Biomechanics

GACHON UNVERSITY Dept, of Physical Therapy

Choi Won Ho

Chapter 12

Knee

Anatomic Considerations

The quadriceps femoris is a large and powerful extensor muscle, consisting of the rectus femoris, vastus lateralis, vastus medialis, and deeper vastus intermedius.

Contraction of the vasti extends the knee only.

Contraction of the rectus femoris, however, causes hip flexion and knee extension.

The vastus lateralis and vastus medialis attach into the capsule and menisci via patellar retinacular fibers.

The quadriceps muscle and tendon, patella, and patellar ligament are often described as the knee extensor mechanism.

Anatomic Considerations

The rectus femoris attaches to the pelvis near the anterior-

inferior iliac spine. The vastus muscles, however, attach to an extensive part of

the femur, particularly the anterior-lateral shaft and the linea aspera.

Although the vastus lateralis is the largest of the quadriceps muscles, the vastus medialis extends farther distally toward the knee.

Vastus intermedius contains a few slips of muscle fibers that attach proximally to the anterior side of the distal femur, and distally into the anterior capsule.

This muscle pulls the capsule and synovial membrane proximally during active knee extension.

Functional Considerations

By isometric, eccentric, and concentric activations, the

quadriceps femoris muscle is able to perform multiple functions at the knee.

Through isometric activation, the quadriceps stabilizes and helps to protect the knee; through eccentric activation, the quadriceps controls the rate of descent of the body’s center of mass, such as in sitting or stooping.

Eccentric activation provides shock absorption to the knee. At the heel contact phase of walking, the knee flexes slightly

in response to the posteriorly located ground reaction force.

Functional Considerations

Eccentrically active quadriceps controls flexion. Acting as a spring, the muscle helps dampen the impact of

loading on the joint.

This protection is especially useful during high impact loading, such as landing from a jump, running, of descending from a high step.

A person whose knee is braced or fused in full extension lacks this natural shock absorption mechanism.

Functional Considerations

In the previous examples, eccentric activation of the

quadriceps is employed to decelerate knee flexion.

Concentric contraction of this muscle, in contrast, accelerates the tibia or femur into knee extension.

This action is often used to raise the body’s center of mass,

such as running uphill, jumping, or standing from a seated position.

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External torque demands against the quadriceps

Internal torque-joint angle relationship of the quadriceps muscle

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Consequences of a patellectomy

Consequences of a patellectomy

시상면에서의 가동범위동안 무릎 폄 모멘트 팔의 길이에 영향을 미치는 3가지 요소

1.무릎뼈의 형태와 위치

2.먼쪽 넙다리뼈의 형태

3.무릎에서 안-가쪽 돌림축의 이동

*근육길이와 지레작용은 가동범위 내내 변하고, 이 두 인자는 직접 또는 간접적으로 무릎 폄 토크에 영향을 미친다.

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Patellofemoral joint kinetics

무릎넙다리관절의 압박력

•평지를 걷는동안- 체중의 1.3배

•뻗은발올림-체중의 2.6배

•계단보행-체중의 3.3배

•깊게 무릅을 구부리는 동작-체중의 7.8배

무릎넙다리관절에 가해지는 관절의 압박력과 관계된 2가지 인자

1.네갈래근에서의 힘

2.무릎의 굽힘각도

“무릎넙다리통증 증후군(patellofemoral pain syndrome)”

비정상적인 무릎뼈의 “이동경로(tracking)”

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Patellofemoral joint kinetics

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