anatomy and working of Knee joint. pptx.ppt

knee joint

1. KNEE COMPLEX

2. The Tibiofemoral, or knee, joint is a double
condyloid joint with three degrees of freedom of
angular (rotatory) motion.
Flexion and extension occur in the sagittal plane
around a coronal axis through the epicondyles of
the distal femur,
medial/lateral (internal/external) rotation occur in
the transverse plane about a longitudinal axis
through the lateral side of the medial tibial condyle,
and abduction and adduction can occur in the
frontal plane around an anteroposterior axis.
Medial and lateral compartments of the knee

3. Femur
The proximal articular surface of the knee joint is
composed of the large medial and lateral condyles
of the distal femur.
Because of the obliquity of the shaft of the femur,
the femoral condyles do not lie immediately below
the femoral head but are slightly medial to it.
As a result, the lateral condyle lies more directly in
line with the shaft than does the medial condyle.
The medial condyle therefore must extend further
distally, so that, despite the angulation of the
femur’s shaft, the distal end of the femur remains
essentially horizontal.

5. In the sagittal plane, the condyles have a convex
shape, with a smaller radius of curvature
posteriorly
Although the distal femur as a whole has very little
curvature in the frontal plane, both the medial
and lateral condyles individually exhibit a slight
convexity in the frontal plane.

6. The lateral femoral condyle is shifted anteriorly in
relation to the medial femoral condyle. In addition,
the articular surface of the lateral condyle is shorter
than the articular surface of the medial condyle.
When the femur is examined through an inferior
view, the lateral condyle appears at first glance to
be longer.
 However, when the patellofemoral surface is
excluded, it can be seen that the lateral tibial
surface ends before the medial condyle

8. Tibia
The asymmetrical medial and lateral tibial condyles
or plateaus constitute the distal articular surface of
the knee joint.
The medial tibial plateau is longer in the
anteroposterior direction than is the lateral plateau;
however, the lateral tibial articular cartilage is
thicker than the articular cartilage on the medial
side.
The proximal tibia is larger than the shaft and,
consequently, overhangs the shaft posteriorly .
Accompanying this posterior overhang, the tibial
plateau slopes posteriorly approximately,

9. The medial and lateral tibial condyles are
separated by a roughened area and two bony
spines called the intercondylar tubercles. These
tubercles become lodged in the intercondylar
notch of the femur during knee extension.
The tibial plateaus are predominantly flat, with a
slight convexity at the anterior and posterior
margins, which suggests that the bony architecture
of the tibial plateaus does not match up well with
the convexity of the femoral condyle. Because of
this lack of bony stability, accessory joint structures
(menisci) are necessary to improve joint
congruency

10. Tibiofemoral Alignment
and Weight-Bearing Forces
The anatomic (longitudinal) axis of the femur,
as already noted, is oblique, directed inferiorly
and medially from its proximal to distal end. The
anatomic axis of the tibia is directed almost
vertically.
Consequently, the femoral and tibial longitudinal
axes normally form an angle medially at the
knee joint of 180 to 185

11. That is, the femur is angled up to 5 off vertical,
creating a slight physiologic (normal) valgus
angle at the knee.
If the medial tibiofemoral angle is greater than
185, an abnormal condition called genu
valgum (“knock knees”) exists.
If the medial tibiofemoral angle is 175 or less,
the resulting abnormality is called genu varum
(“bow legs”).

12. Each condition alters the compressive and
tensile stresses on the medial and lateral
compartments of the knee joint.
Mechanical axis, or weight-bearing line

13. Menisci
Tibiofemoral congruence is improved by the
medial and lateral menisci, forming concavities
into which the femoral condyles sit
In addition to enhancing joint congruence,
these accessory joint structures play an
important role in distributing weight-bearing
forces, in reducing friction between the tibia
and the femur, and in serving as shock
absorbers.

14. The medial meniscus is C-shaped, whereas the
lateral meniscus forms four fifths of a
circle.Lying within the tibiofemoral joint, the
menisci are located on top of the tibial condyles,
covering one half to two thirds of the articular
surface of the tibial plateau.

