THE KNEE JOINT Muscles That Act On The Knee

Muscles of the Knee Joint  Hamstrings All - flexion  Quadriceps All - extension  Unclassified Sartorius - flexion and internal rotation Gracilis - flexion and internal rotation Popliteus - flexion (unlocking) and internal rotation Gastrocnemius - flexion

Anterior Muscles  Quadriceps knee extension

Vastus medialis  Origin: Medial lip of the linea aspera  Insertion: Inner half of the quadriceps tendon then the tibial tuberosity via the patellar tendon  Action: Extension of the knee

Rectus femoris  Two joint muscle; most superficial  Origin: anterior-inferior iliac spine of the ilium  Insertion: top of the patella and patellar ligament to the tibial tuberosity  Actions: Extension of the knee

Vastus lateralis  Origin: Lateral lip of linea aspera.  Insertion: The lateral quadriceps tendon then the tibial tuberosity via the patellar tendon  Action: Extension of the knee

Vastus intermedius  Origin: Upper 2/3 of the anterior surface of the femur  Insertion: Upper border of the quadriceps tendon then the tibial tuberosity via the patellar tendon  Action: Extension of the knee

Quadriceps Muscles

VLRFVM

Quadriceps Hamstrings Vastus Lateralis Vastus Intermedius Rectus Femoris Vastus Medialis

QUADRICEPS MUSCLES  Vertical jumping  Decelerating or eccentric contraction during landing or changing directions  As a group, they are typically 25-30% stronger than the hamstrings

Posterior Knee Muscles

Hamstrings  knee flexion

Biceps femoris  Lateral side  Origin: 1.) Long head - ischial tuberosity; 2.) Short head - lower half of the linea aspera  Insertion: Head of the fibula  Action: Flexion of knee

Semitendinosus  Medial side; superficial  Origin: Ischial tuberosity  Insertion: Anterior medial surface of the tibia  Action: Flexion of the knee

Semimembranosus  Medial side, deeper than semitendonosus  Origin: Ischial tuberosity  Insertion: Anterior medial surface of the tibia  Action: Flexion of the knee

HAMSTRING MUSCLES  More “knee flexors” than “hip extenders”  Acceleration muscles during running  Tight hamstring muscles can contribute to lower back, hip and knee problems

Gracilis  O: Pubis crest  I: Anterior medial surface of the (Pes anserine Tendon)  Actions: flexion at the knee

Sartorius  Posterior at the knee joint  Origin: Anterior-superior spine of the ilium  Insertion: Anterior medial surface of the tibia (Pes anserine Tendon)  Action: Flexion at the knee Internal Rotation Abduction of Hip (hackey sack)

Popliteus  Origin: Lateral condyle of the femur  Insertion: Proximal medial tibia  Action: Flexion of the knee It "unlocks" the knee.

Gastrocnemius  Origin: medial and lateral femoral condyles  Insertion: the calcaneus through the Achilles tendon  Actions: Flexion of the knee Posterior

Review  Superficial Leg Muscles Superficial Leg Muscles  GET OUT YOUR THREE PACKETS  TEST NEXT CLASS

Sartorius Action: Flexion at the knee Name the muscle and its action(s)

Terms  Valgus  Varus  Stress to lateral side of the knee  Stress to the medial side of the knee

Semimembranosus  Action: Flexion of the knee Name the muscle and its action(s)

1. Anterior cruciate ligament 2. Lateral collateral ligament 3. Lateral meniscus 4. Posterior cruciate ligament 5. Medial collateral ligament 6. Medial meniscus

Semitendinosus  Action: Flexion of the knee Name the muscle and its action(s)

= PCL 2 = Lateral meniscus 3 = ACL 4 = Medial meniscus

2 = Vastus lateralis 1 = Rectus femoris 4 = Vastus medialis Name the colored muscles

Femur ? = Lateral condyle Medial condyle Intercondylar fossa

Gracilis Action - flexion at the knee Name the muscle and its action(s)

Tibia Medial condyle Lateral condyle Medial Malleolus? = ? =

= Vastus lateralis 2.= Rectus femoris 3.= Vastus medialis

VLRFVM

Rectus femoris  Actions: Extension of the knee Name the muscle and its action(s)

= Anterior cruciate ligament 2. = Lateral collateral 3. = Lateral meniscus 3. = Medial collateral 4. = Medial mieniscus

Fibula Head Lateral malleolus ? =

 Biceps femoris  Biceps femoris  Semitendonosis  Semimembranosis Name the muscles

Biceps femoris  Action: Flexion of knee Name the muscle and its action(s)

Tibia Medial condyle Lateral condyle Medial Malleolus ? =

Popliteus  Action: Flexion of the knee Name the muscle and its action(s)

Femur 6 = ? 7 = ? 8 = ? Lateral condyle Intercondylar fossa Medial condyle