Small Group Session II

(answers are shown in red)

Limbs

Review the stages of the gait cycle in preparation for this session.

GAIT CYCLE - JOINT POSITION:

Joint	Heel Strike	Mid-stance	Toe-Off	Swing
Hip	Flexed	Neutral	Extended	Flexed
Knee	Flexed	Extended	Flexed	Flexed
Ankle	Neutral	Dorsiflexed	Plantar Flexed	Neutral

GAIT CYCLE - MUSCLE ACTIONS:

Joint	Acceleration to Heel Strike	Heel Strike to Mid-stance	Mid-stance to Toe-Off	Toe-Off to Acceleration
Hip	Gluteus Maximus Hamstrings Gluteus medius & minimus	Gluteus medius & minimus	xxxxx	Adductors Iliopsoas
Knee	Quadriceps femoris	Quadriceps femoris	Gastrocnemius	Gastrocnemius
Ankle	Tibialis anterior Extensor digitorum longus Extensor hallicus longus Fibularis tertius	Gastrocnemius Soleus	Gastrocnemius Soleus	Tibialis anterior Ext. digitorum longus Ext. hallicus longus Fibularis tertius

Italics = Eccentric Contractions

Problem 1
Examine the action of the hip joint throughout the gait cycle and explain the following:

a. What is the position of the hip joint during each interval of the gait cycle?

See chart on Joint Position.

b. In which interval is the hip in its most stable configuration?

The most stable position of the hip is the extended position. The attains a neutral position
during the interval between hell strike and mid-stance. Between mid-stance and toe-off,
the hip goes from a neutral position to an extended position. It is at this interval that the
hip is most stable.

c. What are the factors responsible for bringing the hip into the stable position and what
factors are responsible for maintaining the hip in its stable configuration?

The non-reference limb is in swing when the reference limb goes into mid-stance. The
forward movement of the opposite (non-reference limb) drags that side of the torso past
the limb as a step is taken. This forces the hip on the reference side into first a neutral
position and then an extended one. Thus, the force that places the reference limb into
extension is a passive one resulting from the movement of the opposite side of the body.
The only muscles acting on the hip during the interval between hell strike and midstance
are the gluteus medius and minimus. These muscles contract concentrically but from
a weight bearing position on the reference or support side to balance the opposite hip,
which is in non-weight bearing position.

d. Identify those muscles acting on the hip during each interval and tell if they are acting
in a concentric or eccentric manner.

See chart on Muscle Actions.

e. What symptoms would you expect to see if there was a lesion of the superior gluteal
nerve? What if the obturator nerve were lesioned?

A lesion of the superior gluteal nerve will result in paralysis of the gluteus medius and
minimus muscles. These muscles act as hip abductors and help prevent the hip from
tilting to far downward when the reference limb is in non-weight bearing position. During
the interval between heel strike and mid-stance, the reference limb is in stance phase and
weight bearing. The opposite limb is entering swing phase and is non-weight bearing.
When this happens, the abductors on the reference (support) side has to act to prevent
the hip on the non-support side from sagging downward. If the gluteus medius and
minimus on the support side cannot act, the non-support hip tilts downward. The person
must bend the torso to the support side to compensate and to allow the limb to swing
forward. This is called Trendelenburg Gait.

A lesion of the obturator nerve on the reference side results in a "waddling" type of gait.
The obturator nerve supplies the hip adductors. These muscles contract concentrically
during the interval between toe-off and swing. During this interval, the hip flexors also
contract concentrically to move the reference forward, a movement that will result in a
step forward. At the same time, the adductors act and draw the swinging limb toward
the midline. This enables the reference limb to hit the ground in front of the non-reference
limb. In effect, as a step is taken, we transfer weight from one limb to the other. If the
limbs are close to each other, the transfer is done easily. Without the action of the
adductors, the reference limb would come down parallel to the shoulder and would be
far from the opposite limb making weight transfer less effective. Try walking by keeping
one foot parallel to your shoulder and you'll see what a waddling type of gait feels like.

Problem 2
Examine the action of the knee joint throughout the gait cycle and explain the following:

a. What is the position of the knee joint during each interval of the gait cycle?

See chart on joint position.

b. In which interval is the knee in its most stable configuration?

The most stable position of the knee is the extended position. The knee attains this
position during the interval between hell strike and mid-stance. At mid-stance, the knee
is in its most stable configuration.

c. What are the factors responsible for bringing the knee into the stable position and what
factors are responsible for maintaining the knee in its stable configuration?

