Introduction on knee and ankle injuries, in particular


Physical activity is very important for
our health and well-being, as well as helping us to maintain a healthy weight.
However, participation in sports comes with a considerable risk of injury, in
particular to elite athletes. According to studies from Scandinavian document,
sport injuries constitute 10-19% of all acute injuries treated in the emergency
room, and the most common types are knee and ankle injuries (R Bahr & T
Krosshaug, 2005). A musculoskeletal injury can be defined as damage sustained
by tissues of the body in response to forces applied through physical trauma.
Biomechanics plays a key role in trying to prevent and treat musculoskeletal
injuries. Biomechanical studies provide information on mechanical loading
during movements, mechanical properties of tissue and preventative or
rehabilitative therapies. For this essay, I will be zoning in on knee and ankle
injuries, in particular ankle sprains and Anterior Cruciate Ligament (ACL)
injuries. The reason for this being that the latter is one of the most severe
injuries an athlete is susceptible to when playing sport and the other is one
of the most frequent across all sports. I will discuss what are the most likely
causes of these injuries and preventative methods. I will also give an insight
into the effects of resistance training on the body’s tissue’s and how this can
lead to injury development.

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Anterior Cruciate Ligament (ACL)

Most musculoskeletal injuries have a
mechanical aetiology (Thor Besier, Stanford
University Medical Centre, 2009). Injuries occur when the force, which
is being applied, exceeds the strength of the tissue, for example, ACL injury.
ACL injuries are a growing cause for concern. Those at the highest risk of an
ACL injury are female athletes who compete in soccer and team handball. They
are 4-6 times more likely to suffer from an ACL injury than their male
counterparts taking part in the same sport and competitions. These types of
injuries are mostly prevalent in pivoting sports such as soccer, football,
basketball and team handball (see fig 1.). ACL injuries are the number one
reason for side-lining athletes in the NFL & NBA (Dr. Hewett, Mayo Clinic, 2015).


The most common type of ACL injury is
via a noncontact mechanism. A noncontact ACL injury occurs as a result of an
awkward movement that doesn’t involve direct contact with another athlete. Most
noncontact ACL injuries occur when the individual is rapidly stopping, landing
from a jump, or suddenly decelerating with a change in direction. An ACL injury
consists of a combination of rotations. The abduction of the distal tibia
combined with an anterior translation of the lateral tibia and an internal
rotation, which leads the ligament to rupture. By taking approaches to limit
these three rotations, we can decrease an athlete’s risk of tearing the
ligament. Studying neuromuscular imbalances that can lead to these rotations
around the joint can help researchers reduce the likelihood of this injury
occurring. The key focus is on the hips and pelvis, making sure that the
athlete activates the gluteal muscles, the biggest and most powerful muscle
group in the body. The gluteal muscles help to resist the dropping in of the
hip and internal rotation of the knee that lead to an ACL injury. Although not
the most frequent injury suffered from participation in sport, ACL injuries
have received great attention. The reason for this being the severity of the
injury. A recovery period ranging between 6 and 12 months is not unusual for
this specific injury.

Prevention Methods

Henning identified three potentially
dangerous movements in sport that should be modified through training in order
to prevent ACL injury. He suggested that upon landing, athletes take up a more
bent-knee position and decelerate before a cutting manoeuvre. These techniques
were implemented in a small pilot sample of athletes and suggested a decrease
in the risk of injury in trained versus untrained participants. Because of this,
Hewett et al. devised a training program, which included an initial phase
devoted to correcting jump and landing techniques in female athletes. Four main
aspects were addressed, which included the following:

Correct posture (i.e.
Chest over knees) throughout the jump

Jumping straight up
with no excessive side-to-side or forward-backward movement

Soft landings,
including tot-to-heel rocking and bent knees

Instant recoil
preparation for the next jump

The women who used the training program
were able to significantly reduce noncontact ACL injuries compared with the
control. These two studies show just how important the incorporation of dynamic
and biomechanically correct movements are in training programs aimed at injury

Numerous studies have shown the effect
of neuromuscular training programs and the effectiveness they have on injury
prevention. These programs focus on strength, balance, and maintaining the
“knee-over-toe” position during dynamic movements. Tests such as drop-jumps and
one-legged squats are very simple and can be used to screen athletes with poor
strength, balance, and “knee-over-toe” control.

