The Knee Complex - Muscles & Tendons

3. Muscles and tendons (6-minutes): Identification and palpation of key muscles and tendons, demonstration of their actions, and explanation of relevant origins and insertions. You may be asked to demonstrate basic muscle testing where appropriate. Follow-up questions may explore contraction type and structure/function. "Tell me what you know about the muscles acting at the knee complex."

How many Knee Extensor muscles are there?

Four

How many Knee Flexor muscles are there?

Six

Name the four Knee Extensor muscles.

1. Vastus Lateralis

2. Vastus Medialis

3. Vastus Intermedialis

4. Rectus Femoris

What is the origin of Vastus Lateralis?

The Greater Trochanter

What is the insertion of Vastus Lateralis?

The Tibial Tuberosity (via the Patella Tendon)

What is the action of Vastus Lateralis?

Tibiofemoral Extension (the Sagittal plane)

What is the antagonist of Vastus Lateralis?

The knee flexors

What is the nerve supply of Vastus Lateralis?

The Femoral nerve

What is the origin of Vastus Medialis?

Proximal Anteromedial Femur

What is the insertion of Vastus Medialis?

The Tibial Tuberosity (via the Patella Tendon)

What is the action of Vastus Medialis?

Tibiofemoral Extension (the Sagittal plane)

Most active in the final 30^o of extension

What is the antagonist of Vastus Medialis?

The knee flexors

What is the nerve supply of Vastus Medialis?

The Femoral nerve

What is the origin of Vastus Intermedialis?

Proximal Anteromedial Femur

What is the insertion of Vastus Intermedialis?

The Tibial Tuberosity (via the Patella Tendon)

What is the action of Vastus Intermedialis?

Tibiofemoral Extension (the Sagittal plane)

What is the antagonist of Vastus Intermedialis?

The knee flexors

What is the nerve supply of Vastus Intermedialis?

The Femoral nerve

What is the origin of Rectus Femoris?

Anterior Inferior Iliac Spine (AIIS)

What is the insertion of Rectus Femoris?

The Tibial Tuberosity (via the Patella Tendon)

What is the action of Rectus Femoris?

Tibiofemoral Extension (the Sagittal plane)

Femoroacetabular Flexion (the Sagittal plane)

What is the antagonist of Rectus Femoris?

The knee flexors and hip extensors

What is the nerve supply of Rectus Femoris?

The Femoral nerve

Name the six Knee Flexor muscles.

1. Semitendinosus

2. Semimembranosus

3. Biceps Femoris Long Head

4. Biceps Femoris Short Head

5. Popliteus

6. Gastrocnemius (Medial and Lateral Belly)

What is the origin of Semitendinosus?

Ischial Tuberosity

What is the insertion of Semitendinosus?

Pes Anserine

What is the action of Semitendinosus?

Tibiofemoral Flexion (the Sagittal plane)

Femoroacetabular Extension (the Sagittal plane)

What is the antagonist of Semitendinosus?

The knee extensors and hip flexors

What is the nerve supply of Semitendinosus?

The Sciatic nerve

What is the origin of Semimembranosus?

Ischial Tuberosity

What is the insertion of Semimembranosus?

Medial Condyle of the Tibia

What is the action of Semimembranosus?

Tibiofemoral Flexion (the Sagittal plane)

Femoroacetabular Extension (the Sagittal plane)

What is the antagonist of Semimembranosus?

The knee extensors and hip flexors

What is the nerve supply of Semimembranosus?

The Sciatic nerve

What is the origin of Biceps Femoris Long Head?

Ischial Tuberosity

What is the insertion of Biceps Femoris Long Head?

Head of Fibula

What is the action of Biceps Femoris Long Head?

Tibiofemoral Flexion (the Sagittal plane)

Femoroacetabular Extension (the Sagittal plane)

What is the antagonist of Biceps Femoris Long Head?

The knee extensors and hip flexors

What is the nerve supply of Biceps Femoris Long Head?

The Sciatic nerve

What is the origin of Biceps Femoris Short Head?

Linea Aspera

What is the insertion of Biceps Femoris Short Head?

Head of Fibula

What is the action of Biceps Femoris Short Head?

Tibiofemoral Flexion (the Sagittal plane)

What is the antagonist of Biceps Femoris Short Head?

The knee extensors

What is the nerve supply of Biceps Femoris Short Head?

The Sciatic nerve

What is the origin of Popliteus?

Lateral Femoral Condyle

What is the insertion of Popliteus?

Proximal Posterior Tibia

What is the action of Popliteus?

Tibiofemoral Flexion (the Sagittal plane)

Helps to initiate flexion from a locked knee

What is the antagonist of Popliteus?

The knee extensors

What is the nerve supply of Popliteus?

The Tibial nerve

What is the origin of the Medial Belly of Gastrocnemius?

Medial Femoral Condyle

What is the origin of the Lateral Belly of Gastrocnemius?

Lateral Femoral Condyle

What is the insertion of Gastrocnemius?

The Calcaneus (via the Achilles Tendon)

What is the action of Gastrocnemius?

Tibiofemoral Flexion (the Sagittal plane)

Talocrural Plantarflexion (the Sagittal plane)

What is the antagonist of Gastrocnemius?

What is the nerve supply of Gastrocnemius?

The Tibial nerve