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Final Class Project
External
Rotation
Straight
PRF 720 Essentials of Human Movement Science
From the information provided, we can see that the client demonstrates bilateral
lower extremity external rotation and bilateral flattening of the medial longitudinal arch
or pes planus. Pes planus can cause the plantar fascia to be overstretched due to the
subtalar joint being excessively pronated, causing a rearfoot valgus posture. There will
also be a compromise of the foot’s ability to adequately transfer normal loads. Excessive
or poorly controlled pronation at the subtalar joint is often associated with abnormal
kinematics throughout the stance phase of walking. If the client excessively pronates late
into the stance phase, they will have difficulty stabilizing the midfoot. During the later
part of the stance phase, the midfoot and forefoot must be stable or rigid to accept the
stresses during push off. This stability is normally provided by activation of muscles and
tension in the medial longitudinal arch. Increasing tension in the arch occurs through the
windlass effect, demonstrated while standing on the tiptoes. Without an effective medial
longitudinal arch, the midfoot and forefoot sag under body weight. As a result, the
reduced hyperextension of metatarsophalangeal joints limits usefulness of the windlass
effect for stretching the plantar fascia.
Active forces from intrinsic and extrinsic muscles will have to compensate for
lack of tension produced in the overstretched connective tissues, which may contribute to
fatigue and overuse symptoms. This will require excessive activity from muscles of the
foot, especially the tibialis posterior, to reinforce the medial longitudinal arch. Normally,
the peroneus longus and tibialis posterior muscles should form a functional sling that
supports the arches. As the entire foot contacts the ground, the tibialis posterior should
decelerate the pronating rearfoot by controlling subtalar joint eversion and internal
rotation of the tibia. In addition, the tibialis posterior should eccentrically decelerate
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mid-tarsal joint pronation (assisted by soleus and anterior tibialis), and assist in the
controlled lowering of medial longitudinal arch. During midstance, the tibialis posterior
concentrically externally rotates the tibia. Throughout the mid- to late stance phase, the
tibialis posterior, flexor hallucis longus and flexor digitorum longus should help guide the
rearfoot toward supination as the lower leg externally rotates. A healthy tibialis posterior
works synergistically with the soleus, flexor digitorum longus and flexor hallucis longus
to decelerate the forward momentum of the lower leg. This client’s dropped medial
longitudinal arch is causing an overload of the tibialis posterior. The overload on the
tibialis posterior now increases the frontal and transverse plane stress up the chain and
into the knee.
The effects of pes planus and excessive pronation can cause several chain
reactions at the knee and hip, including increased genu valgum, increased Q-Angle and
coxa vera at the hip. The increase of valgus stress on the medial knee (genu valgum) can
lead to increased stress to the Medical Collateral Ligament (MCL), semimembranosus
and Pes Anserinus Group (sartorius, gracilis and semitendonosus). The now tightened
and stressed MCL, semimembranosus and Pes Anserinus Group are no longer able to
adequately help eccentrically resist or limit tibial external rotation forces and torques or
concentrically internally rotate the tibia. The weakened internal rotators allow the
external rotators to become dominant. In addition, the valgus stress on the knee causes
an increase of compression forces on the lateral compartment of the knee. This can affect
the short head of the biceps femoris’ ability to properly concentrically externally rotate
the tibia and eccentrically internally rotate the lower leg during mid-stance. Therefore, it
is possible that a tight lateral hamstring will not allow complete internal rotation to occur.
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If the medial and lateral hamstrings are tight, they will ultimately restrict the ability of the
pelvis to rotate on the femur. In the closed kinetic chain, the pelvic rotation over a fixed
femur, particularly internal rotation, enables the gluteus maximus to “prestretch” and the
stored elastic energy can then convert to greater force production. This overload or
tightness of the hamstring muscles (semitendonosus, semimembranosus and biceps
femoris) could be the cause of the client’s soreness in the left hamstring.
