Muscles and Functions of the Lower Limb

Overview of Muscles and Functions in the Lower Limb

Muscles Producing Flexion at the Knee Joint

• Main Flexors: Three hamstring muscles and two minor flexors, which include:
    - Hamstrings: Semimembranosus, Semitendinosus, Biceps Femoris.
      - Semimembranosus:
        - Arises from the ischial tuberosity.
        - Inserts on the medial side of the knee.
      - Semitendinosus:
        - Arises from the ischial tuberosity.
        - Inserts on the medial side of the knee, close to semimembranosus.
      - Biceps Femoris:
        - Arises from the ischial tuberosity and portion of the femur.
        - Inserts at the head of the fibula.
• Minor Flexors: Sartorius and Gracilis.
    - Sartorius:
      - Arises from the anterior superior iliac spine (ASIS).
      - Inserts close to semitendinosus.
    - Gracilis:
      - Arises from the pubis.
      - Inserts close to semitendinosus.

Functionality of Hamstring Muscles

• Coordinated Actions:
    - Primary actions include extension of the hip and flexion of the knee.
    - The specific function (hip extension or knee flexion) depends on opposing muscle activity:
      - Knee Flexion Resistance: If quadriceps resist knee flexion, the hamstrings extend the hip.
      - Hip Extension Resistance: If hip flexors resist extension, the hamstrings flex the knee.
• Rotational Movements:
    - Hamstring muscles can also produce:
      - Medial rotation at the knee (except biceps femoris)
      - Lateral rotation at the knee (by biceps femoris).

Quadriceps Muscle Group

• Main Extensor of the Knee: Quadriceps is a large muscle group responsible for knee extension. The group includes four heads:
    - Vastus Intermedius:
      - Deepest head, bulges on the front of the femur.
      - Arises from the lateral aspect and anterior surface of the femur.
    - Vastus Medialis:
      - Arises from the medial edge of the linea aspera.
      - Covers vastus intermedius almost completely in the medial aspect.
    - Vastus Lateralis:
      - Arises from the lateral edge of the linea aspera and anterior surface of the greater trochanter.
    - Rectus Femoris:
      - Arises from the ilium just above the hip joint with two parts:
        - Anterior (straight) part from the anterior inferior iliac spine.
        - Posterior (reflected) part from above acetabulum.
• Convergence:
    - All four heads converge on the quadriceps tendon, which inserts on the patella.
• Principal Actions:
    - Extends the knee.
    - Acts as an antigravity muscle in normal movements, important for activities such as walking, climbing, and jumping.

Adductor Canal

• Important structural component located between the vastus medialis and adductor longus:
    - Contains femoral vessels moving from the front of the thigh to the back.
    - Covered by the sartorius muscle.

Summary of Ankle Region Musculature and Movement

• Definitions of Movements:
    - Dorsiflexion: Upward movement of the foot (lifting the front).
    - Plantarflexion: Downward movement (lifting the heel).
    - Eversion: Turning foot outward.
    - Inversion: Turning foot inward.
• Key Muscles:
    - Dorsiflexors:
      - Tibialis Anterior:
        - Arises from lateral surface of upper tibia and interosseous membrane.
        - Inserts on the first cuneiform and base of the first metatarsal.
    - Plantarflexors:
      - Gastrocnemius:
        - Has two heads (medial and lateral) originating from the femur's condyles.
        - Contributes to the formation of the calcaneal (Achilles) tendon.
      - Soleus:
        - Originates from medial edge of the tibia.
      - Plantaris:
        - Assists in plantar flexion but contributes less significantly compared to gastrocnemius and soleus.

Bones of the Leg and their Articulations

• Main Bones:
    - Tibia: Larger of the two leg bones. Articulates with the femur at the knee and the talus at the ankle.
    - Fibula: Smaller bone that stabilizes the ankle joint but does not participate in the knee joint.
• Articulation Points:
    - Talus: Major bone in the ankle joint connecting with both tibia and fibula.
    - Calcaneus: Supports the heel and contributes to various joint movements, including subtalar joint.
• Ligaments:
    - Anterior and posterior tibiofibular ligaments stabilize the fibula and tibia.
    - Deltoid Ligament: Supports the medial side of the ankle, connecting the medial malleolus to talus and has extensive connections to adjacent bones.

Clinical Applications in Physical Therapy

• Importance of understanding lower limb anatomy in rehabilitation settings.
• Implications of joint mobility and muscle strength during rehabilitation.
• Awareness of conditions causing functional limitations and the importance of assessing joint stability in patients with knee or ankle issues.
• Considerations for patient's history during interventions, including any prior surgeries (e.g., knee replacements) and their functional impact on mobility and independence.