15. Meniscal Attachments
The open anterior and posterior ends of the
menisci are called the anterior and posterior
horns.
Anteriorly, the menisci are connected to each
other by the transverse ligament.
Both menisci are also attached directly or
indirectly to the patella via the patellomeniscal
ligaments, which are anterior capsular
thickenings.

16. At the periphery, the menisci are connected to the
tibial condyle by the coronary ligaments, which
are composed of fibers from the knee joint capsule.
The medial meniscus has less relative motion than
does the lateral meniscus, and it is more firmly
attached to the joint capsule through medial
thickening of the joint capsule that extends distally
from the femur to the tibia.
This capsular thickening, referred to as the deep
portion of the medial collateral ligament (MCL),
further restricts the motion of the medial meniscus

17. The anterior and posterior horns of the medial
meniscus are attached to the anterior cruciate
ligament (ACL) and posterior cruciate
ligament (PCL).
Meniscal Nutrition and Innervation

18. Joint Capsule
Given the incongruence of the knee joint, even
with the improvements provided by the menisci,
joint stability is heavily dependent on the
surrounding joint structures.
The joint capsule that encloses the tibiofemoral
and patellofemoral joints is large and lax. It is
grossly composed of an exterior or superficial
fibrous layer and a thinner internal synovial
membrane that is even more complex than the
already complex fibrous portion.

19. In general, the outer or fibrous portion of the
capsule is firmly attached to the inferior aspect
of the femur and the superior portion of the tibia.
Posteriorly, the capsule is attached proximally to
the posterior margins of the femoral condyles
and intercondylar notch and distally to the
posterior tibial condyle.

20. Synovial Layer of the Joint Capsule
Fibrous Layer of the Joint Capsule

21. Ligaments
The roles of the various ligaments of the knee
have received extensive attention, which
reflects their importance for knee joint stability
and the frequency with which function is
disrupted through injury

22. 1. excessive knee extension
2. varus and valgus stresses at the knee (attempted
adduction or abduction of the tibia, respectively)
3. anterior or posterior displacement of the tibia
beneath the femur
4. medial or lateral rotation of the tibia beneath
theFemur
5. combinations of anteroposterior displacements and
rotations of the tibia, together known as rotatory
stabilization of the tibia

23. Medial Collateral Ligament
The MCL can be divided into a superficial portion
and a deep portion that are separated by a bursa.
The superficial portion of the MCL arises proximally
from the medial femoral epicondyle and travels
distally to insert into the medial aspect of the
proximal tibia distal to the pes anserinus.
The deep portion of the MCL is continuous with the
joint capsule, originates from the inferior aspect of
the medial femoral condyle, and inserts on the
proximal aspect of the medial tibial plateau.
Throughout its course of travel, the deep portion of
the MCL is rigidly affixed to the medial border of
the medial meniscus

24. Lateral Collateral Ligament
The lateral collateral ligament (LCL) is located
on the lateral side of the tibiofemoral joint,
beginning proximally from the lateral femoral
condyle. The LCL then travels distally to the
fibular head, where it joins with the tendon of
the biceps femoris muscle to form the
conjoined tendon.

25. Anterior Cruciate Ligament
The ACL is attached to the anterior tibial spine,
where it extends superiorly and posteriorly to
attach to the posteromedial aspect of the lateral
femoral condyle.
 The ACL courses posteriorly, laterally, and
superiorly from tibia to femur. In addition, the
ACL twists inwardly (medially) as it travels
proximally.
 The major blood supply to the ACL arises
primarily from the middle genicular artery

26. The ACL may also be considered to consist of two
separate bands that wrap around each other.
Each of these bands is thought to have a
different role in controlling tibiofemoral motion.
The anteromedial band (AMB) and the
posterolateral band (PLB) are each named
for their origins on the tibia.

27. Posterior Cruciate Ligament
The PCL attaches distally to the posterior tibial
spine and travels superiorly and somewhat
anteriorly to attach to the lateral aspect of the
medial femoral condyle.