The overload and soreness of the hamstrings may affect their ability to
dynamically stabilize the lumbo-pelvic-hip complex and assist in hip extension. There is
also a stress placed on the lumbo-pelvic-hip complex in the transverse plane from an
overloaded tibialis posterior. The overactivity of the gracilis decreases frontal plane
stability and affects dynamic stabilization of the hip as well. The gluteus maximus and
adductor magnus (posterior head) must compensate for the hamstring tightness to achieve
hip extension. The hip extensor muscles and abdominal muscles have a synergistic
action as a force-couple that tilt the pelvis posteriorly. When working properly, the
anterior abdominal muscles pull upward via their origin on the anterior pelvis, and the
hamstring muscles pull downward via their origin on the ishial tuberosity of the pelvis,
thus acting as a force-couple that tilts the pelvis posteriorly. Studies show that decreased
activity of one muscle of the force-couple is accompanied by an increase in the activity of
the other. The reciprocal participation contributes to muscle imbalances by reinforcing
the demands on the stronger muscle and minimizing the demands on the weaker muscle.
In the case of the hamstring and abdominal force couple with this client, the abdominals
will increase activity to compensate for the decreased activity in the hamstrings.
Between the increased activity of the abdominals and the tight hamstrings, the pelvis
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could start to excessively rotate posterior, which alters length tension relationship of the
entire lumbo-pelvic-hip complex.
The excessive posterior tilt of the pelvis can place the posterior shoulder
musculature on stretch due to upper thoracic compensations for the loss of lumbar
lordosis. This could affect the serratus anterior’s ability to hold the scapula flat to the rib
cage. Deficient control by the serratus anterior can cause impairments in timing and
range of scapular motion, which can cause stress at the glenohumeral (GH) joints
resulting from incorrect positioning of the glenoid for GH joint motion when there’s
insufficient abduction and upward rotation of the scapula. A weakened serratus anterior
could also cause a “winging scapula”. With a winging scapula, the deltoid and
supraspinatus have an overall line-of-force that rotates the scapula downward. This
motion is associated with an overshortening of the GH abductors, which reduces maximal
force potential. The combination of the downward rotation of the scapula and the
reduced force output, decreases range of motion and torque potential of the elevating
arm. Without normal upward rotation of the scapula, the acromion is more likely to
interfere with the arthrokinematics of the abducting humeral head. In the same sense, by
the rhomboids being put on stretch, their ability to retract and downwardly rotate the
scapula could be affected, as well as decrease scapular stability, which increases stress to
the rotator cuff musculature.
It is important to have the ability to use the entire kinetic chain, coordinating the
hips to help the shoulder. Functioning normally, the serape effect concept helps achieve
this balance. By definition, a serape is a garment that was worn by Latin Americans,
designed to drape around the shoulders from one hip to the other. Thus, it crosses the
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body in a diagonal fashion. The connection from the hip to the shoulder is corresponding
to the muscles of the trunk and their ability to help rotation occur within the trunk. These
muscles are the rhomboids, serratus anterior and the external/internal obliques.
Collectively, contractions of these muscles cause motion from the lumbo-pelvic complex
to the thoracic spine and eventually to the shoulder girdle. The serape effect involves two
systems of the body, the Anterior Oblique System (AOS) and the Posterior Oblique
System (POS). The AOS contains the external oblique and the opposite adductors of the
hip, while the POS contains the latissimus dorsi and the contralateral gluteus maximus.
The fascial connections between these two systems are in a diagonal fashion, which helps
assist stability, power and deceleration from the lower to upper trunk. There is an
interaction between the pelvic girdle on the left and the limb on the right by way of
concentric contraction of the left internal oblique, right external oblique and serratus
anterior on the right. The pelvic girdle is rotating to the left while the rib cage is rotating
to the right. In ballistic actions, the serape muscles add to the summation of internal
forces. They also transfer internal forces from the trunk into the limbs. This justifies
how a tight left hamstring can eventually cause compensations in the right shoulder via
the serape effect.
In closing, we can see that a dysfunction in the foot, such as this client’s dropped
medial longitudinal arch and external rotation of the lower leg, can upset the entire
Human Movement System. The client’s inability to adequately use the entire body to
generate efficient movement will contribute to numerous problems, including the
soreness in the left hamstring and the right shoulder pain that this particular client is
experiencing.
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References
Neumann, D. Kinesiology of the Musculoskeletal System: Foundations for Physical
Rehabilitation. Mosby: St. Louis. 2002.
Sahrmann, S. Diagnosis and Treatment of Movement Impairment Syndromes. Mosby:
St. Louis. 2002.
Vleeming, A. Movement, Stability, and Low Back Pain. Churchill Livingstone: London,
England. 1997.
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