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
Sartorius
- 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
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