Download Knee Joint Muscles

Knee Joint Muscles
The knee joint is affected by several muscles, including the quad muscles, hamstrings and
Gastrocnemius. The muscles on this page are those that surround the front of the knee cap and
affect the functioning of the patellofemoral joint. Also included is the popliteus, which unlike other
mucles around the knee, functions only on the knee.
Click the pictures below for more information on muscle attachments, actions and nerve supplies.
Vastus lateralis
The most lateral of the quadricep muscles.
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Vastus intermedius
A deep, central quad muscle.
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Vastus medialis
The most medial of the quadricep muscles.
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Popliteus
A small muscle at the back of the knee joint.
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The four quadricep muscles act to extend (straighten) the knee joint. They are also important in
the movement of the knee cap. All four quad muscles converge at the top of the patella into one
tendon - the patella tendon - which attaches to the top of the shin bone. The patella is a
sesamoid bone which means it is encased within the tendon and slides up and down in it's grove
at the front of the knee. Commonly, the vastus lateral muscle is stronger and tighter than the
vastus medialis (specifically the VMO portion). This can result in mal-tracking of the knee cap, as
occurs in patellofemoral pain syndrome.
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Vastus Lateralis
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Vastus Lateralis is the most lateral (outer) of the four quadriceps muscles and is
felt on the outside top of the thigh.
Origin
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Outer surface of the greater trochanter of the femur.
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Upper half of the linea aspera.
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon.
Actions

Knee extension.
Innervation

Femoral nerve.
Daily uses
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Cycling.
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Walking up stairs.
Example strengthening exercises

Knee extension.

Squats.
Example stretches

Standing quad stretch.

Laying quad stretch.
Related injuries

Quad strain

Contusion.
Related muscles
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Vastus medialis.
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Vastus intermedius.

Rectus femoris.
Vastus Intermedius
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Vastus Intermedius is one of four quadricep muscles, located deep in the thigh
underneath the Rectus Femoris muscle.
Origin
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Anterior and lateral surfaces of the shaft of the femur.
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon.
Actions

Knee extension.
Innervation

Femoral nerve.
Daily uses

Cycling.

Walking up stairs.
Example exercises

Knee extension with a band.

Squats.
Example stretches

Standing quadriceps stretch.

Laying quadricep stretch.
Related injuries

Quad strain.

Contusion.
Related muscles

Vastus medialis.

Vastus lateralis.

Rectus femoris.
Vastus Medialis
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Vastus Medialis is the most medially (inner) located of the quadricep muscles.
The portion of the muscle just above the knee is known as VMO (vastus medialis
oblique). This is important in stabilising the knee joint and often becomes
inhibited following injury.
Origin

Intertrochanteric line (between the greater and lesser trochanters of the femur).

Medial lip of the linea aspera of the femur.
Insertion

Patella via the quadriceps tendon and then the tibial tuberosity via the patella tendon.
Actions

Knee extension.
Innervation

Femoral nerve.
Daily uses

Cycling.

Walking up stairs.
Example strengthening exercises

Knee extension with a rehab band.

Squats.
Example stretches

Standing quad stretch.

Laying quad stretch.
Related injuries

Quad strain.

Contusion.
Related muscles

Vastus lateralis.

Vastus intermedius.

Rectus femoris.
Popliteus
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Popliteus is a small muscle which is often described as the key of the knee joint.
It unlocks the knee joint by rotating the femur at the beginning of knee flexion to
allow full knee flexion to occur.
Origin

Lateral condyle of the femur.
Insertion

Upper posterior surface of the tibia, above the soleal (popliteal) line.
Actions

Knee flexion.

Internal rotation of the knee when it is flexed.
Innervation

Tibial nerve.
Daily uses

Walking.
Related injuries

Popliteus injury.
Related muscles

Biceps femoris.

Semimembranosus.
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Semitendinosus