As in Problem 1, the factors responsible for bringing the knee into extension are primarily
passive. The non-reference limb is in swing when the reference limb goes into mid-stance.
The forward movement of the opposite (non-reference limb) drags that side of the torso
past the limb during the process of taking a step. This forces the knee on the reference
side into an extended position. The concentric contraction of the quadriceps femoris also
helps bring the knee into an extended position during this interval. The knee joint is
maintained in the stable configuration by the tightening of the cruciate and collateral
ligaments and the close-packed position of the femoral and tibial condyles.

d. Identify those muscles acting on the knee during each interval and tell if they are acting
in a concentric or eccentric manner.

See chart on Muscle Actions.

e. What are symptoms would you expect to see if there was a lesion of the femoral nerve?

A lesion of the femoral nerve will result in paralysis of the quadriceps femoris muscles.
These muscles act as knee extensors. They contract eccentrically when the reference limb
goes into heel strike to resist excessive knee flexion during this interval. These muscles
act concentrically during the interval between heel strike and mid-stance. The major
problem that involves a femoral nerve lesion is that the quadriceps femoris can no longer
restrain excessive knee flexion when the reference limb goes into heel strike. To compen-
sate, the person usually takes small steps, comes down in mid-stance rather than heel
strike, and bends the torso forward to place the center of gravity in front of the knee. The
latter activity helps place most of the weight of the body in front of the knee helping to
force the knee into extension.

Problem 3
Examine the action of the ankle joint throughout the gait cycle and explain the following:

a. What is the position of the ankle joint during each interval of the gait cycle?

See chart on Joint Position.

b. In which interval is the ankle in its most stable configuration?

The most stable position of the ankle joint is the dorsiflexed position. The ankle attains
this position during the interval between heel strike and mid-stance. At mid-stance, the
ankle is in its most stable.

c. What are the factors responsible for bringing the ankle into the stable position and what
factors are responsible for maintaining the ankle in its stable configuration?

The factors responsible for bringing the ankle into extension are primarily passive. The
non-reference limb is in swing when the reference limb goes into mid-stance. The forward
movement of the opposite (non-reference limb) drags that side of the torso past the limb
during the process of taking a step. This forces the ankle on the reference side into a
dorsiflexed position. At mid-stance, the ankle is in a dorsiflexed position and stable.
Maintenance of this position involves eccentric contractions of the gastrocnemius and
soleus muscles. These muscles help prevent excessive dorsiflexion of the ankle joint at
this interval.

d. Identify those muscles acting on the ankle during each interval and tell if they are acting
in a concentric or eccentric manner.

See chart on Muscle Actions.

e. What are symptoms would you expect to see if there was a lesion of the common fibular
nerve? What if the tibial nerve were lesioned?

A lesion of the common fibular nerve will result in paralysis of the muscles in the
anterior crural. These muscles include the tibialis anterior, extensor digitorum longus,
extensor hallicus longus and the fibularis tertius muscles. These muscles act to dorsiflex
the ankle joint. In addition, the extensors extend the toes while the tibialis anterior helps
invert the subtalar joint and supinate the tarsal joints. These muscles contract
eccentrically when the reference limb goes into heel strike. Recall that the ankle is in a
neutral position at heel strike. At this interval, the ankle is neutral because gravity wants
to pull the ankle into plantar flexion. This tendency is resisted by the eccentric contraction
of the anterior crural muscles. If these muscles are paralyzed, then gravity wins and the
ankle is pulled into plantar flexion. If this occurs, the patient will have their toes contact
the ground instead of the heel during heel strike. This produces a pronounced "foot slap"
when the foot comes in contact with the ground. This symptom is indicative of a common
fibular nerve lesion.

Problem 4
Your patient comes into your office stating she is experiencing a lot of pain in her back and
leg. She is 45 years old, slightly overweight but in otherwise good health. She states she
started to feel discomfort in her buttock region a few months ago. She took it easy for
awhile and tried to control the pain with asprin. The pain got progressively worse and now
has spread to the back and outside of her left leg and along the outside of her left foot.
Examination reveals a positive response to straight leg raise test. Hip flexion and knee
extension are normal but movements of the ankle and foot seem to be affected. You
perform muscle testing for the following movements: dorsiflexion and plantar flexion of the
ankle, pronation and supination of the tarsal joints. You find plantar flexion and pronation
very weak with dorsiflexion and supination somewhat weak. Hip abduction is also
somewhat weak.

a. Use your Segmental Innervation Chart to determine the site of the disc herniation.

b. What ventral ramus/rami is (are) affected?

