ACL Injuries: Symptoms, Causes, Treatments
Anterior cruciate ligament (ACL) injuries are on the rise. With increased participation in sports across all ages, in particular an uptake in women’s sport across amateur and professional settings, a greater number of ACL ruptures are being experienced. There have been a large number of scientific studies over the years researching factors behind the increased incidence rate of injuries. However, even though rehabilitation practices have improved over the years, numbers of ACL injury continue to rise.
Even after surgical reconstruction, re-rupture may occur or rupture of the other side. Researchers have shown that in people that have had an ACL reconstruction, the ACL ligament on the other side is at a similar, if not higher risk for injury as the ACL graft of the reconstructed side (Wright 2007). Although this paints a dim picture, there are many things you can do to be proactive about reducing your risk of an ACL rupture, or engaging in full rehabilitation after your injury, to return to full sporting performance. This blog will step you through ACL injuries - the symptoms, causes and treatments, including how to get the most out of your rehabilitation.
This blog will cover the following topics on ACL Injuries:
What is the ACL?
ACL is an abbreviation for Anterior Cruciate Ligament. It is a band of fibrous tissue that connects the femur (thigh bone) to the tibia (shin bone). Its primary job is stabilise the knee against forces that create sliding or twisting forces between the two bones.
Injuries to the ACL occur most often in sports when changing direction or pivoting (twisting force), or when landing or rapidly decelerating (sliding or shear force). Although a direct blow to the knee can injure the ACL, almost 80% of injuries are caused by non-contact events involving a sudden deceleration or change of direction (Renstrom et al 2008).
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What are the signs and symptoms of an ACL rupture?
It is very common to hear a loud 'pop' at the time of an ACL injury, followed shortly by swelling of the knee. The swelling typically happens within the first hour of the injury. You might or might not experience symptoms immediately, but typically within a couple hours of the incident, most will feel pain at the front of the knee, or the whole knee may ache dur to the swelling.
Dependent on the type of injury, there may also be damage to the meniscal tissue (the shock-absorbing cartilage between the bones) or other nearby ligaments, most commonly the medial collateral ligament (the MCL) that stabilises the inner side of the knee joint. In addition, varying levels of bone bruising can also occur which may cause a deep pain in the top of the shin bone (tibial plateau).
Very commonly, the knee will feel unstable, especially as you change direction. On consultation with a health professional, a clinical examination will reveal laxity (excessive movement) at the knee joint. An MRI scan is the gold standard for confirmation of an ACL tear diagnosis.
Causes of ACL ruptures
What causes ACL ruptures? This is the million-dollar question! Unfortunately, not one singular cause can explain the injury - often there may be multiple contributing factors that can play a part in injuries of the ACL.
These factors include:
- Sudden load changes
- Fatigue
- Quadriceps muscle weakness
- Hip strength deficits
- Playing surface
- Footwear
- Cleat selection
Gender is also a risk factor as women are 6 times more likely to sustain an ACL injury then men (Di Paolo 2023)
This gender bias in ACL injuries has contributed to recent increases in injury rates - a greater participation in women’s sports has resulted in higher rates of ACL injuries in athletes.
The injury also has a bigger impact on female sports participation. Currently, only 65% of women return to pre-injury levels of sport, and research shows that men are 1.7 times more likely to return to pre-injury levels and performance (Di Paolo 2023).
Much of the research behind ACL injuries in women is in its infancy, but there has been progress made in understanding why females are at higher risk of ACL injuries.
Female risk factors for ACL injury that have been indicated by the research include the factors below.
Bony factors that may increase risk of ACL injury in females
Firstly, women have different anatomy due to having a wider pelvis, so the femurs (thighs) generally angle in more from the hips towards the knees (they have a larger 'Q-angle' ). This results in higher forces going through the knee joint, and particularly across the ACL.
Higher mobility and ACL injury risk in females
Additionally, women are generally more mobile in their connective tissues and therefore the capsule and ligaments in and around the joints provide less support. The bones are more likely to be able to slide and rotate further on each other, placing higher loads on the cruciate ligaments in the middle of the knees. However, these factors alone are unlikely to explain ACL injuries in isolation.
