Medial tibial stress syndrome, commonly referred to as shin splints, is
not considered to be a medically serious condition, however, it can challenge
an athlete’s performance. Approximately 5 percent of all sports injuries are
diagnosed as medial tibial stress syndrome, or MTSS for short.
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Shin splints, or MTSS, occurs most frequently in specific groups of the
athletic population, accounting for 13-20 percent of injuries in runners and up
to 35 percent in military service members. Medial tibial stress syndrome is
characterized as pain along the posterior-medial border of the lower half of
the tibia, which is active during exercise and generally inactive during rest.
Athletes describe feeling discomfort along the lower front half of the leg or
shin. Palpation along the medial tibia can usually recreate the pain.
Causes of MTSS
There are two main speculated causes for medial tibial stress syndrome.
The first is that contracting leg muscles place a repeated strain upon the
medial portion of the tibia, producing inflammation of the periosteal outer
layer of bone, commonly known as periostitis. While the pain of a shin splint
is felt along the anterior leg, the muscles located around this region are the
posterior calf muscles. The tibialis posterior, flexor digitorum longus, and
the soleus all emerge from the posterior-medial section of the proximal half of
the tibia. As a result, the traction force from these muscles on the tibia
probably aren’t the cause of the pain generally experienced on the distal
portion of the leg.
Another theory of this tension is that the deep crural fascia, or the
DCF, the tough, connective tissue which surrounds the deep posterior muscles of
the leg, may pull excessively on the tibia, causing trauma to the bone.
Researchers at the University of Honolulu evaluated a single leg from 5 male
and 11 female adult cadavers. Through the study, they confirmed that in these
specimens, the muscles of the posterior section of muscles was introduced above
the portion of the leg that is usually painful in medial tibial stress syndrome
and the deep crural fascia did indeed attach on the entire length of the medial
tibia.
Doctors at the Swedish Medical Centre in Seattle, Washington believed
that, given the anatomy, the tension from the posterior calf muscles could produce
a similar strain on the tibia at the insertion of the DCF, causing injury.
In a laboratory study conducted using three fresh cadaver specimens,
researchers concluded that strain at the insertion site of the DCF along the
medial tibia advanced linearly as tension increased in the posterior leg muscles.
The study confirmed that an injury caused by tension at the medial tibia was
possible. However, studies of bone periosteum on individuals with MTSS have yet
to find inflammatory indicators to confirm the periostitis theory.
The second theory believed to cause medial tibial stress syndrome is
that repetitive or excessive loading may cause a bone-stress reaction in the
tibia. When the tibia is unable to properly bear the load being applied against
it, it will bend during weight bearing. The overload results in micro damage
within the bone, not just along the outer layer. If the repetitive loading
exceeds the bone’s ability to repair, localized osteopenia can occur. Because
of this, some researchers consider a tibial stress fracture to be the result of
a continuum of bone stress reactions that include MTSS.
Utilizing magnetic resonance imaging, or MRI, on the affected leg can often
display bone marrow edema, periosteal lifting, and areas of increased bony
resorption in athletes with medial tibial stress syndrome. This supports the
bone-stress reaction theory. An MRI of an athlete with a diagnosis of MTSS can
also help rule out other causes of lower leg pain, such as a tibial stress
fracture, deep posterior compartment syndrome, and popliteal artery entrapment
syndrome.
Risk factors for MTSS
While the cause, set of causes or manner of causation of MTSS is still
only a hypothesis, the risk factors for athletes developing it are well-known. As
determined by the navicular drop test, or NDT, a large navicular drop
considerably corresponds with a diagnosis of medial tibial stress syndrome. The
NDT measures the difference in height position of the navicular bone, from a
neutral subtalar joint position in supported non-weight bearing, to full weight
bearing. The NDT explains the degree of arch collapse during weight bearing.
Results of more than 10 mm is considered excessive and can be a considerable risk
factor for the development of MTSS.