The patient in this case has symptoms indicating she may be suffering from "sciatica"
or a herniated disc in the lumbrosacral region of her vertebral column. The pain she is
feeling has progressed from being localized in her gluteal region. Now it is radiating
down to her leg and foot. She also has a positive straight leg raise. Both these signs
indicate herniated disc. In this case, hip flexion and knee extension are unaffected
indicating the herniation does not involve the L1-L3 ventral rami. Muscle testing
indicates plantar flexion and pronation very weak with dorsiflexion and supination some-
what weak. Hip abduction is also somewhat weak. Examining the Segmental Inner-
vation Chart shows that the ankle plantar flexors are innervated by S1 and S2 with S1
being the main ventral ramus supplying these muscles. The fibularis (peroneus) longus
and brevis are the main pronators of the tarsal joints. They are also innervated by the
S1 and S2 ventral rami. Like the plantar flexor muscles, S1 provides the main innerva-
tion to these muscles. Thus, it is likely that the S1 ventral ramus is involved. Examin-
ing the chart on Disc Herniation shows that for S1 to be involved means there is a her-
niation of the disc between the L5 vertebrae and the first sacral vertebrae. Ankle dorsi-
flexion is somewhat weak because the dorsiflexors are primarily innervated by L5.
However, S1 does contribute to their innervation. Thus, this movement is only some-
what affected. The same reason applies to the tarsal joint supinators. These muscles
receive very little input from S1, so they are only slightly affected. The hip abductors,
the gluteus medius and minimus, are primarily L5 muscles. There is some input from
S1 so they are also only slightly affected. The lateral side of the calf and foot are part
of the S1 dermatome. That is why there is pain in these regions.

Problem 5
A 35 year old week-end warrior is playing a game of flag football. He runs out to catch a
pass. He turns to run after making the catch only to hear a loud "pop" in the area of his
knee and he falls down in a lot of pain. He is taken to the emergency room where he is
told he tore all 4 major ligaments of his knee.

a. What caused his ligaments to tear?

This unfortunate individual likely had his foot planted on the ground when he caught the
pass. He turned to run while his feet were both in weight bearing. The force of rotating
(turning) his torso in preparation to run with the football and his foot "locked" to the
ground meant he put a lot of strain on his knee ligaments, tearing them.

b. How would you test for the integrity of both cruciate ligaments and both collateral
ligaments?

To test for the integrity of the anterior cruciate ligament, place the knee in flexion.
Support the thigh with one hand and place the other behind the calf. Keeping the thigh
immobile, see if you can move the tibia forward on the thigh. If you can, the anterior
cruciate ligament is torn. Do the reverse to test for the integrity of the posterior
cruciate ligament. That is, place one hand on the thigh and the other on the dorsum
of the calf. Stabilizing the thigh, try and move the tibia posterior on the thigh. To test
for the integrity of the tibial collateral ligament, keep the knee flexed and place one
hand on the ankle. The other hand is placed on the outside of the thigh. Put a valgus
stress on the knee by moving the ankle outward and pressing inward on the knee.
Excessive movement indicates a problem with the tibial collateral ligament. To test for
the integrity of the fibular collateral ligament, keep the knee flexed and place one
hand on the ankle. The other hand is placed on the inside thigh. Put a varus stress on
the knee by moving the ankle inward while moving the thigh outward. Excessive move
ment indicates a problem with the lateral (fibular) collateral ligament.

c. Which of his menisci is also likely to be torn?

The medial meniscus is likely to be torn because the tibial collateral ligament attaches
to this meniscus. Tears of the tibial collateral ligament often result in tearing of the
medial meniscus.

d. Which tendon that acts as a flexor of the knee could be used to attach to both the tibia
and the femur? This tendon, after surgical attachment, could act like a ligament keeping the
bones of the knee stable upon knee flexion.

Three tendons attach to the anterior medial side of the tibia. These are the pes anserinus
tendons: the tendons of the sartorius, gracilus and semitendinosus muscles. These
muscles help stabilize the medial aspect of the knee, flex and internally rotate the knee
and strengthen the knee capsule. The semitendinosus muscle has a very long tendon.
This tendon can be attached to the lateral femoral condyle via surgery. When the knee
is flexed, this tendon can act as a ligament binding the tibia and femur together, giving the
knee stability.