28. KINEMATICS OF KNEE JOINT
Kinematics defines the range of motion and
describes the surfaces motion of a joint in three
planes :
frontal (coronal or longitudnal)
sagittal
Transverse

29. The primary angular (or rotatory) motion of the
tibiofemoral joint is flexion/extension, although
both medial/lateral (internal/external) rotation
and varus/ valgus (adduction/adduction)
motions can also occur to a lesser extent.
the angular motions, translation in an
anteroposterior direction is common on both
the medial and lateral tibial plateaus; to a lesser
extent, medial and lateral translations can
occur in response to varus and valgus forces.

30. Flexion/Extension
The axis for tibiofemoral flexion and extension
can be simplified as a horizontal line passing
through the femoral epicondyles
Transepicondylar axis represents an accurate
estimate of the axis for flexion and extension.
Much of the shift in the axis can be attributed to
the incongruence of the joint surfaces.

31. If the femoral condyles were permitted to roll
posteriorly on the tibial plateau, the femur would
run out of tibia and limit the flexion excursion
For the femoral condyles to continue to roll as
flexion increases without leaving the tibial
plateau, the femoral condyles must
simultaneously glide anteriorly

32. The initiation of knee flexion (0 to 25) as the flexion
continues, the rolling of the femoral condyles is
accompanied by a simultaneous anterior glide.
Extension of the knee from flexion is essentially a
reversal of this motion.
the initial forward rolling, the femoral condyles
glide posteriorly just enough to continue extension
of the femur as an almost pure spin of the femoral
condyles on the tibial plateau

33. When the tibia is flexing on a fixed femur, the tibia
both rolls and glides posteriorly on the relatively
fixed femoral condyles.
Extension of the tibia on a fixed femur
incorporates an anterior roll and glide of the
tibial plateau on the fixed femur

34. Role of the Cruciate Ligaments and
Menisci
in Flexion/Extension
The arthrokinematics associated with tibiofemoral
flexion and extension are somewhat dictated by
the presence of the cruciate ligaments.
the cruciate ligaments are assumed to be rigid
segments with a constant length, posterior
rolling of the femur during knee flexion would
cause the “rigid” ACL to tighten

35. Continued rolling of the femur would result in
the taut ACL’s simultaneously creating an
anterior translational force on the femoral
condyles
The anterior glide of the femur during flexion
may be further facilitated by the shape of the
menisci.
The wedge shape of the menisci posteriorly
forces the femoral condyle to roll “uphill” as the
knee flexes.

36. The oblique contact force of the menisci on the
femur helps guide the femur anteriorly during
flexion while the reaction force of the femur on
the menisci deforms the menisci posteriorly on
the tibial plateau.
The motion (or distortion) of the menisci is an
important component of tibiofemoral flexion and
extension

37. During knee flexion, for example, the
semimembranosus exerts a posterior pull on the
medial meniscus whereas the popliteus assists
with deformation of the lateral meniscus.

38. Flexion/Extension Range of Motion
Passive range of knee flexion is generally
considered to be 130° to 140°.
During an activity such as squatting, knee flexion
may reach as much as 160° as the hip and knee
are both flexed and the body weight is super-
imposed on the joint.

39. Knee joint extension (or hyperextension) up to 5°
is considered within normal limits.
Excessive knee hyperextension (i.e., beyond 5° of
hyperextension) is termed genu recurvatum.

40. Medial/Lateral Rotation
Medial and lateral rotation of the knee joint are
angular motions that are named for the motion
(or relative motion) of the tibia on the femur
Consequently, the medial condyle acts as the
pivot point while the lateral condyles move
through a greater arc of motion, regardless of
the direction of rotation .

41. the tibia laterally rotates on the femur, the medial
tibial condyle moves only slightly anteriorly on
the relatively fixed medial femoral condyle
During tibial medial rotation, the medial tibial
condyle moves only slightly posteriorly, whereas
the lateral condyle moves anteriorly through a
larger arc of motion.

