Will the Women’s World Cup be remembered for ACL injuries?
As the Women’s World Cup gets under way in Canada, the opportunity arises to discuss some of the injury problems specific to the female game. In particular, injury to the Anterior Cruciate Ligament (ACL) is common in women’s football despite the skills and demands required for the female game being no different to the men’s. Twisting and turning at high speed; stopping, starting, changing direction, jumping and landing etc. are all essential skills for a footballer to possess; whether male or female. However, in the women’s game the incidence of ACL injury is far greater than in men’s football and can affect players at any level; you don’t have to be at the elite end of the game to suffer a cruciate ligament tear.
Injuries to the ACL usually occur in one of two different ways; either through direct contact with an opponent or team-mate, or by non-contact means such as jumping and landing awkwardly. With the contact method, the injury usually occurs through the mechanism involved in tackling – or being tackled – when the knee twists or gives way as a result of being forced into a position that it isn’t really meant to go into. In these situations it’s usually not only the ACL that sustains the injury, other structures are injured too; such as the menisci (or cartilage as these used to be referred to) and other supporting ligaments of the knee. In women’s football, though, non-contact ACL injuries are generally more common and these tend to occur either on landing or by turning sharply to change direction.
The ACL is one of two ligamentous structures deep within the knee that connects the thigh bone (femur) and shin bone (tibia) with the purpose of preventing excessive knee movement in a backward or forwards direction. Basically, the ACL prevents excessive forwards movement of the tibia on the femur while the Posterior Cruciate Ligament (PCL) prevents excessive backwards movement. A torn or stretched cruciate ligament is therefore associated with an unstable knee. Although the ACL as a structure is rarely injured in isolation, injuries to other ligamentous structures often accompany ACL tears but take less time to heal. The PCL can also be injured in football but is less common.
It’s normally the medial collateral ligament (MCL) which is the most frequent of the knee injuries sustained in football that accompanies ACL sprains. The MCL is the structure that prevents excessive sideward movement in an inward direction and is normally the first part of the knee to give in a block tackle as the impact will often ‘open the joint’. This action stresses the ligament, resulting in a sprain or tearing of the tissue. This normally happens when contact is made with the inside of the foot, resulting in the knee ligaments being stretched or torn as the joint opens as a result. MCLs are injured in exactly the same way if the player in possession of the ball is tackled on the lateral side of the body. This commonly forces the knee to buckle inwards –medially – stressing the MCL in the same way as in the block tackle but from the opposite direction.
Meniscal injuries – or cartilage tears as they used to be called - are caused by excessive rotatory movements; The most common of these mechanisms are if the knee is twisted and / or folded underneath the body when tackling, or by ‘spinning’ around the fixed lower leg such as when taking a swipe at the ball and failing to make proper contact. This can cause a tear in the actual meniscus which often requires surgery. Sometimes the foot just sticks in the ground and the knee twists; this simple movement can result in damage to any or all of the structures mentioned. If all three structures are injured together - ACL, MCL and medial meniscus – this is known as O’Donoghue’s Triad and the recovery period following this injury is lengthy.
O’Donoghue’s Triad usually occurs as a result of a tackle and the rehab period can often reach twelve months on average although variables exist on either side of this time-frame. In football, jumping and landing awkwardly can have the same effect on the ACL as on the meniscus. If you jump and land and the foot sticks, the momentum of the rest of the body can result in the knee giving way, resulting in a tear of the ACL. When this happens, an audible ‘pop’ or ‘cracking’ sound is often heard at the time; followed by immediate swelling and an inability to weight-bear without the knee giving way.
Research has shown over the years that female footballers appear to more susceptible to ACL injury than their male counterparts and that women players are at a higher risk of sustaining these (Dugan, 2005). In a study specifically designed for female athletes commissioned by the International Olympic Committee, leading Swedish sports surgeon Per Renstrom and colleagues reviewed available evidence and found that three main risk factors were the most frequently cited reasons for the high proportion of female footballers suffering ACL injury. Although the study was actually published in early 2011, little concrete evidence has emerged as yet to contradict the findings.
The first risk factor identified by Renstrom et al is often thought to be connected with female biomechanics; women generally have a wider pelvis than men and this leads to an additional load on the knee due to an increased angle between the thigh bone and the shin. This is known as the ‘Q’ angle and is one of the first things that will be identified by a proper biomechanical assessment. An increased ‘Q’ angle can lead to the knee giving way on landing as more of the force of impact is taken through the medial part of the knee.
The ‘Q’ angle is formed by the intersection of two imaginary lines; with the first line starting at the pelvis and extending down the femur through the centre of the patella. Where this line crosses a similar imaginary line drawn upwards through the tibia from the ankle to the patella, identifies the ‘Q’ angle. The wider the hips, the greater the ‘Q’ angle. Female athletes considered to be at risk of injuring their ACLs are said to have an increased ‘Q’ angle, and this leads to an additional strain on the ACL which then becomes more susceptible to being ruptured as a result of a twisting injury.