Research studies have proposed that athletes with MTSS are most
frequently female, have a higher BMI, less running experience, and a previous
history of MTSS. Running kinematics for females can be different from that of
males and has often been demonstrated to leave individuals vulnerable to suffer
anterior cruciate ligament tears and patellofemoral pain syndrome. This same
biomechanical pattern may also incline females to develop medial tibial stress
syndrome. Hormonal considerations and low bone density are believed to be
contributing factors, increasing the risk of MTSS in the female athlete as
well.
A higher BMI in an athlete demonstrates that they have more muscle mass
rather than being overweight. The end result, however, is the same in that the
legs bear a considerably heavy load. It’s been hypothesized that in these
cases, the bone growth accelerated by the tibial bowing may not advance quickly
enough and injury to the bone may occur. Therefore, those with a higher BMI may
need to continue their training programs gradually in order to allow the body
to adapt accordingly.
Athletes with less running experience are more likely to make training
errors, which may be a common cause for medial tibial stress syndrome. These
include but are not limited to: increasing distance too quickly, changing
terrain, overtraining, poor equipment or footwear, etc. Inexperience may also
lead the athlete to return to activity before the recommended time, accounting
for the higher prevalence of MTSS in those who had previously experienced MTSS.
A complete recovery from MTSS can take from six months up to ten months, and if
the original injury does not properly heal or the athlete returns to training
too soon, chances are, their pain and symptoms may return promptly.
Biomechanical Analysis
The NDT is used as a measurable indication of foot pronation. Pronation
is described as a tri-planar movement consisting of eversion at the hindfoot,
abduction of the forefoot and dorsiflexion of the ankle. Pronation is a normal
movement of the body and it is absolutely essential in walking and running.
When the foot impacts the ground at the initial contact phase of running, the
foot begins to pronate and the joints of the foot acquire a loose-packed
position. This flexibility helps the foot absorb ground reaction forces.
During the loading response phase, the foot further pronates, reaching
peak pronation by approximately 40 percent during stance phase. In mid stance,
the foot moves out of pronation and back to a neutral position. During terminal
stance, the foot supinates, moving the joints into a fastened position, creating
a rigid lever arm from which to generate the forces for toe off.
Starting with the loading response phase and throughout the rest of the
single leg stance phase of running, the hip is stabilized and supported as it is
extended, abducted and externally rotated by the concentric contraction of the
hip muscles of the stance leg, including the gluteals, piriformis, obturator
internus, superior gemellus and inferior gemellus. Weakness or fatigue in any
of these muscles can develop an internal rotation of the femur, adduction of
the knee, internal rotation of the tibia, and over-pronation. Overpronation
therefore, can be a result of muscle weakness or fatigue. If this is the case,
the athlete may have a completely normal NDT and yet, when the hip muscles
don’t function as needed, these can overpronate.
In a runner who has considerable overpronation, the foot may continue to
pronate into mid stance, resulting in a delayed supination response, causing
for there to be less power generation at toe off. The athlete can make the
effort to apply two biomechanical fixes here that could contribute to the
development of MTSS. First of all, the tibialis posterior will strain to
prevent the overpronation. This can add tension to the DCF and strain the
medial tibia. Second, the gastroc-soleus complex will contract more forcefully
at toe off to improve the generation of power. However, it’s hypothesized that
the increased force within these muscle groups can add further tension to the
medial tibia through the DCF and possibly irritate the periosteum.
Evaluating Injury in Athletes
Once understood that overpronation is one of the leading risk factors
for medial tibial stress syndrome, the athlete should begin their evaluation
slowly and gradually progress through the procedure. Foremost, the NDT must be
performed, making sure if the difference is more than 10mm. Then, it’s
essential to analyze the athlete’s running gait on a treadmill, preferably when
the muscles are fatigued, such as at the end of a training run. Even with a
normal NDT, there may be evidence of overpronation in running.
Next, the athlete’s knee should be evaluated accordingly. The specialist
performing the evaluation should note whether the knee is adducted, whether the
hip is leveled or if either hip is more than 5 degrees from level. These can be
clear indications that there is probably weakness at the hip. Traditional
muscle testing may not reveal the weakness; therefore, functional muscle
testing may be required.