Hormones and ACL injury risk in females
There is much focus currently on researching the relationship between hormones and injury, with research suggesting that injury rates may be higher in certain phases of the menstrual cycle. More research is required in this field to better understand this relationship (Martin 2021).
What we know so far is that ligaments have oestrogen receptors. High oestrogen levels around ovulation have been linked with reduced ligament 'stiffness', which may leave them more vulnerable to injury at this time of month.
Muscle strength and power, and ACL injury risk
Females tend to have comparatively lower strength and power in relation to body mass index compared to men. Tied into this factor is the development of strength and conditioning programs embedded in sports programs for women. Females in sport have tended to strength train less or been given less opportunity for strength training than their male counterparts. However, this is an easily modifiable risk factor, highlighting the importance of injury prevention programs.
Pain in your knee? Injured yourself playing sport or during a high-impact activity? Did you hear a 'pop' at the time of injury? You could have an ACL Injury!
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Treatment options for ACL ruptures
Following an ACL rupture, most experts agree that commencing a period of rehabilitation early on is the best course of action, regardless of whether you are heading towards surgery or not (Diermeier 2020). It is imperative to restore normal knee function and minimise the loss of quadriceps strength following ACL injury.
There is good evidence to suggest that patients with poorer muscle function in their non-surgical leg early in rehabilitation are less likely to have a successful return to sport (Webster & Feller 2016). So it's really important to make sure you look after both legs in your rehabilitation program.
Younger and more active patients are more likely to re-injury their knee, but this is unlikely to be related to if you have surgery or not. Returning to a higher level of sports is also a risk factor for worse outcomes, as is sustaining additional injury to the meniscus at the same time as the ACL injury. Research has shown that having surgery or not doesn’t seem to affect this outcome (Webster & Feller 2016).
Am I better to have surgery for my ACL tear?
There is currently no clear evidence that having surgery has better outcomes than high quality rehabilitation alone (Frobell 2013). Current evidence also shows that in the longer-term there is no difference in osteoarthritis rates between people who opt for surgical repair and people who don’t. There is more recognition that some people can cope without their ACL and can return to high level sports, however, the research in this space is rapidly evolving with more clarity to come.
At this stage, it is sensible to consider both options with consultation from a sports physician/orthopaedic surgeon and regardless of whether you opt for surgery, it's important to complete a period of rehabilitation immediately after injury.
Rehabilitation for ACL injuries
Regardless of the decision to have surgery or not, the key to long term success with an ACL rupture is high quality rehabilitation. This should include going through a period of criteria-driven rehabilitation with progressive overload to strengthen the muscles of the hip, knee, and ankle. This should be followed by a period of restoring athletic qualities such as plyometric ability and sports specific skills.
A criteria-based rehabilitation process involves having clearly defined check points to graduate from different stages of rehabilitation. This is opposed to a time-based approach which involves simply allowing a period of time to elapse following surgery or injury to guide progress (i.e., running at 3 months). There should be some loose time objective markers, however, ultimately, the decision should be made based on a series of testing (objective strength markers, functional control and hop tests).
Just because you are x-months post injury or surgery, does not mean you are ready to return to sport or higher level challenges. Testing is important to ensure you are ready and safe to progress.
Outlined below is a general overview of a base ACL rehabilitation program, considering an early, mid, and late stage.
Early Stage Rehabilitation:
- Range of motion exercises to restore knee extension (straightening knee) and minimise wasting of quadriceps muscle
- Bicycle work to encourage knee flexion (bend)
- Development of isolated strength of the hip and ankle muscles in addition to muscles around the knee joint (hamstrings, quadriceps, calf)
- Development of compound lifting movements (squat, hinge, lunge)
Mid Stage Rehabilitation:
- Continuation of strength accumulation into heavier based lifts
- Single leg focused exercises (knee extension, single leg squats, single leg RDLs, step ups)
- Development of power and rate of force (early to mid-stage plyometrics)
- Run specific drills mainly focused on straight line running
- Energy system development – building a base of running fitness
Late Stage Rehabilitation:
- Development of reactive strength (drop jumps – rebound like plyometrics)
- Run specific drills progressed to focus on changing direction and agility
- Practising unexpected change of direction (sports-related drills involving ball, etc.)
