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Knee Muscular Anatomy
Knee Flexors
Semitendinosus
Origin
Insertion
Action
Lower medial facet of the lateral section of
the ischial tuberosity
Vertical line of the anterior medial superior
aspect of the medial condyle of the tibia
Hip Extension, Knee Flexion and Tibial
Internal Rotation
Tibial Division of Sciatic Nerve
Nerve Supply
Palpation
Patient in prone with the leg partially flexed
at the knee joint. Place palpating hand on
the posteromedial thigh and resist flexion of
the leg at the knee joint and feel for the
distal tendon of the semitendinosus.
Continue palpating the muscle proximally
toward the ischial tuberosity.
Upper lateral facet of the ischial tuberosity
Semimembranosus
Origin
Insertion
Action
Posteromedial surface of the medial tibial
condyle and oblique popliteal ligament
Hip Extension, Knee Flexion and Tibial
Internal Rotation
Tibial Division of Sciatic Nerve
Nerve Supply
Palpation
Best palpated distally in the posterior thigh,
medial to the belly of the semitendinosus,
and on either side of the distal tendon of
the semitendinosus. Patient in prone with
the leg partially flexed at the knee joint.
Palpating hand on the distal posteromedial
thigh. Resist knee flexion and feel for
contraction of the semimembranosus.
Biceps Femoris
Origin
Long Head: Lower medial facet of the
ischial tuberosity and sacrotuberous
ligament
Short Head: Lower half of the lateral lip of
the linea aspera and the lateral
supracondylar line of the femur
Head of the fibula
Insertion
Action
Hip Extension, Knee flexion and Tibial
External Rotation
Long Head: Tibial Division of Sciatic Nerve
Nerve Supply
Palpation
Patient in prone with the leg partially flexed
at the knee joint. Place palpating hand on
the distal posterolateral thigh, resist knee
flexion and feel for the distal tendon of the
biceps femoris. Continue palpating the
biceps femoris toward the ischial tuberosity.
Gastrocnemius
Origin
Medial supracondylar ridge and adductor
tubercle of the medial femur. Lateral
condyle femur. Posterior capsule of the knee
from oblique popliteal ligament
Insertion
Middle Part of the posterior surface of the
calcaneus
Action
Ankle Plantarflexion, Knee Flexion
Nerve Supply
Tibial Nerve
Palpation
Patient in prone with the leg extended at
the knee joint. Place palpating hand on the
proximal posterior leg and ask the patient
to actively plantarflex the foot at the ankle
joint against resistance and feel for
contraction of the muscle. Palpatedall the
way to its distal attachment
Gracilis
Origin
Front body and inferior ramus of the pubis
and the ramus of the ischium
Insertion
Vertical line of the upper medial surface of
the tibia shaft
Action
Hip adduction. Knee Flexion and Tibial
Internal Rotation
Nerve Supply
Anterior division of the obturator nerve
Distal Tendon: Resist knee flexion and tibial
IR. Tendon is medial to the tendon of
semitendinosis
Palpation
Proximal belly: Place thigh into hip flexion,
abduction, ER. Place flat palm along
adductors. Immediate muscle mass is
adductor longus. Straighten knee. Mass
then found posteriorly is gracilis.
Sartorius
Origin
Anterior superior iliac spine and area just
below
Insertion
Vertical line of the upper medial surface of
the tibia shaft. Some fibres merge with the
MCL
Action
Hip flexion, external rotation and abduction.
Knee flexion and tibial internal rotation.
Nerve Supply
Femoral Nerve
Palpation
Model actively holds leg in hip flexion,
abduction and slight external rotation. Belly
palpated close to ASIS
ITB
Origin
Fascia from gluteus maximus and tensor
fascia latae
Insertion
Lateral femoral epicondyle and Gerdy’s
tubercle of the anterolateral aspect of the
tibia
Assists with knee flexion atAssists with
knee flexion at angles greater than 30°
Action
Assists with knee extension at angles
smaller than 30°
angles greater than 30°
Nerve Supply
Palpation
N/A
Popliteus
Origin
Posterior aspect of the lateral condyle of the
femur
Insertion
Triangular area on the posterior surface of
the tibia
Action
Lateral rotation of the femur on tibia in
weight bearing. Medial Rotation of tibia on
femurs in non-weight bearing. Knee flexion
Nerve Supply
Tibial Division of the Sciatic Nerve
Palpation
Tendon: Posterior to LCL and superior to the
joint line. Gently resist knee flexion
Knee Extensors
Rectus Femoris
Straight Head: Anterior inferior iliac spine
Origin
Insertion
Upper border of the patella and merges
around patella to form parts of the
ligamentum patellae
Hip flexion, Knee Extension
Action
Femoral Nerve
Nerve Supply
Model: Straight leg raise
Palpation
Vastus Lateralis
Origin
Upper lateral part of the Intertrochanteric
line, lower border of the greater trochanter,
the lateral side of the gluteal tuberosity and
upper half of the linea aspera. Also merges
with the ITB
Insertion
Tendon of rectus femoris and lateral border
of the patella
Action
Knee Extension
Nerve Supply
Femoral Nerve
Palpation
Patient is supine. Place palpating hand just
distal to the greater trochanter and ask the
patient to contract the quadriceps femoris
group. Feel for contraction of the vastus
lateralis and continue palpating distally
toward the patella
Vastus Medialis
Origin
Lower medial end of the intertrochanteric
line, medial aspect of the upper end of the
shaft on the spiral line, medial lip of the
linea aspera, upper 2/3 of the medial
supracondylar line and medial intermuscular
septum
Insertion
Tendon of rectus femoris and medial border
of the patella, the anterior medial condyle
of the tibia, and the tibial tuberosity
Action
Knee Extension
Nerve Supply
Femoral Nerve
Palpation
Patient in supine. Place palpating hand just
proximal and medial to the patella. Ask the
client to contract the quadriceps femoris
group and feel for the contraction of the
vastus medialis. The vastus medialis is best
palpated medially in the distal 1/3 of the
thigh
Vastus Intermedius
Origin
Upper 2/3 of the anterior and lateral surface
of the femur
Insertion
Deep surface of the rectus femoris tendon
and the base of the patella
Action
Knee Extension
Nerve Supply
Femoral Nerve
Palpation
Deep and difficult to palpate. Patient in
supine. Place palpating hand just proximal
to the patella. Rectus femoris can be lifted
and/or moved aside, the distal vastus
intermedius may be palpated deep to the
rectus femoris when approached from
either the medial or lateral side. The
direction of your pressure is directed toward
the middle of the femur
Flexion
Semitendinosus
Semimembranosus
Biceps Femoris
Gastrocnemius
Gracilis
Sartorius
ITB (> 30° Flexion)
Popliteus
Extension
Rectus Femoris
Vastus Lateralis
Vastus Medialis
Vastus Intermedius
ITB ( < 30° Flexion)
Tibial External
Rotation
Biceps Femoris
ITB
Tibial Internal
Rotation
Popliteus (Open Chain)
Semitendinosus
Semimembranosus
Gracilis
Sartorius