Gait Flashcards
As indicated in Figure 12-12, during the swing phase of walking the hip experiences (compression) forces of about 10–20% of body weight. What causes this force?
During the swing phase of walking, the forces from the contracting hip flexor muscles compress
Justify how bilateral tightness in the adductor longus and brevis could contribute to excessive lumbar lordosis while standing.
Because the adductor longus and adductor brevis are also hip flexors, their bilateral tightness may be expressed as an exaggerated anterior pelvic tilt, at least while standing. An increased anterior pelvic tilt is associated with an increased lumbar lordosis.
ad of the femur against the acetabulum.
Explain why the patellofemoral joint is least mechanically stable in the last 20 to 30 degrees of knee extension.
At the last 20–30 degrees of full knee extension, the patella is less stable and more susceptible to lateral dislocation because (a) it is less physically engaged within the trochlear groove of the femur, (b) the Q-angle is greatest owing to the external rotation component of the screw-home mechanism, and (c) the compression forces due to quadriceps contraction are relatively low at the patellofemoral joint.
. Why do most persons have slightly greater active knee flexion range of motion with the hip fully flexed as compared to fully extended?
First, performing active (or passive) knee flexion from a position of full hip extension creates increased passive tension in the elongated rectus femoris. This increased passive tension naturally opposes knee flexion. Second, performing active knee flexion with the hip in full extension requires that the hamstrings function at an overly shortened length. The shortened length reduces the muscle’s ability to actively flex the knee, especially against the increased passive tension generated by the stretched rectus femoris.
What is the primary mechanism by which the menisci reduce pressure across the articular surfaces of the knee?
The menisci reduce pressure across the articular surfaces of the knee by increasing the fit and contact area between the tibia and femur. This protective function requires that the menisci are securely attached to the intercondylar area of the tibia.
Which of the following activities create greater compression stress (pressure) on the articular surfaces of the patellofemoral joint: (a) maintain holding a partial squat with knees flexed to 10–20 degrees or (b) holding a deeper squat with knees flexed to 60–90 degrees? Why?
Holding a deeper squat creates greater joint compression stress on the patellofemoral joint because of the increased force demands placed on the quadriceps in conjunction with the reduced knee joint angle. As shown in Figure 13-28B, the greater knee flexion increases the sum of the quadriceps and patellar tendon forces that oppose the patellofemoral joint.
Which structures (joints and connective tissues) bind the fibula to the tibia?
The fibula and tibia are bounded by the interosseous membrane and ligament, the anterior tibiofibular ligament, and the posterior tibiofibular ligament.
Describe the roll-and-slide arthrokinematics of dorsiflexion at the talocrural joint with the foot free (Figure 14-18A) and with the foot fixed (Figure 14-2
With the foot free, dorsiflexion occurs by an anterior roll and posterior slide of the talus. (To help visualize the rolling of the talus, it may be helpful to follow the rotation of an imaginary point on the inferior aspect of the bone rather than on its superior [trochlear] surface.) With the foot fixed, dorsiflexion occurs by an anterior roll and anterior slide of the tibia and fibula (concave segment of the mortise) relative to the talus.
Which part of the gait cycle requires greater dorsiflexion at the talocrural joint: the stance phase or the swing phase?
Dorsiflexion of the ankle is greatest during the stance phase, at about 40% of the gait cycle (Figure 14-19). This maximal range of dorsiflexion occurs just before the initiation of the push off phase of the gait cycle.
Why do the medial collateral ligament and the medial meniscus often become traumatized by a similar mechanism of injury?
The deeper fibers of the medial collateral ligament attach partially to the medial meniscus. Excessive tension applied to this ligament during an excessive and combined valgus and axial rotation stress to the knee, for example, may be transferred to the medial meniscus, possibly creating injury.
. Describe how contraction of the quadriceps muscle could elongate (strain) the anterior cruciate ligament. How is the strain on the ligament affected by (a) the knee joint angle and (b) the magnitude of quadriceps and hamstring muscle coactivation?
An isolated contraction of the quadriceps can create an anterior force on the proximal tibia that elongates and therefore increases the tension and length in the ACL. In general, the tension in the ACL is proportional to the contractile force in the quadriceps. The magnitude of the muscular-based tension in the ACL increases as the knee moves closer to full extension because the quadriceps produces a greater anterior translation force on the tibia (based on the increased angle of insertion of the patellar tendon onto the tibia). Because of the unloading effect of hamstring activation on the ACL, coactivation of the quadriceps and hamstring muscles reduces the tension on the ACL, bringing it close to zero at knee angles greater than 30 degrees of flexion.
Describe the timing and type of muscular activity of the quadriceps muscle during the early part of the stance phase of gait.
During the early part of the stance phase of gait, the quadriceps are active eccentrically to control the slight flexion of the knee. This muscular action helps absorb the impact of the lower limb striking the ground.
Gait cycle:
Starts at _____ ______ (heel strike)
100% complete when same _____ starts again
heel contact
foot
_________ = events taking place between heel contacts of same foot (length is the distance)
stride
_______ = events taking place between heel contacts of opposite feet (length is the distance)
step
_______ _______ = lateral distance between heel centers of 2 successive heel contacts – avg 8-10 cm
step width
_______ _________ or “_____ ______ __________ ________” = line of progression and long axis of foot (5-7 degrees)
foot angle
toe out progression angle
__________ = # of steps per minute (step rate)
cadence
____ _______ = the time for a full gait cycle
stride time
______ ______ the time for completion of a step
step time
_________ ________ distance covered in a given time usually in meters per second m/s or mph. Speed may be one of the best functional measure of walking ability.
walking speed
A healthy adult gait cycle ( ____ steps) = ____ feet in > ____ sec or _____m/sec
2
4.5
1
1.37
Women have a slower ______ but shorter _____ _____ with faster cadence
speed
step length
_______ phase: R toe off until R heel contact 40%
Swing