- Gradual returning to sport-related activity
Returning to sport after an ACL Injury
During the later stages of rehabilitation, the focus turns to decision making around when you should return to sports. In reactional based sports, up to 56% of athletes will not return to sport after an ACL injury (Arden 2011). In addition to this, up to 24% of people re-injure their knee after returning to sport (Grindem 2016) - this is why it's SO important to ensure you are really ready!
As rehabilitation practices continue to improve, these statistics should improve for those who commit to a comprehensive rehabilitation plan. Many people do not complete full rehabilitation, leaving them at higher risk of re-injury.
Optimal rehabilitation should include progressions through the above exercises and ensuring that the athlete is reaching adequate benchmarks (relative to the opposite limb and normative data in similar populations). For example, quadriceps strength measures and hop tests are used to determine readiness of the knee to tolerate impact loads in running.
As mentioned above, the decision making in ACL rehabilitation should primarily be focused on achieving adequate benchmarks to progress between stages and eventually return to play. This is opposed to using a time-based approach. Typically, media will reflect a return to play around 9 months, but two athletes may present differently depending on the structure and commitment to their rehab.
The 9-month mark should be used as a minimum barrier for return to sport, as well as passing readiness criteria. However, the longer you wait, the lower your chances of re-injury. The optimal timeframe for rehab in the non-operative pathway is unclear. If you didn’t have surgery, these time frames are generally shorter but will still be determined once again by the readiness criteria.
Developed pain in your knee after playing sport or after a high impact activity like running? Do the symptoms mentioned in this blog sound similar to your situation? You might have an ACL Injury! Visit us at PhysioTec, and let one of our sports physios provide an assessment and a personalised program to help you get on-top of your injury, and back to doing what you love!
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This blog has been written by one of our experienced PhysioTec physiotherapists. If you would like to book with one of our physio's, call 3342 4284 or click here to book online.
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References:
- Ardern, CL, Webster, KE, Taylor, NF & Feller, JA 2011, ‘Return to sport following anterior cruciate ligament reconstruction surgery: a systematic review and meta-analysis of the state of play’, BJSM, vol 45
- Diermeier, T, Rothrauff, BB, Wilk & KE 2020, ‘Treatment After Anterior Cruciate Ligament Injury: Panther Symposium ACL Treatment Consensus Group’, AOSSM
- Di Paolo, S, Nijmeijer, EM, Bragonzoni, L, Gokleler, A & Benjaminse, A 2023, ‘Definition of High-Risk Motion Patterns for Female ACL Injury Based on Football-Specific Field Data: A Wearable Sensors Plus Data Mining Approach’, Sensors, vol 23, no 4
- Frobell, RB, Roos, HP, Roos, EMR, Roemer, FW, & Ranstam, J 2013, ‘Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial’, BMJ, vol 346
- Grindem, H, Snyder-Mackler, L, Moksnes, H, Engebresten, L & Risberg, MA 2016, ‘Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study’, Br J Sports Med, vol 50, no 13
- Martin, D, Timmins, K, Cowie, C, Alty, J, Mehta, R, Tang, A & Varley, I 2021, ‘Injury Incidence Across the Menstrual Cycle in International Footballers’, Front Sports Act Living, vol 1, no 3
- Webster, KE & Feller, JA 2016, ‘Exploring the High Reinjury Rate in Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction’, Am J Sports Med, vol 44, no 11
- Wright, RW, Dunn, WR, Spindler, KP 2007, ‘Risk of Tearing the Intact Anterior Cruciate Ligament in the Contralateral Knee and Rupturing the Anterior Cruciate Ligament Graft during the First 2 Years after Anterior Cruciate Ligament Reconstruction: A Prospective MOON Cohort Study’, American Orthopaedic Society for Sports Medicine, vol 35, no 7