Additionally, it should be observed whether the athlete can perform a
one-legged squat with arms in and arms overhead. The specialist must also note
if the hip drops, the knee adducts and the foot pronates. Furthermore, the
strength of the hip abductors should be tested in side lying, with the hip in a
neutral, extended, and flexed position, making sure the knee is straight. All
three positions with the hip rotated in a neutral position and at end ranges of
external and internal rotation should also be tested. Hip extensions in prone
with the knee straight and bent, in all three positions of hip rotation:
external, neutral and internal can also be analyzed and observed to determine
the presence of medial tibial stress syndrome, or MTSS. The position where a
healthcare professional finds weakness after the evaluation is where the
athlete should begin strengthening activities.
Treating the Kinetic Chain
In the presence of hip weakness, the athlete should begin the strengthening
process by performing isometric exercises in the position of weakness. For
example, if there is weakness during hip abduction with extension, then the
athlete should begin isolated isometrics in this position. Until the muscles consistently
activate isometrically in this position for 3 to 5 sets of 10 to 20 seconds
should the individual progress to adding movement. Once the athlete achieves
this level, begin concentric contractions, in that same position, against
gravity. Some instances are unilateral bridging and side lying abduction.
Eccentric contractions should follow, and then sport specific drills.
In the case that other biomechanical compensations occur, these must
also be addressed accordingly. If the tibialis posterior is also displaying
weakness, the athlete should begin strengthening exercises in that area. If the
calf muscles are tight, a stretching program must be initiated. Utilizing any
modalities possible might be helpful towards the rehabilitation process. Last
but not least, if the ligaments in the foot are over stretches, the athlete
should consider stabilizing footwear. Using a supported shoe for a temporary
period of time during rehabilitation can be helpful to notify the athlete to
embrace new movement patterns.
MTSS and Sciatica
Medial tibial stress syndrome, otherwise known as shin splints,
ultimately is a painful condition that can greatly restrict an athlete’s
ability to walk or run. As mentioned above, several evaluations can be
performed by a healthcare professional to determine the presence of MTSS in an
athlete, however, other conditions aside from shin splints may be causing the
individuals leg pain and hip weakness. That is why it’s important to also visit
additional specialists to ensure the athlete has received the correct diagnosis
for their injuries or conditions.
Sciatica is best referred to as a set of symptoms that originate from the
lower back and is caused by an irritation of the sciatic nerve. The sciatic
nerve is the single, largest nerve in the human body, communicating with many
different areas of the upper and lower leg. Because leg pain can occur without
the presence of low back pain, an athlete’s medial tibial stress syndrome could
really be sciatica originating from the back. Most commonly, MTSS can be
characterized by pain that is generally worse when walking or running while
sciatica is generally worse when sitting with an improper posture.
Regardless of the symptoms, it’s essential for an athlete to seek proper
diagnosis to determine the cause of their pain and discomfort. Chiropractic
care is a popular form of alternative treatment which focuses on
musculoskeletal injuries and conditions as well as nervous system disorders. A
chiropractor can help diagnose an athlete’s MTSS as well as overrule the
presence of sciatica as a cause of the symptoms. In addition, chiropractic care
can help restore and improve an athlete’s performance. By utilizing careful
spinal adjustments and manual manipulations, a chiropractor can help strengthen
the structures of the body and increase the individual’s mobility and
flexibility. After suffering an injury, an athlete should receive the proper
care and treatment they need and require to return to their specific sport
activity as soon as possible.
Chiropractic and Athletic Performance
In conclusion, the best way to prevent pain from MTSS is to decrease the athlete’s risk
factors. An athlete should have a basic running gait analysis and proper shoe
fitting as well as include hip strengthening in functional positions as part of
the strengthening program. Furthermore, one must ensure the athletes fully
rehabilitate before returning to play because the chances of recurrence of
medial tibial stress syndrome can be high.
By Dr. Alex Jimenez
