volumes increasing to 6 sets of 8-12 reps on each exercise. Walking continued on the ant-gravity treadmill, increasing volume to 20-30 minute sessions 2-3 times per week. This progressed to running at 55% bodyweight by week 10 on a 0% incline for 5-10 minutes, performed twice per week.

Phase 4 (Week 12+)

Strength training increased from week 12 onwards, increasing single leg strength further through closed kinetic chain exercises such as squat and single leg squat. Ballistic exercises slowly began to be introduced such as stationary and forward hopping. Proprioception exercises also continued with single leg balance exercises on a Bosu ball. Strength testing was performed in week 16 to again establish left/right strength imbalances. There was a slight set back at this stage due to a muscle imbalance larger than what would be expected for this period of recovery. This was amended by week 16. There was still a moderate imbalance of power output in single leg counter movement jump, compared to pre-season testing (6% at pre-season, and 12% at week 16 of rehabilitation). Running continued in a straight line, and gradually progressed to multi-direction and acceleration/deceleration and more sport specific movements. An example 10 day program is in appendix C.

Return to Sport

ACL surgery is effective in allowing athletes to resume their sporting careers as most patients (65-88%) are able to return within the first year (Fellar and Webster, 2003). In a systematic review Walden et.al., (2011) found that 94% of ACL reconstructed players returned to training within 10 months after surgery, with 94% participating in a match within 12 months, post-surgery. This is obviously dependent on the severity of the initial injury and the players’ compliance with the rehabilitation process. In terms of severity of injury, the player presented in this case study may be considered on the lower end of the spectrum, based on damage to the knee being restricted to the ACL only and no other structures.

What is of significance is how long players can continue playing after the initial injury. Roos et al., (1996) found that only 30% of elite football players were active in sport three years post initial injury and after seven years there were no players competing. The reason for this being that many athletes that return to sport after this injury experience significant knee problems such as reduced stability, range of motion and significant risk of developing osteoarthritis (Gillquist and Messener, 1999).

Discussion

The injury presented in this case study has shown that certain situations in sport that result in a serious injury are hard to control or prevent. With this particular example the player most likely hyperextended the knee before a lateral impact forcing the knee into internal rotation. During the surgical reconstruction it was observed that the posterolateral bundle had been severed and this concurs with the injury situation as during full extension the posterolateral bundle of fibres of the ACL are at maximal tension, therefore the impact received, while in hyperextension, may have been strong enough to rupture that section of the ligament.

The injury occurred in the 70th minute which agrees with Hawkins et al., (2001) who found that the majority of injuries in football occur in the second half of a match.

During the rehabilitation process the player seemed to respond well to the treatment. Although, there was a moderate to large hamstring/quadricep imbalance observed during isokinetic testing in week 12. This imbalance was large enough to cause concern to the physiotherapist leading the rehabilitation, as it was larger than would have been expected for that time post operation. The player had never used an isokinetic dynometer and it was assumed that the large difference was due to the player being slightly reluctant to fully contract the muscles, with the injury still in the mind. This delayed progression of some rehabilitation activities because the player was instructed that running was still contraindicated at this point, even though he felt strong enough. The player admitted that it was quite mentally challenging at this point. It has been shown that negative mood disturbance, reduced self-confidence, and fear of re-injury may be experienced by athletes returning to sport after ACL reconstruction (Arden, Taylor, Feller, Webster, 2013) and that factors associated with a successful rehabilitation include setting goals and objectives, belief in the efficacy of the treatment, social support and constructive communication (Johnson et, al., 2016, Brewer et al., 2003, Kolt and McEovy, 2003). By setting shorter term goals and focusing more on co-contraction exercises of the knee muscles, the player overcame this issue and when retested for quadricep/hamstring balance in week 16, he was within 10% of the non-injured leg. This was deemed sufficient as the benchmark was a maximum of 15% difference from uninjured side.

The top five risk factors identified in professional football are: fatigue, muscle imbalance, fitness, movement efficiency and previous injury (McCall, Carling, Berthoin, 2014). The most common situation in football that ACL injuries occur during are trunk rotation with a planted foot, regaining balance after kicking and landing awkwardly from a jump (Walden et al., 2015), further highlighting the uncommon nature of the present injury. Although it is very hard to predict or avoid an injury such as this, steps may still be taken to make the occurrence as minimal as possible.

Although some studies report a connection between ACL injury and anatomical, hormonal and genetic factors (Posthumus, September and Keegan, 2009), these are non-modifiable; whereas, biomechanical and neuromuscular components are modifiable therefore should form the basis of a prevention strategy.

A multifaceted program that includes eccentric hamstring exercises along with other training modalities such as plyometrics, balance, resistance and flexibility have been shown to be beneficial in reducing ACL injury risk factors (Monajati, Larumbe, Goss-Sampson and Naclerio, 2016).

Assessing and correcting proper landing mechanics with feedback on technique has also been shown to be effective in improving hip and knee biomechanics (Monajati, Larumbe, Goss-Sampson and Naclerio, 2016). This focuses on eliminating valgus collapse of the knees on landing by strengthening the hip stabilising muscles.

Strengthening exercises that improve the functional hamstring/quadricep strength ratio and promote a shift of optimal knee flexion peak torque toward a more open angle position may also reduce the risk of ACL injury (Monajati, Larumbe, Goss-Sampson and Naclerio, 2016), especially in the injury presented in this case study. The conventional hamstring/quadricep ratio is between 0.6-0.8, indicating that the hamstring should be approximately 60-80% of the strength of the quadricep (Aagaard et al., 1996).

As football is an anterior thigh dominant sport due to the kicking action, it is important to balance strength of the antagonist muscle, in this case the hamstrings. Exercises such as the Nordic curl have been shown to be effective in reducing the rate of overall, new and recurrent hamstring injuries in professional and elite footballers (Petersen, 2011) and increasing eccentric strength of the knee flexors (Iga, Fruer, Deighan, Crox and James, 2012).

Weight bearing functional exercises are emphasized over isolated joint movements because they produce a more stabilizing effect on the knee and diminish ACL strain. This is as a result of muscular co-contractions and muscle recruitment that resembles functional activities. In addition, these exercises stimulate mechanoreceptors throughout the kinetic chain, resulting in adaptation the improves proprioception (Wilk et al., 1997)

Summary

Certain injury situations in football are hard to predict or prevent, but by identifying key risk factors, injury prevention strategies can be put in place in an attempt to minimize these incidents. Regular testing of players will highlight discrepancies in fitness/muscle imbalance and coaching technique in landing mechanics can improve movement efficiency. By identifying risk factors and situations in which this injury occurs, the practitioner can establish effective prevention strategies. Targeting the modifiable risk factors such as biomechanics and neuromuscular adaptation through strengthening and coaching proper technique should be considered when implementing preventative interventions. Ultimately, the compliance of the athlete to the injury prevention protocol is key, and therefore critical for success in reducing the risk of future injury.

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