42. Axial rotation is permitted by articular
incongruence and ligamentous laxity.
Therefore, the range of knee joint rotation
depends on the flexion/extension position of the
knee.
As the knee flexes toward 90, capsular and
ligamentous laxity increase, the tibial tubercles
are no longer in the intercondylar notch, and
the condyles of the tibia and femur are free to
move on each other.

43. At 90°, the total medial/lateral rotation available is
approximately 35°, with the range for lateral
rotation being slightly greater (0° to 20°) than
the range for medial rotation (0° to 15°).

44. Valgus (Abduction)/Varus
(Adduction)
Frontal plane ROM is typically only 8° at full
extension, and 13° with 20° of knee flexion.
Excessive frontal plane motion could indicate
ligamentous insufficiency.
When there is ligamentous laxity, the excessive
varus/valgus motion or increased dynamic
activity of muscles attempting to control this
excessive motion

45. Coupled Motions
The true flexion/extension axis is not
perpendicular to the shafts of the femur and tibia.
flexion and extension do not occur as pure
sagittal plane motions but include frontal plane
components termed “coupled motions”
, the medial femoral condyle lies slightly distal to
the lateral femoral condyle, which results in a
physiologic valgus angle in the extended knee
that is similar to the physiologic valgus angle that
exists at the elbow.

46. Automatic or Locking Mechanism of
the Knee
There is an obligatory lateral rotation of the tibia
that accompanies the final stages of knee
extension that is not voluntary or produced by
muscular forces. This coupled motion (lateral
rotation with extension) is referred to as
automatic or terminal rotation.
Consequently, during the last 30° of knee
extension (30° to 0°), the shorter lateral tibial
plateau/femoral condyle pair completes its
rolling-gliding motion

47. Increasing tension in the knee joint ligaments as
the knee approaches full extension may also
contribute to the obligatory rotational motion,
bringing the knee joint into its close-packed or
locked position.
The tibial tubercles become lodged in the
intercondylar notch, the menisci are tightly
interposed between the tibial and femoral
condyles, and the ligaments are taut.
Consequently, automatic rotation is also known as
the locking or screw home mechanism of the knee.

48. A flexion force will automatically result in medial
rotation of the tibia because the longer medial
side will move before the shorter lateral
compartment.

49. This automatic rotation or locking of the knee
occurs in both weight-bearing and non–weight-
bearing knee joint function.
In weight-bearing, the freely moving femur
medially rotates on the relatively fixed tibia
during the last 30 of extension.
Unlocking, consequently, is brought about by
lateral rotation of the femur on the tibia before
flexion can proceed.

50. The motions of the knee joint, exclusive of
automatic rotation, are produced to a great
extent by the muscles that cross the joint.

51. Kinetics
 The muscles that cross the knee are typically
thought of as either flexors or extensors,
because flexion and extension are the primary
motions occurring at the tibiofemoral joint.
 Each of the muscles that flex and extend the
knee has a moment arm (MA) that is capable of
generating both frontal and transverse plane
motions, although the MAs for these latter
motions are generally small.

52. Knee Flexor Group :-
 There are seven muscles that flex the knee.
These are
the semimembranosus, semitendinosus, biceps
femoris (long and short heads), sartorius,
gracilis, popliteus, and gastrocnemius muscles
As two-joint muscles, the ability to produce
effective force at the knee is influenced by the
relative position of the other joint over which that
muscle crosses.

53. Five of the flexors (the popliteus, gracilis, sartorius,
semimembranosus, and semitendinosus muscles)
have the potential to medially rotate the tibia on a
fixed femur, whereas the biceps femoris has a MA
capable of laterally rotating the tibia
The lateral muscles (biceps femoris, lateral head of
the gastrocnemius, and the popliteus) are capable
of producing valgus moments at the knee, whereas
those on the medial side of the joint
(semimembranosus, semitendinosus, medial head
of the gastrocnemius, sartorius, and gracilis) can
generate varus moments

54. The rest of the hamstring muscles cross both the
hip (as extensors) and the knee (as flexors);
therefore, their efficacy in producing force at the
knee is dictated by the angle of the hip joint.
Greater hamstring force is produced with the hip
in flexion when the hamstrings are lengthened
over that joint, regardless of knee position.