Identification of ligament dominance is
another measurement that allows individuals at potential risk of an ACL injury
to be identified. During a single-leg landing, pivoting or deceleration, the
motion of a ligament dominant athlete may be directed by the external ground
forces (GRF) rather than their musculature. This evaluation of an athlete’s
level of ligament dominance can be measured using a simple 31cm box-drop test
combined with a vertical jump. When landing from the box, a ligament-dominant
athlete may display considerable medial linear motion in the coronal plane that
can be identified visually. Certain movement patterns that place an athlete in
a position of high ACL load combined with a poor knee flexion angle may
increase the risk for ligament injury or failure. Ligament dominance can be
addressed by teaching the athlete to control dynamic knee motion, especially
unwanted motions in the coronal plane. This can be achieved through progressive
exercises that challenge the neuromuscular system. The first step to addressing
the ligament dominance is to make the athlete aware of proper technique and
form as well as poor and potentially dangerous positions. In order to do this, athletes
should be placed in front of a mirror or videotaped. The second step involves
critical evaluation. Evaluate the athlete during the jumping and landing
sequences, providing them with constant, technique-orientated feedback. 

The shoe-interaction has also shown to
be a contributing risk factor to ACL injuries. Excessive shoe-floor friction
can be avoided by wearing appropriate shoes on the different playing surfaces.
Some studies of American football athletes have shown that using longer cleats
on artificial turf produced a higher torsional resistance and placed these
athletes at an increased risk of suffering knee injuries.


Ankle Sprain (Lateral Ligament

The ankle on the other hand is the most
common location for injury across all sports (see fig 2.). It’s estimated that
25% of injuries across all sports are ankle related (Tik-Pui Fong et all.
2007). Ankle sprains (damage to the lateral ankle ligaments) account for 85% of
all ankle injuries. The lateral ankle ligaments act as a support mechanism for
the ankle, holding the bones and joint in position. These protect the ankle
from abnormal movements such as excessive turning, twisting and rolling over.
It’s these kinds of movements that lead to ankle sprains. The ligaments are
stretched beyond their normal range in an abnormal position, leading to
overstretching and rupturing of one or more of the lateral ligaments. An ankle
sprain can cause an athlete to refrain from a sporting activity for at least
one day. However, the side effect of this type of injury is the high risk of
re-injury. This can result in disability and chronic pain or instability in
20-50% of recurrent cases. Studies carried out on soccer, volleyball, and
basketball athletes, and military recruits who underwent basic training found
that they were at a twofold risk for lateral ankle ligament injury after
suffering a prior ankle injury. This highlights the importance of identifying
players with a previous injury and/or impaired neuromuscular control, so that
they can be provided with proper treatment and medical guidance.


Prevention Methods

Taping is probably the best known and
widely used preventative measures against ankle sprains. Review of prospective
studies of the effect of taping and bracing on reduction of ankle sprains
reveals positive and consistent findings. Athletes who have a history with
ankle sprains experience a lower occurrence of ankle sprains. Taping is a form
of strapping that is used to maintain a certain joint position. This was the
earliest measure used to prevent ankle sprains. It stimulates additional nerve
receptors on the surface of the ankle to avoid any excessive ankle movements,
which could lead to an ankle sprain. For standard ankle application, the choice
of tape is 3.8 or 5.1cm white porous athletic non-elastic tape. There are many
methods for taping the ankle, but two of the most common and widely used are
the basket weave & the figure 8. Taping isn’t very cost effective and one
of the great benefits is that the method of taping can be adjusted to the needs
of the athlete.

The idea of bracing evolved from ankle
taping. Many athletes at all levels of competition are currently using this
method. They are reusable, self-applied and re-adjustable. Braces are
considered to have many advantages over the traditional method of taping,
however many athletes do not feel as comfortable wearing them. Many studies
have been carried out comparing the taping method to bracing of the ankle. The
general idea of both methods is to prevent excessive plantar flexed inversion
when needed. Previous research shows that the brace has the better mechanical
capabilities in terms of reducing the ankles range of motion. Tape appears to
have an equal restriction directly after being applied, however the mechanical
supports deteriorates after short bouts of exercise. Braces do not show much
loosening and can be easily adjusted during a match.

One measure that has seen extensive
research over recent years is the improvement of neuromuscular function,
specifically balance board training. Trauma to mechanoreceptors of the ankle
ligaments after an ankle sprain can produce a proprioceptive impairment in the
ankle. This could go as far as explaining the risk of re-injury within one year
of an ankle sprain. Neuromuscular training programs are designed for the
rehabilitation after an ankle sprain and aims at improving proprioception by
re-establishing and strengthening the protective reflexes of the ankle. As a
result of this, neuromuscular training is seen as a potentially very effective
measure to reduce the risk of injury reoccurrences. The effect has been shown
in studies from a variety of different sports, which all showed a reduction in
injury risks for players with previous ankle sprains (Tropp et al. 1985,
Verhagen et al. 2004b).    


