Knee Muscular Anatomy

Knee Flexors

Semitendinosus Origin Insertion Action Nerve Supply Palpation Lower medial facet of the lateral section of the ischial tuberosity Insertion Vertical line of the anterior medial superior aspect of the medial condyle of the tibia Action Hip Extension, Knee Flexion and Tibial Internal Rotation Nerve Supply Tibial Division of Sciatic Nerve 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.

Semimembranosus Origin Insertion Action Nerve Supply Palpation Upper lateral facet of the ischial tuberosity Insertion Posteromedial surface of the medial tibial condyle and oblique popliteal ligament Action Hip Extension, Knee Flexion and Tibial Internal Rotation Nerve Supply Tibial Division of Sciatic Nerve 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 Insertion Action Nerve Supply Palpation 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 Insertion Head of the fibula Action Hip Extension, Knee flexion and Tibial External Rotation Nerve Supply Long Head: Tibial Division of Sciatic Nerve 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. Biceps Femoris

Gastrocnemius Origin Insertion Action Nerve Supply Palpation 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 Insertion Action Nerve Supply Palpation 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 Palpation Distal Tendon: Resist knee flexion and tibial IR. Tendon is medial to the tendon of semitendinosis 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. Gracilis

Anterior superior iliac spine and area just below 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 Insertion Action Nerve Supply Palpation Fascia from gluteus maximus and tensor fascia latae Insertion Lateral femoral epicondyle and Gerdy’s tubercle of the anterolateral aspect of the tibia Action Assists with knee flexion atAssists with knee flexion at angles greater than 30° Assists with knee extension at angles smaller than 30° angles greater than 30° Nerve Supply N/A Palpation

Popliteus Origin Insertion Action Nerve Supply Palpation 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 Origin Insertion Action Nerve Supply Palpation Straight Head: Anterior inferior iliac spine Insertion Upper border of the patella and merges around patella to form parts of the ligamentum patellae Action Hip flexion, Knee Extension Nerve Supply Femoral Nerve Palpation Model: Straight leg raise 

Tendon of rectus femoris and lateral border of the patella 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 Lateralis

Vastus Medialis Origin Insertion Action Nerve Supply Palpation 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 Medialis

Vastus Intermedius Origin Insertion Action Nerve Supply Palpation 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 Vastus Intermedius

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