The ACL originates on the anterior intercondylar area of the
tibia and inserts on the posteromedial aspect of the lateral femoral
condyle. It is composed of two bundles
of type 1 collagen fibres; an anteromedial bundle (taught in flexion) and a
posterolateral bundle (taught in extension).
The ACL is the primary restraint to anterior translation of the tibia
relative to the femur. It plays a secondary
role in restraining internal rotation particularly when the knee is close to
full extension.
A number of risk factors have been associated with ACL
injuries. They can be divided into 4
categories:
Anatomical
-
Increased BMI
-
Narrow femoral notch width
-
Greater ligament laxity
-
Wider pelvis and Q angle
Hormonal
-
Oestrogen levels during early and late
follicular phase of menstrual cycle
Environmental
-
Harder surfaces
-
Increased shoe-surface friction
-
Cleat position
Neuromuscular
-
Poor ability to control dynamic knee valgus
-
Quads/hamstring ratio
-
Reduced knee and knee flexion angles
Previous ACL injury is also a risk factor for ACL injury for
both the reconstructed or contralateral knee (Orchard et al 2001).
Approximately 70% of ACL injuries are non-contact injuries,
usually seen in sports and activities involving complex movements such as
cutting and pivoting account (e.g. netball, football) (Hernandez, 2006). A non-contact ACL rupture usually involves a
rotational or lateral valgus force on the knee with the knee flexed and the
foot planted. An example of this is the
football player who steps off his foot in a cutting manoeuvre to try and change
direction, only to have his knee buckle underneath him http://www.youtube.com/watch?v=lpIOMuqXWrE
Contact ACL injuries often occur from hyperextenion or valgus forces applied
externally to the knee (e.g. contact from an opponent).
Patients often report hearing a ‘pop’ as the ACL
ruptures. Gross swelling of the knee and
spasm of the hamstrings usually occurs within minutes. Standard assessment involves a stress test
for the ACL – these include Lachman’s, pivot shift and anterior drawer. Unless performed soon after injury, hamstring
spasm can limit the effectiveness of these tests. Patients report pain with knee movement,
decreased ROM and instability of their knee.
MRI is the current gold standard
for diagnostic imaging. This is also
useful to investigate other pathology that may be present such as medial
meniscus injury or MCL tear (unhappy triad).
Whether you can have a partial tear of the ACL also remains
debatable.
Pictures from: http://www.emedx.com/emedx/diagnosis_information/knee_disorders/acl_mri_pictures.htm
ACL tears do not heal after injury. Stitching the ligament back together has
generally failed due to a poor blood supply and poor healing environment
created by the synovial fluid. As a
result, ACL injuries are costly in a number of ways: time lost from sport,
financial costs of rehab and/or surgical repair, long term consequences such as
osteoarthritis, and decreased quality of life.
Which brings up the questions: Can you function without an ACL and what are the consequences of doing
so?
We know the ACL helps with dynamic stability of the knee so
without an ACL the stability of the knee is compromised which potentially MAY
cause further damage such as meniscus tears.
However in some patients, this can be compensated for with good
neuromuscular control.
Eitzen et al (2010) recommend a period of rehab (prehab) to
inform decision making for the management of ACL injury (ie conservative vs
surgical). And what a great idea that is
(no sarcasm intended)! As a sports
physio I often see patients with ACL tears who almost immediately see a surgeon
who operates within days to weeks without any form of prehab. I don’t think this is ideal for a number of
reasons including: a) some patients can function without an ACL, b) prehab
results in better outcomes post-surgery and c) patients can have a false sense
of security that after surgery their knee will be just like new.
Prehab according to Eitzen’s (2010) study should start when
initial impairments have resolved (no joint effusion, no gait abnormalities,
equal ROM, able to hop pain free).
Whether this is suitable criteria remains to be tested. I would think if you can hop pain free you’re
doing ok. Initial testing involved 4
single leg hop tests, self-reported questionnaires, global rating of knee
function, episodes of giving way and isokinetic quads and hammy strength
tests. Eitzen’s prehab program then
involved progressive exercise therapy for 5 weeks (for patients playing level 1
and 2 sports – see table below) followed by retesting. Results from this study found a significant
improvement in knee function in patients with ACL injury suggesting a period of
prehab is important prior to surgery or as the beginning of a progressive
conservative rehab program.
Activity Level & Skill Requirements
|
Level
|
Skills
|
Example Sports
|
|
1
|
Jumping, Cutting, Pivoting
|
Soccer, Netball, Football, Basketball
|
|
2
|
Lateral Movement OR
Heavy manual labour OR working on uneven surfaces
|
Tennis, Skiing
|
|
3
|
Light activity
|
Running, weight lifting
|
|
4
|
Sedentary activity
|
Housework, ADLs
|
Frobell et al (2010, 2013) have shown that delaying
reconstruction does not affect outcomes.
Two year and 5 year data show patients (active, but not elite athletes) who
had early reconstruction (<10wks) did not have better self-reported outcomes
(KOOS) than those who had delayed reconstructions (>5-19mths). As physiotherapists we should be encouraging
a period of prehab prior to any surgery.
This will always be influenced by the athlete, level of sport they play,
demands of other parties (club, coach, sponsors, family), but it is important
to inform the athlete that prehab does improve knee function.
Research is finally coming out comparing the long term
outcomes of patients with ACL injuries that did and didn’t have reconstructive
surgery. Ageberg et al (2008) found no
difference in muscle strength, functional performance (hop tests) or limb
symmetry at 2-5 year follow up. Studies
by Meuffels et al (2009) and Streich et al (2011) also showed no significant
difference in functional outcomes or activities levels at 10 and 15 year follow
ups respectively. Another recent study
from Lynch et al (2013) did show a significantly higher rate of return to level
1 sport in patients with reconstructed ACLs.
It is important to note that patients who had conservative rehab where
advised not to return to level 1 sports.
For years surgeons and physios have advised patients to have
their ACL reconstructed to minimise the risk of osteoarthritis (OA) and further
damage to the knee joint. We now have
some evidence (read above studies) to suggest this may not be true and the
literature is unclear at this point in time whether ACL reconstruction does
reduce OA and meniscus injury rates.
So where does that leave us? Hopefully this flow chart will
help you and your patient make an informed decision:
In my next post I’m going to discuss what should be included
in prehab, rehab and when to return to sport. Questions, comments most welcome on this topic!
LB
References:
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