55. When the two-joint hamstrings are required to
contract with the hip extended and the knee
flexed to 90 or more, the hamstrings must
shorten over both the hip and over the knee.
The hamstrings will weaken as knee flexion
proceeds because not only are they
approaching maximal shortening capability, but
also the muscle group must overcome the
increasing tension in the rectus femoris muscle
that is approaching passive insufficiency.

56. In non–weight-bearing activities,
the hamstrings generate a posterior shearing
force of the tibia on the femur that increases as
knee flexion increases, peaking between 75 and
90 of knee flexion. This posterior shear or
posterior translational force can reduce strain on
the ACL

57. Knee Extensor Group:-
The four extensors of the knee are known collectively as the
quadriceps femoris muscle.
 rectus femoris muscle, which crosses the hip and knee The
vastus
intermedius, vastus lateralis, and vastus medialis muscles
originate on the femur and merge with the rectus femoris
muscle into a common tendon, called the quadriceps tendon.
The quadriceps tendon inserts into the proximal aspect of the
patella and then continues distally past the patella, where it is
known as the patellar tendon (or patellar ligament). The
patellar tendon runs from the apex of the patella into the
proximal portion of the tibial tuberosity. The vastus medialis
and vastus lateralis also insert directly into the medial and
lateral aspects of the patella by way of the retinacular fibers of
the joint capsule

58. The pull of the vastus lateralis muscle alone was
found to be 12 to 15 lateral to the long axis of
the femur
The upper fibers were angled 15 to 18 medially to
the femoral shaft, whereas the distal fibers were
angled as much as 50 to 55 medially.

59. Because of the drastically different orientation of
the upper and lower fibers of the vastus
medialis muscle, the upper fibers are commonly
referred to as the vastus medialis longus (VML),
and the lower fibers are referred to as the
vastus medialis oblique (VMO).

60.  Patellar Influence on Quadriceps Muscle
Function :-
 the patella lengthens the MA of the quadriceps
by increasing the distance of the quadriceps
tendon and patellar tendon from the axis of the
knee joint. The patella, as an anatomic pulley,
deflects the action line of the quadriceps
femoris muscle away from the joint center,
increasing the angle of pull and the ability of the
muscle to generate an extension torque.

61. The patella’s role in increasing the angle of pull of
the quadriceps enhances the quadriceps’ torque
production but at a cost.

62. Knee Stabilizer
 A-P/hyperextension
Anterior cruciate ligament
Iliotibial band
Hamstring muscles
Soleus muscle (in weight-bearing)
Gluteus maximus muscle (in weight-bearing)
Posterior cruciate ligament
Meniscofemoral ligaments
Quadriceps muscle
Popliteus muscle
Medial and lateral heads of gastrocnemius

63.  Varus/valgus stabilizers :-
 Medial collateral ligament
 Anterior cruciate ligament
 Posterior cruciate ligament
 Arcuate ligament
 Posterior oblique ligament
 Sartorius muscle
 Gracilis muscle Pes anserinus
 Semitendinosus muscle
 Semimembranosus muscle
 Medial head of gastrocnemius muscle
 Lateral collateral ligament
 Iliotibial band
 Anterior cruciate ligament
 Posterior cruciate ligament
 Arcuate ligament
 Posterior oblique ligament
 Biceps femoris muscle
 Lateral head of gastrocnemius muscle

64. Internal/external rotational stabilizers
Anterior cruciate ligament
Posterior cruciate ligament
Posteromedial capsule [80]
Meniscofemoral ligament
Biceps femoris
Posterolateral capsule [80]
Medial collateral ligament
Lateral collateral ligament
Popliteus muscle
Sartorius muscle
Gracilis muscle
Semitendinosus muscle
Semimembranosus muscle