Overview
This lecture covers the major muscles controlling the hip and knee joints, focusing on their origin, insertion, actions, and identification strategies.
Movements and Joints Clarification
- Movements are named for the joint being acted upon, not just the moving limb (e.g., flexing the hip joint moves the entire lower limb).
- Hip joint movement involves the thigh or lower limb, whereas knee joint movement is distinct.
Muscles of the Hip Joint
- Gluteus maximus: originates from sacrum and iliac crest, inserts on gluteal tuberosity; largest gluteal muscle.
- Gluteus medius: originates from iliac crest, inserts on greater trochanter; responsible for hip abduction.
- Piriformis: originates from sacrum, inserts on greater trochanter.
- Quadratus femoris: identifiable, but specific action/origin/insertion not required for this course.
- Tensor fasciae latae: tenses the iliotibial band (IT band), which supports leg movement.
- Iliacus: originates from iliac fossa, inserts on lesser trochanter, flexes hip.
- Psoas major: originates from lumbar vertebrae, inserts on lesser trochanter, merges with iliacus to form iliopsoas, also flexes hip.
- Gracilis and adductor magnus: originate from inferior pubic ramus, insert on medial condyle of tibia (gracilis) and linea aspera (adductor magnus), both adduct the hip.
- Adductor longus: long adductor muscle in the inner thigh.
Muscles of the Knee Joint
- Sartorius: originates at anterior superior iliac spine, inserts on tibial tuberosity; flexes hip, flexes knee, and laterally rotates hip.
- Quadriceps femoris: includes rectus femoris (origin: anterior inferior iliac spine), vastus medialis (origin: linea aspera), vastus lateralis, and vastus intermedius (origins: femur); all insert on tibial tuberosity; rectus femoris flexes hip and extends knee, others extend knee.
- Hamstrings: include biceps femoris (long/short heads), semitendinosus, and semimembranosus; biceps femoris short head originates from linea aspera, others from ischial tuberosity; insert on tibial condyles; extend hip and flex knee, opposite actions to quadriceps.
Identification Strategies
- Use patella as a landmark to find rectus femoris and other quadriceps.
- Sartorius is identified by its S-shape across the medial thigh.
- Hamstrings are on the posterior thigh, with medial side containing semimembranosus and semitendinosus.
- Adductors are found on the medial thigh, pulling the limb toward the midline.
Key Terms & Definitions
- Origin — the muscle attachment site on the fixed bone.
- Insertion — the muscle attachment site on the moving bone.
- Action — the movement produced by muscle contraction.
- Abduction — movement away from the midline.
- Adduction — movement towards the midline.
- Flexion — decreasing the angle at a joint.
- Extension — increasing the angle at a joint.
- Iliotibial (IT) Band — a thick band of connective tissue on the lateral thigh.
Action Items / Next Steps
- Practice identifying hip and knee muscles using anatomical diagrams or models.
- Review muscle origins, insertions, and actions for the listed muscles.
- Prepare for upcoming content on lower leg muscles (e.g., gastrocnemius).