Resistance Training

The human body contains tissues that are
remarkable in their ability to adapt to imposed stress. German anatomist Julius
Wolff summarized the nature of the response to mechanical stress and stated
that a tissue adapts to the level of stress imposed on it; that is, the level
of adaptation in a tissue reflects the level of typical loading. This is known
as Wolff’s Law. When mechanical stress decreases or is removed, the tissue will
lose strength through atrophy and this causes a decrease in size. Wolff’s
observations were specific to bone, however further studies revealed the law to
be applicable to other connective tissue such as ligament and tendon.

Muscle tissues adapt to resistance
training by increasing cross-sectional area as individual fibres increase in
diameter. The arrangement of collagen and elastin in tendons & ligaments
similarly reflect the exposure to tensile loading and is affected by the level
of training. The level of imposed stress from training can be varied as a
stress continuum. At one end there is the pathologic underload zone (low level)
and at the other is the pathologic overload zone (high level). An active
lifestyle keeps the level of stress with the physiologic loading zone and this
maintains the tissues current status. The tissue will neither get stronger, nor
weaker. When stress is maintained in the physiologic loading zone, the same
force-generating capability is maintained by the muscle, bone mineral content
stays the same, and both ligaments and tendons maintain their ability to
withstand tensile stress.

In the physiologic training zone, a
level of stress is imposed, one which is greater than the tissue has adapted
to. This exceeds the yield strength of the tissue and causes microdamage within
the tissue. The larger the level of stress, the greater the extent of the
microdamage. In response to the microdamage the body begins a rebuilding phase
of the tissue. The time required for this rebuilding is dependent on the extent
of the damage caused. Generally, the greater the damage, the greater amount of
time is required. This rebuilding of the tissue leads to hypertrophy, or
strengthening of tissue, according to Wolff’s Law. Systemic application of
loads in the physiologic training zone is the basis of the overload principle,
which is responsible for causing the cellular and structural changes within a
tissue called the training effect. Systemic loading means that the imposed
tissue loading purposely exceeds the tissue’s yield threshold to cause
microdamage, but allows enough rest time in order for the tissue rebuilding
phase prior to the next session. It is during this time that the muscle fibres
will hypertrophy.

At opposite ends of the continuum are
areas marked distress. These are areas were the levels of stress are either too
high or too low below the physiologic loading zone. Loading of a tissue at
either of these levels will result in changes that compromise tissue function.
Extended periods of inactivity when there is continued low loading applied to a
tissue represents the pathologic underload zone. If this low level of stress is
not raised beyond the underload zone, then a detraining effect will occur. An
unstressed tissue will begin to atrophy and the muscle will waste away. Bone
mineral content decreases, muscle size decreases, and ligaments and tendons
lose their flexibility. These types of tissue changes are apparent when a cast
has been removed from a limb. The immobilized limb will have noticeably
atrophied in comparison to the uninjured limb. A chronically under loaded
tissue will become weak and is more prone to injury as the yield of threshold
of the tissue is reduced.

On the other hand, the pathologic
overload zone represents a level of loading that causes a substantial amount of
damage to a tissue. When a single application of a high level of stress causes
an injury, the injury is referred to as a traumatic injury. This type of injury
occurs in a high-impact collision between two or more objects, such as other
players or objects. For example, a medially directed blow to the knee can
strain the medial collateral ligament. An extended period of recuperation and
rehabilitation is required to return the tissue to a state where activity can
be resumed.   


Unfortunately, injuries are prevalent
throughout sport across all levels of competition. Injury is something that
cannot be avoided. However, through extensive research and by looking at an
athlete’s performance from a biomechanical aspect, the likelihood of injury can
be drastically reduced. As mentioned earlier, ligament dominance is a
contributing factor to ACL injuries, particularly in female athletes. Given the
technology and equipment that’s at researcher’s disposal today, this is
something that can be brought to their attention early on and eradicated to
through an appropriate training program. Training also plays a major role in
injuries, both as a preventative measure and a cause. Neuromuscular training is
a very effective method and has been proven so by numerous studies such as “The
effect of a proprioceptive balance board training program for the prevention of
ankle sprains: a prospective controlled trial” (Verhagen et al. 2004). This
type of training focuses on strength, balance and form. As mentioned earlier
throughout the essay, technique is critical when it comes to preventing injury.
Resistance training can also be very effective when it comes to rehabilitating
the injured muscle, however an improper approach to this can further hamper an
injury, or even cause a fresh one. It’s very important to maintain an
appropriate level of stress and avoid overloading, which can lead to
substantial damage to the tissue. Extensive research has been carried out in
the field of injuries, however there is still plenty more to be done. There
have been some major developments made in recent years, with biomechanics
playing a vital role. 



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