As the second major risk factor, Yu et al (2002) highlighted that the area of the knee where the ACL inserts on the femur is narrower in women and this also can lead to greater forces on the ligament since there is less space for the ACL to move within the female knee than in the male. Additionally, Yu et al found that altered movement patterns between men and women are likely to place an increased load on the female ACL, leading to a predisposition to injury.
However, it’s not only anatomy and biomechanics that influence ACL injuries in female football; as a third risk factor, hormonal changes are also thought to have an effect on players. Although anatomical and biomechanical influences are known to differ between men and women, Renstrom et al (2008) proposed evidence in support of ACL injuries being sustained during the pre-ovulatory phase of the menstrual cycle compared with the post-ovulatory phase.
A carefully thought-out injury prevention programme considered to reduce the risk of ACL injury in women’s football was suggested by Tyler and McHugh (2001). The idea of such a programme is to gradually alter the way the body lands after jumping. The main thing is to ensure that the front part of the foot lands first before the body weight then transfers to the rest of the foot. The landing needs to be soft, and the knees and hips should flex slightly upon landing. To assist with proper alignment, the knee should be over the centre of the toes as the foot hits the ground.
It’s also thought that the effects of fatigue on female footballers can contribute to injury risk by impairing the muscles of the thigh that provide dynamic knee joint stability (Ortiz et al (2010). Strength-endurance training to help defer the onset of fatigue together with improved body control in jumping and landing could well be the key towards minimising the risk of sustaining ACL injuries in the long-term. Additionally, weakness of the hamstring muscles can contribute to an unstable knee, therefore hamstring muscle strengthening is essential after ACL injury or surgery.
Football’s medical people are also concerned about the number of ACL injury recurrences; plus the number of ACL injuries sustained to the non-dominant leg. The recurrence rate for cruciate ligament tears in female footballers is high; and to date the reasons behind this have not been fully identified. There are girls playing at elite level who have successfully returned to football following not only one ACL tear and subsequent surgery but have then had to deal with the same injury twice, such as Lucy Staniforth of Liverpool for example. Lucy tore her ACL in the Women’s FA Cup final in England two years ago while playing for Bristol Academy and then suffered a similar injury to her other leg after joining Liverpool.
Some players, though, have had as many as four or five ACL injuries; and most of the literature on women’s ACL injuries highlight Amy Steadman who suffered a succession of these, sustaining four ACL tears before she was 21 and forcing early retirement from the game at a very early age. Of the current World Cup players, Canada’s Diana Matheson has only just returned to play and will be hoping that her knee holds up for the tournament; while Ali Krieger sustained her ACL injury in 2012 but has recovered well and is a regular in the USA squad again.
So as we look forward to the next few weeks’ football it will be interesting to see the injury rate in the Women’s World Cup. With the number of games ahead the odds are that somebody will pick up an ACL injury; or worse still will suffer a recurrence of a previous ACL sprain. The evidence says that the biggest single injury risk factor is having sustained a previous injury to the same structure, and with the number of players in this World Cup who have previously undergone ACL surgery there’s a good chance that we’ll see another.
With the recent controversy over having all the games played on artificial surfaces - often cited as being an identifiable risk factor for injury - we certainly hope not; and that the tournament will be remembered purely for footballing reasons and not for the number of injuries sustained.
Dugan SA (2005). Sports-related knee injuries in female athletes: What gives? American Journal of Physical & Medical Rehabilitation. Vol.84; 122 - 130.
Ortiz A, Olson S, Entyre B, Trudelle-Jackson EE, Bartlett W, Venegas-Rios, Heidi L (2010). Fatigue effects on knee joint stability during two jump tasks in women. Journal of Strength and Conditioning Research. Vol. 24 (4); 1019 – 1027.
Renstrom P, Ljunngvist A, Arendt E, Benynnon B, Fukubayashi, Garret W, Georgoulis T, Hewett TE, Johnson R, Krosshaug T, Mandelbaum B, Micheli L, Myklebust, Roos E, Roos H, Schamasch P, Shultz S, Werner S, Wojtys E, Engebretsen L (2008). Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement. British Journal of Sports Medicine. Vol. 42; 394 – 412.
Tyler TF, McHugh MP (2001). Neuromuscular rehabilitation of a female Olympic ice hockey player following anterior cruciate ligament reconstruction. Journal of Sports Physical Therapy. Vol. 31 (10); 577 – 587.
Yu, B; Kirkendall DT, Garrett WE (2002). Anterior Cruciate Ligament Injuries in Female Athletes: Anatomy, Physiology, and Motor Control. Sports Medicine and Arthroscopy Review. Vol. 10 (1); 58 – 68.