The challenge to rehab and medical professionals is to ensure that players returning from ACL surgery do so with the minimal risk of sustaining a further injury (Bien and Dubuque, 2015).
Anterior cruciate ligament (ACL) injuries in women’s football are known to have a significantly higher rate of recurrence than in men's football (Allen et al., 2007; Gans et al., 2018; Prodromos et al, 2007; Walden et al, 2011).
Various authors have reported that the actual re-injury rates have ranged from 1 in 4 to 1 in 17 in ACL rehabilitated patients (Paterno et al, 2010) with a higher incidence reported in the first two years post-injury (Wright et al, 2007).
Reinjury rates are also higher in female athletes younger than 25 years and with smaller primary grafts often less than 8 mm in diameter (Nguyen, 2016).
Even after successful primary reconstruction, Allen et al., (2016) reported that 28% of all female soccer players and 34% of reconstructed players who returned to sport subsequently sustained a second ACL tear.
Yet despite our best efforts, developing a uniform protocol to prevent this is something that has been discussed for years and numerous theories have been presented as a result.
ACL injuries sustained through a specific series of non-contact mechanisms associated with jumping and landing, running or twisting the knee during a change of direction have been shown to form 70% of ACL tears in women’s football (Burnham and Wright, 2017).
So it would follow, therefore, that preventative strategies are needed to focus on (among other areas) balance, co-ordination, and that explosive burst of speed required that often accompanies directional changes.
Authors agree that ACL rupture often results from repetitive biomechanical stresses leading over time to imbalances in the muscles acting on the knee coupled with reduced neuromuscular coordination.
This is thought to lead to a weakness of the ACL itself which then likely becomes the main predisposing risk factor for injury.
But in practice, the challenges of ACL rehabilitation in the real world can often be a far cry from the published literature, not least when players are coming back from injury and supervised rehab can be difficult to arrange and maintain.
Key to minimising the risk of non-contact ACL injury is thought to be by achieved by gradually altering the way the body lands after jumping, and in women's football at least, this is where the main predisposing factors come into play (Yu et al., 2002).
Risk factors are thought to arise from the angles of the hip and knee on landing; particularly if the knee is almost fully extended and in a valgus position.
The mechanics of a stiff knee landing on a planted foot coupled with increased rotation at the hip (which increases the valgus stress) can be magnified by a forceful eccentric quadriceps contraction leading to overload on the ACL; leading to a subsequent tear (Chappell et al., 2002; Myer et al., 2011; Leppanen et al., 2016).
In short, the landing needs to be soft; and although the knees and hips should flex slightly upon making contact with the ground, the knee should also be over the centre of the toes as the foot hits the surface to assist with proper alignment of the lower limb as a whole (Tyler and McHugh, 2001).
The front part of the foot should take the bulk of the landing force and as the hip and knee flex, as described above, the bodyweight then transfers to the rest of the foot.
Sutton and Bullock (2013) agreed that neuromuscular and proprioceptive training actively encourages female players to avoid placing their knees in vulnerable positions on landing.
Developing the reactive coordination of the hip and gluteal muscles is one area essential for reducing the load on the knee in twisting and turning manoeuvres in a similar vein and emphasises the theory described above.
Linking into this is the thought that the effects of fatigue can contribute to injury risk by impairing the muscles of the thigh that provide the dynamic knee joint stability required (Ortiz et al, 2010 De Ste Croix et al., 2015).
Strength-endurance training to help defer the onset of fatigue together with improved body control in jumping and landing could well be the key to minimising the risk of sustaining ACL injuries in the long-term.
As fine as it sounds in theory, though, training the body to biomechanically adapt is not something that can be done overnight.
This requires regular meticulous attention and the best approach is simply to ensure that jumping and landing techniques are included as an integral part of a regular training session.
Clubs nowadays place a huge emphasis on preventative techniques and are managing to schedule these into their sessions, but if for any number of reasons this does not happen, then it falls to players themselves to work on preventative strategies.
Prevention of ACL injuries certainly isn't easy to implement nor its success guaranteed!
And of course, there are so many other risk factors to take into account as well. In addition to biomechanics, we have the ever-present risk of fatigue, and the original risk factors mentioned earlier related to gender differences and the menstrual cycle.
However, with the amount of research that has been done over the years, we should in theory at least be seeing a greater reduction in female ACL tears.
Sugimoto et al (2015) consider that evidence-based medicine should be practised instead of only considered as "just a concept,” and argue that it is time to translate documented evidence of ACL prevention strategies into actual practice.
This is where the terminology becomes open to debate. Can you really 'prevent' injuries or should we be talking about ‘minimising risk factors’ instead?
Over time I’ve come to think that ‘minimising the risk of injury’ is a more accurate and realistic expression and sits better with players rather than promising injuries won’t occur despite our best efforts to avoid them.
It was Bahr and Krosshaug (2010) who stated that a combination of various factors will render an athlete susceptible to injury, but it is the sum of their interaction that prepares the athlete for an injury to occur in a given situation.
So if we are looking at the high number of recurrences of ACL injuries associated with previous surgery; the potential for another injury always needs to be considered as the various stages of rehabilitation unfold.
It's hard to predict when the circumstances may conspire to lead to the situation described above by Bahr and Krosshaug, especially with so many interlinking risk factors for recurrent ACL prevalent at any given time.
Perhaps we need to re-think our criteria for progression in rehabilitation and consider whether players are ready to move on to the next stage or if current achievements need to be consolidated first; even if that means a longer rehabilitation period is required than originally anticipated.
Over the years, perhaps more research has been conducted into ACL injuries than any other orthopaedic problem. This research has varied between the treatment and management of ACL tears in identifying the causes and mechanisms of injuries.
So although the focus on research has increased our subject knowledge, the high rate of ACL injuries – and in particular recurrences of ACL injuries - remains a cause for concern.
As highlighted by Nilstad et al, (2014) we need to put our increased knowledge of risk factors for lower extremity injuries to better use, and in doing so, continue to develop more highly-accurate and targeted strategies to minimise ACL injury rates in female footballers.
Perhaps we need to go a stage further. In addition to developing injury prevention programmes and identifying common risk factors, further studies are required to assess the effectiveness of current rehabilitation strategies in ACL injury management.
More follows on this fascinating and important subject of ACL injuries in women’s football shortly…
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