Kinesiology Lab: Lower Extremity Mechanics

A diarthrosis joint, specifically planar, allowing gliding motions.

One degree of freedom (DF-PF), meaning primarily dorsiflexion (DF) then plantarflexion (PF).

Allows inversion and eversion. Doesn't have major active range of motion (ROM).

Maximum dorsiflexion (DF)

Contributes to pronation and supination during walking with inversion and eversion.

4-6 degrees of inversion (INV) and eversion (EV) during walking, resulting in a total range of 9-12 degrees.

A firm end-feel during inversion due to tension in the lateral collateral ligament, evertors talocalcaneal ligaments, and lateral joint capsule.

A firm/hard end-feel during eversion due to contact between the talus and calcaneus, plus tension in medial structures.

Inversion (INV) has greater limitation than eversion (EV) in the subtalar joint.

Supination (combination of talocrural DF, subtalar INV/ADD, and foot adduction).

Pronation (combination of talocrural DF, subtalar EV/ABD, and foot abduction).

Slight supination with lower extremity in external rotation (ER) during heel strike in gait.

Increasing supination and external rotation (hip and knee locking) during push-off phase of gait.

The perpendicular distance between the line of action of a force and the axis of rotation.

The force of gravity acting on the body's mass, creating a rotational effect around a joint.

The HAT's weight creates an adduction moment around the weightbearing hip, tending to drop the pelvis on the opposite side.

Hip abductor muscles counteract the adduction moment of the HAT, stabilizing the pelvis and preventing it from dropping on the unsupported side.

The force exerted by the hip abductor muscles and the weight of the body, acting on the femoral head during unilateral stance.

A walking pattern where the trunk leans over the painful hip during single leg stance, reducing the load on the injured joint.

Antalgic gait reduces the adduction moment on the painful hip by shifting the body's weight more directly over the joint, relieving stress.

By reducing the adduction moment and the compression force on the painful hip, antalgic gait minimizes pain and allows for easier movement.

A gait characterized by a drop of the pelvis on the side opposite the weak hip abductor muscles, typically caused by weakness or damage to the gluteus medius.

When using a cane for pain relief in hip problems, the cane should be held on the side opposite the affected hip. This reduces stress on the painful joint and improves balance.

Changing the angle of inclination (coxa valga or vara) impacts hip abductor muscle efficiency. Coxa valga increases the moment arm, making abduction easier, while coxa vara reduces the moment arm, requiring more effort.

In hip replacements, placing the femoral neck in coxa vara (smaller angle) can be beneficial by reducing stress on the femoral head and potentially improving stability.

Weakness in hip abductors can lead to increased activation of the quadratus lumborum on the opposite side, potentially causing muscle shortening and tightness.

In relaxed standing, weight is distributed equally between the medial and lateral condyles of the knee. During dynamic activities, the mechanical axis shifts medially, increasing medial compressive forces.

The MCL's tension during knee valgus movement generates a laterally directed component of the joint reaction force, helping stabilize the joint.

The tibiofemoral joint has a limited arc of motion on its medial compartment due to the strong restraint of the axis of rotation.

Due to the medial shift of the mechanical axis during dynamic activities, the medial side of the knee experiences higher compressive forces. This can contribute to osteoarthritis if not managed properly.

During weight-bearing, concentric soleus contraction causes posterior tibial translation, which helps stabilize the ACL.

In weight-bearing, concentric hamstring contraction causes posterior tibial translation, further assisting ACL stability, especially during greater knee flexion.

During weight-bearing, concentric gastrocnemius contraction results in anterior tibial translation or posterior femoral translation, aiding PCL stability.

An isolated quadriceps concentric contraction in full knee extension creates anterior tibial translation, putting increased strain on the ACL.

Co-activation of hamstrings and quadriceps during knee flexion, particularly ≥60°, helps reduce ACL strain by countering the anterior tibial translation caused by the quadriceps.

The patella increases the mechanical advantage of the quadriceps muscle during knee extension.

The quadriceps generates its maximum force, or moment, between 45-60° of knee flexion.

The patella is most functionally significant at 15° of flexion (near full extension) where the quadriceps' ability to generate a moment of force on the tibia is minimal.

A condition where the patella sits higher than normal on the femur, increasing the distance between the patella and the femoral groove. This alters the mechanics of the patellofemoral joint, affecting the forces and movements during knee flexion and extension.

A condition where the patella sits lower than normal on the femur, decreasing the distance between the patella and the femoral groove. This alters the mechanics of the patellofemoral joint, affecting the forces and movements during knee flexion and extension.

The angle formed between the quadriceps muscle and the patellar tendon, indicating the alignment of the femur and tibia. A normal Q-angle is 10-15 degrees. Deviation from this range can affect patellofemoral joint mechanics and increase stress on the patella.

The Vastus Lateralis (VL) and Vastus Medialis (VM) muscles contribute to knee extension and also exert a posterior force that increases the compressive force on the patellofemoral joint, even during knee extension.

The axis of rotation of the talocrural joint (ankle) is not a straight line but is slanted at 14° in the transverse plane and 23° in the frontal plane. This oblique axis allows for coupled motions in all three planes of motion during ankle movements.

During dorsiflexion (DF) of the ankle, the talus moves slightly laterally (abduction) and the foot everts (medial tilt).

During plantarflexion (PF) of the ankle, the talus moves slightly medially (adduction) and the foot inverts (lateral tilt).

During dorsiflexion (DF) in a closed kinetic chain (CKC), the tibia rotates medially on the talus.