Anterior Cruciate Ligament (ACL) Injuries

Neil - Doctor of PhysiotherapyBlog, Evidence, Physiotherapy0 Comments

Anterior Cruciate Ligament (ACL) injuries can be a life-defining event for young people. Risk of post-traumatic arthritis skyrockets after an ACL tear in a young person. This creates a huge challenge because they’re too young to have a knee replacement at 30 and their knee-related quality of life is significantly reduced.

Two podcasts this week discuss ACL injuries – causes, rehab and return to sport.

Biomedical engineer Prof Tim Hewett from the Mayo Clinic chats with Assoc. Prof Kate Webster from La Trobe University, and Dr Karen Litzy (DPT) chats with Prof Evangelos Pappas.

Dr. Pappas is critical of physical therapy interventions that do not address deficits that could predispose the athlete to re-injury. He stresses, “Even though it is relatively easy to rehabilitate somebody after an ACL reconstruction in terms of regaining strength, range of motion, and even some proprioception, and even getting them ready for sports, I would strongly argue we are providing a disservice to this patient if we don’t take it a step further and try to identify the biomechanical deficits that would potentially predispose them to an ACL tear and try and rectify those…”

The FIFA 11 + is a successful injury prevention program because it is incorporates an easy-to-follow dynamic warm-up into the daily practices of athletes. “The athlete does a 10 minute warm-up, they will have to do it either way. They have a choice of doing something that is ineffective like static stretching or they have the choice of doing something that is probably a little bit more fun and also effective… The same exercises that prevent the injuries are also good at making athletes run faster or jump higher and have a competitive advantage over their opponents.”

New research has found that athletes who have deficits in the single hop test still present a year post ACL reconstruction have a higher likelihood of re-injury. Dr. Pappas cautions, “Almost nobody should be returning to sport before 9 months after an ACL reconstruction. The knee will feel okay, especially if they had some allograft with no other side morbidity, but it’s the job of the PT to discourage and convince the athlete to not return to sport earlier than 9 months after the ACL reconstruction.”

The vast majority of ACL tears occur during sports, and more commonly in females.

60% of female athletes have 1 or more of 4 biomechanical variables believed to put them at risk of ACL injury:

1. Knee collapsing inwards (valgus)
2. Quad dominance – a straight knee landing strategy
3. Inadequate ability to sufficiently control movement of the trunk relative to the foot – increases load through the knee
4. A side-to-side asymmetry in function – power, strength etc. as demonstrated by a single leg vertical jump

The modifiable biomechanical risk factors are of most interest to the Physiotherapist.

Profs Hewitt and Webster both agree that ACL injuries can be predicted and prevented. “Predict” is based upon a biostatistician’s statistical construct; we cannot predict exactly who will tear their ACL or when, however the data has been shown to be valid and reliable.

– Appropriate neuromuscular training has a 62% relative odds ratio risk reduction in injuries
– In young active adolescents, screening is 80% sensitive and specific in predicting individuals at risk of ACL injury

1. Internal rotation of the hip during take off and landing – 8x greater risk of a second tear
2. Valgus collapse on at least one side – 3x increased risk of a second tear.
3. Side to side asymmetry with relative peak quad to hamstring activation – 3x greater risk of a second tear
4. A ‘stiffening strategy’ evident on a balance test showing tighter less variable movement – 2x greater risk of a second tear

– These four factors account for 94% of the variability and have a 92% sensitivity and 88% specificity for not picking out those individuals who weren’t at relative risk
– 8x increase in second tear returning to sport without first passing objective measures of return to sport
– Hamstring grafts take 18-24 month to heal down to the bone, so if based on time, individuals should not be returning to the same level of play within 2 years!
– Bone scans may be ‘hot’ for 2 years post-injury

Physiotherapist should be addressing the following factors to reduce the risk of injury:

(a) Appropriate distribution of force through lower limb to prevent dynamic valgus, (b) effectively using the glutes and hamstrings as opposed to being quadriceps-dominant during take-off and landing, (c) controlling movement of the pelvis and trunk and (4) equalising the functional capacity between limbs.

Although not yet validated, athletes are at 4x increased risk of re-injury if they have not met all six Return To Sport (RTS) discharge criteria:

– Isokinetic testing (various angles)
– Running t-test
– Single hop
– Triple hop
– Triple crossover hop

On a personal note, I haven’t come across a better way of developing lower limb strength, power and control than with our kettlebell programs. The S.A.I.D. principle suggests that to get better at running, jumping and cutting, athletes must practice those skills, however I’d bet my kids that having a ‘strong’ foundation would reduce the risk far more so than not having it.

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