Muscle of the Thigh Region

acl adductor adductor brevis adductor longus adductor magnus adductors anterior cruciate ligament articularis genu biceps femoris gastrocnemius gracilis hamstrings knee flexor muscles knee ligaments locking mechanism of knee locking mechanism of the knee locking of the knee movement of the patella muscles of the thigh muscles of the upper leg patella patella stability pcl pectineus popliteus posterior cruciate ligament quad muscles quadriceps tendon quads rectus femoris sartorius semimembranosus semitendinosus unlocking of the knee vastus intermedius vastus lateralis vastus medialis

Muscles of the Thigh Region Physiotherapy Solihull Simon Evans

The Compartments

As with any other body segment the thigh region is divided into compartments containing functional groups

Divisions are made by the intermuscular septa

3 compartments to consider:

  • Anterior
  • Posterior 
  • Medial

Anterior Compartment

  • Formed by the quadriceps femoris group and sartorius
  • The Quadriceps Femoris group is made up of 4 muscles-
    • Rectus femoris (crosses hip and knee)
    • Vastus Medialis,
    • Intermedius (single joint muscle)
    • Lateralis (single joint muscle)
  • All converge to form the quadriceps tendon inserting into the tibial tuberosity (note presence of patella)

      Rectus Femoris

      • Only portion of quadriceps to cross hip and knee – implication for function
      • Bipennate muscle
      • O: From 2 Heads:
        • Straight head – from AIIS
        • Reflected head – from grove above acetabulum and anterior hip joint capsule
      • I: Forms superficial part of patella tendon

      Vastus Lateralis

      • O: Via aponeurosis
        • Upper ½ of intertrochanteric line
        • Anterior and lower border of greater trochanter
        • Lateral lip of gluteal tuberosity
        • Upper ½ of lateral lip of linea aspera
        • Anterior surface of lateral intermuscular septum
      • I: Forms lateral part of patella tendon (into base and lateral border of patella) 

      Vastus Medialis

      • Upper 2/3 of medial supracondylar ridge
      • Medial lip of linea aspera
      • Spiral line
      • Lower ½ of intertrochanteric line
      • Anterior surface of medial intermuscular septum 

      Vastus Intermedius / Articularis Genu

      • Deepest of 4 quadriceps (under rectus femoris)
      • From upper 2/3s of anterior and lateral surface of shaft of femur
      • Articularis genu – few fibres from V. intermedius attach to suprapatellar pouch – contracts with quads to prevent impingement of synovial membrane

      Collective action of Quads

      • Collective action of the Quads:-
        • On contraction quads produce extension of the knee
        • Rectus femoris is also a hip flexor
      • Functions
        • Sit to stand/stand to sit
        • Stairs
        • Gait/running
        • Kicking
        • V. med also prevents lateral excursion of patella
      • All 4 quads are supplied via the femoral nerve L2, 3 and 4 

      The Quadriceps Tendon

      • All quads contribute to the formation of the quadriceps tendon which inserts onto the upper part of the tibial tuberosity
      • Patella – sesamoid bone – increases the lever arm of quads
      • Medial and lateral retinacula further stabilise patella
      • Movement of patella greatly influenced by balanced pull of quads and tension in inert structures

      Patella Stability

      • Dependent on the degree of flexion at the knee
      • In extension controlled by balance of forces from quads, patella tendon, patella retinacula and inert structures attaching to patella

      Movement of the Patella

      • During flexion and extension of the knee the patella moves in/out of the intercondylar area of the femur
      • This has the effect of stabilising the patella with the knee in flexion

      Medial Compartment

      • Contains the adductor group
        • Gracilis
        • Pectineus
        • Adductor Longus, brevis and magnus
      • All arise from ischial tuberosity & ramus and pubis and rami

      Muscles acting at the knee joint

      • Flexors of the knee joint:
        • Biceps femoris
        • Semitendinosus
        • Semimembranosus
        • Sartorius
        • Gracilis
        • (Popliteus)
        • Gastrocnemius (to be discussed in detail as a plantarflexor of the ankle joint)
      • All discussed in the muscles acting over the hip joint


        • Strap like muscle from ASIS to pes anserine insertion (on the medial side of the upper shaft of tibia)
        • Action – crossing legs into ‘Tailor’s’ position
        • Forms boundary of femoral triangle
        • NS: Femoral nerve L2,3 & 4

        Posterior Compartment

        • Contains the 3 hamstring muscles 
        • Hamstrings are made up of biceps femoris, semimembranosus & semitendinosus

        Actions of the Hamstrings

        • All extend the hip and flex the knee
        • Biceps femoris is a lateral rotator of the flexed knee
        • Semitendinosus and semimembranosus are medial rotators of the flexed knee
        • Functionally important in controlling knee extension during gait and running

        Muscles acting over the Knee Joint

        • Muscles producing medial rotation at the knee
          • Semitendinosus
          • Semimembranosus
          • Sartorius
          • Gracilis
          • Popliteus
          • Muscles producing lateral rotation at the knee
            • Biceps femoris

            Anterior and Posterior Stability

            • The knee joint is inherently unstable relying on ligamentous structures for stability
            • Secondary support is offered by the tendons crossing the knee joint anteriorly and posteriorly 
            • Work with ACL and PCL to prevent excessive forward and backward movement of the tibia

            Mediolateral and Rotational Stability

            • Abduction and adduction is limited mainly by the collateral ligaments – varus and valgus - Work with ACL and PCL
            • Lateral rotation is limited mainly by the MCL and medial hamstrings
            • Medial rotation is limited mainly by the cruciates, biceps femoris and ITB

            Physiological vs Accessory Movements

            • Physiological movements are movements that can occur actively at a joint
            • Accessory movements are movements that cannot be produced in isolation by primary muscle action (e.g. anterior glide, abduction at the knee etc)
            • Accessory movements often (but not always) form an integral part of a physiological movement (see spin, roll and slide handout)

            Muscles acting at the knee joint

            • Medial and lateral rotation can occur physiologically when the knee is flexed
            • It also occurs as an accessory movement during the terminal phase of extension in order to lock the knee

            Locking Mechanism of Knee

            • In final 20 degrees of extension increased tension in the cruciate ligaments and their oblique orientation, causes lateral rotation of the tibia
            • Shape and orientation of the articular surfaces permits this motion – longer medial femoral condyle

            Conjunct vs Adjunct Rotation

            • When rotation occurs by primary muscle action (i.e. physiologically) it is termed
              • Adjunct rotation
            • When rotation occurs as a result of tension in the passive structures of the knee (i.e. accessory motion) it is termed
              • Conjunct rotation

            Locking Mechanism of the Knee

            • Extension of knee increases tension in cruciates
            • Obliquity of cruciates pull tibia into lateral rotation (aided by shape of femoral condyles)
            • Rotation causes increases tension in collateral ligaments
            • Leads to compression of articular surfaces and deformation of menisci

            Unlocking of the Knee

            • To unlock the knee medial rotation of the tibiofemoral is needed
            • Partly brought about by recoil of ligamentous structures
            • Partly brought about by contraction of popliteus


            • Orientated obliquely across the posterior aspect of the knee
            • O: Lateral surface of lateral condyle of femur – intracapsular tendon
            • R: Obliquely downward and medially
            • I: Posterior aspect of medial condyle of tibia above soleal line

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