HA Mod 3 Lecture Keys (2nd Half)

Gluteus Maximus in Gait: Initial Contact

Works Isometrically

Gluteus Maximus in Gait: Loading Response

Works Concentrically (to extend hip)

Gluteus Medius in Gait: Single Leg Stance

Prevents pelvic drop on the opposite (swing) side

Gluteus Medius in Gait: Midstance

Stabilizes the pelvis in the coronal plane

Gluteus Medius during single leg stance

Acts as the primary stabilizer of the pelvis; creates abduction force to prevent pelvic drop on swing side (Trendelenburg sign)

Gluteus Maximus architecture

Large cross-sectional area for power; oblique fibers capture IT band for knee stability

Hamstrings vs. Glutes architecture

Hamstrings are 2-joint muscles (active insufficiency risk); Glutes are 1-joint (power generator)

Rectus Femoris (Two-Joint): Joints

Crosses the Hip (Anterior) and Knee (Anterior)

Rectus Femoris (Two-Joint): Action

Flexes the Hip and Extends the Knee

Sartorius (Two-Joint): Joints

Crosses the Hip (Anterior) and Knee (Medial)

Sartorius (Two-Joint): Action

Flexes

Hamstrings (Two-Joint): Muscles Includes

Semimembranosus

Hamstrings (Two-Joint): Joints

Crosses the Hip (Posterior) and Knee (Posterior)

Hamstrings (Two-Joint): Action

Extends the Hip and Flexes the Knee

Biceps Femoris Short Head

Single-Joint muscle (only crosses the knee)

Gracilis (Two-Joint): Joints

Crosses the Hip (Medial) and Knee (Medial)

Gracilis (Two-Joint): Action

Adducts Hip + Flexes Knee

Tensor Fasciae Latae (Two-Joint): Joints

Crosses the Hip; transmits force via the IT Band across the Knee

Tensor Fasciae Latae (Two-Joint): Action

Hip Flexion/Abduction + Stabilizes the Knee (via ITB)

Gastrocnemius (Two-Joint): Joints

Crosses Knee (Posterior) and Ankle

Gastrocnemius (Two-Joint): Action

Knee Flexion + Ankle Plantarflexion

Single-Joint Examples

Iliacus (Hip Flexion); Gluteus Maximus (Hip Extension); Gluteus Medius/Minimus (Abduction); Vastus Group (Knee Extension)

Active Insufficiency Definition

Muscle fails to contract effectively when shortened over both joints simultaneously (myosin can't find new actin sites)

Rectus Femoris Active Insufficiency

Occurs during Hip Flexion + Knee Extension (e.g.

Hamstrings Active Insufficiency

Occurs during Hip Extension + Knee Flexion; muscle is "cramped" and weak

Passive Insufficiency Definition

Muscle is overstretched

Rectus Femoris Passive Insufficiency

Occurs during Hip Extension + Knee Flexion (e.g.

Hamstrings Passive Insufficiency

Occurs during Hip Flexion + Knee Extension (e.g.

Gastrocnemius Passive Insufficiency

Occurs during Knee Extension + Ankle Dorsiflexion; limits dorsiflexion with straight leg

Strap / Parallel Muscles Function

Designed for Excursion (Speed and ROM) rather than raw force; e.g.

Pennate Muscles Function

Designed for Force production; fibers run obliquely to tendon; e.g.

Fan-Shaped Muscles Function

Versatility; different fibers have different actions; e.g. o   Anterior fibers: Medial Rotation.

o   Posterior fibers: Lateral Rotation.

o   All fibers: Abduction.

Adductor Inversion of Action

In Hip Extension

Piriformis Inversion of Action

In Extension: Lateral Rotation; In Flexion (>60°): Abduction and Medial Rotation

Gluteus Medius Leverage in Stance

Must generate force ~2x body weight to counter gravity's torque and prevent pelvic drop (Trendelenburg)

Iliotibial Band (ITB)

Fascial thickening acting as a tendon for TFL and Gluteus Maximus; stabilizes the lateral knee

Palpation: Gluteus Medius

Palpate superior to greater trochanter; vital for checking stability in single-leg stance

Palpation: Adductors

Adductor Longus tendon is prominent in the groin; Gracilis is on medial thigh

Gluteus Maximus Creates (Concentric)

Hip Extension and Lateral Rotation

Gluteus Maximus Controls (Eccentric)

Hip Flexion (e.g.

Gluteus Maximus Constrains (Isometric)

Hip Flexion (prevents unwanted forward motion of the pelvis)

Gluteus Medius Creates (Concentric)

Hip Abduction

Gluteus Medius Controls (Eccentric)

Hip Adduction (controls pelvic drop on opposite side during stance)

Gluteus Medius Constrains (Isometric)

Hip Adduction (prevents pelvic drop

Hamstrings Create (Concentric)

Knee Flexion and Hip Extension

Hamstrings Control (Eccentric)

Knee Extension (swing phase) and Hip Flexion

Hamstrings Constrain (Isometric)

Hip Flexion (limits forward pelvic tilt

Iliopsoas Creates (Concentric)

Hip Flexion

Iliopsoas Controls (Eccentric)

Hip Extension (e.g.

Iliopsoas Constrains (Isometric)

Hip Extension (limits backward movement of the pelvis on femur)

Adductors Create (Concentric)

Hip Adduction

Adductors Control (Eccentric)

Hip Abduction (e.g.

Adductors Constrain (Isometric)

Hip Abduction (prevents leg from moving away from midline)

Anterior Hip Muscles

Iliopsoas

Medial Hip Muscles

Pectineus

Posterior Hip Muscles

Gluteus Maximus

Lateral Hip Muscles

Gluteus Medius

Hip Flexion Prime Movers

Iliopsoas

Hip Extension Prime Movers

Gluteus Maximus

Hip Adduction Prime Movers

Adductor Magnus

Hip Abduction Prime Movers

Gluteus Medius

Hip Lateral Rotation Prime Movers

Gluteus Maximus

Hip Medial Rotation Prime Movers

Gluteus Minimus

Intrinsic Hip Muscle Feature

Originates on Ilium

Extrinsic Hip Muscle Feature

Originates on Lumbar Spine or Thoracic Cage; Inserts on Femur or Tibia; Primary Action: Move Hip AND Lumbar Spine

Intrinsic Hip Muscle Examples

Gluteals

Extrinsic Hip Muscle Examples

Psoas Major (Lumbar to Femur)