The knee joint is a modified hinge joint that allows flexion and extension. It is supported by ligaments including the ACL, PCL, MCL and LCL. The joint is lined by a synovial membrane and contains two menisci that absorb shock and deepen the tibial surfaces. Flexion is powered by the hamstrings while extension is powered by the quadriceps femoris muscle. The knee provides stability during weight bearing and locomotion.

1. KNEE JOINT

2. Osteology
• Distal Femur with Proximal Tibia
• Largest Joint Cavity in the Body
• A modified hinge joint with significant passive
rotation
• Technically, one degree of freedom
(Flexion/Extension) but passive rotary
component is essential
• Unites the two longest levers in the body

3. Support
• Knee supports the weight of the body and
transmits forces from the ground
• Functional stability of the joint is derived from
the passive restraint of the ligaments, the
active support of muscles, the joint geometry,
and the compressive forces pushing the bones
together

4. Joint Capsule
• Largest in body
• Surrounds entire joint, except anteriorly
• Originally (in utero) is three capsule that merge into
one
• MCL – flat band, attached above medial condyle of the
femur and below to the medial surface of the shaft of
the tibia – resists lateral displacement
• LCL – cordlike, attached above the lateral condyle of
femur and below the head of the fibula – resists medial
displacement

5. Capsule
• Oblique Popliteal – derived from
semimembranosus on posterior aspect of the
capsule, runs from that tendon to medial
aspect of the lateral femoral condyle
(posteriorly)
• Arcuate popliteal from head of fibula, runs
over the popliteus muscle to attach into
posterior joint capsule

6. CAPSULE
• It is absent Anteriorly.
• It is
• Replaced by :
• Quadriceps femoris
tendon.
• Patella.
• Ligamentum patellae.

7. CAPSULE
• Posteriorly :
• (a) Superior :
• Attached proximal to the
articular margins of the
femoral condyles and to
the intercondylar fossa
• It is deficient above the
lateral condyle for the
passage of tendon of
popliteus

8. Posterior Capsule

9. CAPSULE
• (b) Inferior :
• Attached to the tibia
EXCEPT when the
tendon of Popliteus
crosses the bone.

10. EXTRACAPSULAR LIGAMENTS
• 1. Ligamentum Patellae
• It is the inter mediate part
of the tendon of quadriceps
femoris .It is supported by
the patellar retinaculi
(expansions from the vasti)
• They strengthen the
capsule on each side.

11. 2. TIBIAL (MEDIAL) COLLATERAL
• A flat band.
• Attachment:
• Above to the medial
condyle of the femur.
• Below to the medial
surface of the shaft of the
tibia.
• Firmly attached to the
medial meniscus.

12. Collaterals

13. 3. LATERAL (FIBULAR) COLLATERAL
• Cord like.
• Attachment :
• Above : lateral condyle of
the femur.
• Below : head of the
fibula.
• Separated from the
lateral meniscus by the
tendon of popliteus.

14. Collaterals

15. 4. OBLIQUE POPLITEAL LIG.
• An expansion of the
Semimembranosus.
• It strengthens the
capsule posteriorly.

16. CRUCIATE LIGAMENTS
• They are the main
bond between the
femur and tibia
throughout the joint’s
movements.
• They Cross each other
within the joint cavity.
• They are named
Anterior and Posterior
according to their
tibial attachments.

17. ANTERIOR CRUCIATE
• Tibial attachment :
• Anterior intercondylar
area.
• Course :
• Upward, backward and
laterally.
• Femoral attachment:
• Posterior part of medial
surface of the lateral
condyle.

18. ANTERIOR CRUCIATE
• FUNCTION
• Prevent posterior
displacement of the
femur on the tibia
and the tibia from
being pulled
anteriorly when the
knee joint is flexed.
• It is taught in hyper
extension.

19. POSTERIOR CRUCIATE
• Tibial attachment :
• posterior inter condylar
area.
• Direction:
• upward, forward and
medially.
• Femoral attachment:
• Anterior part of the lateral
surface of the medial
condyle.

20. POSTERIOR CRUCIATE
• Function:
• prevents anterior
displacement of
the femur on the
tibia and the tibia
from being pulled
posteriorly when
the knee joint is
flexed.
• It is taught in hyper
flexion.

22. Menisci
• The surface of the tibia is covered by fibrocartilaginous
menisci - They:
– Enhance the joint stability by deepening the contact
surface
– They help with shock absorption by transmitting ½ of
weight bearing load in full extension and some in
flexion as well
– They protect the articular cartilage
– They transmit the load across the surface of the joint,
thus reducing the load per unit area on the tibio-
femoral contact sites. The contact area in the joint is
reduced 50% when the menisci are absent

23. Menisci

24. Menisci
• In hi load situations, 70% of the load is absorbed
by the menisci, especially the lateral meniscus
• The menisci assist in lubrication of the joint by
acting as a space filling mechanism, more fluid is
dispersed to the surface of tibia and femur
• 20% increase in friction following meniscal
removal
• Medial Meniscus – larger, reflects the shape of
medial tibial condyle A + P horns – attached to
medial collateral ligament and basically immobile
• Lateral Meniscus – smaller, tighter, almost a
complete circle A+ P horns – NOT attached to
lateral collateral ligament

25. MENISCI
• C shaped sheets of fibro
cartilage.
• The peripheral border is
thick and attached to the
capsule.
• The inner border is thin
and concave and forms a
free edge.

26. MENISC
• The upper concave
surfaces are in contact
with the femoral
condyles.
• The lower flat surfaces
are in contact with the
tibial condyles.

27. MENISCI
• Functions :
• 1. Deepen the
tibial articular
surfaces.
• 2. Act as cushions
between the two
bones.

28. MEDIAL MENISCUS
• Crescentic in shape.
• More liable to injury
due to its
attachment to the
medial collateral
ligament and to the
capsule.
• It is relatively
immobile.

29. Menisci

30. LATERAL MENISCUS
• More rounded in shape.
• Its anterior and posterior
ends lie within the ends of
the medial meniscus.
• Posteriorly it is separated
from the fibular collateral
ligament by the tendon of
popliteus.
• Less liable to injury.

31. Menisci - Attachments
• Transverse ligament anteriorly
• Meniscopatellar fibers or ligaments: Fibrous bands
connecting the anterior horns of both menisci to the
medial and lateral retinaculum
• The medial collateral ligament attaches to the medial
meniscus
• The tendon of semimenbranosis sends fibers to the
posterior edge of medial meniscus
• The popliteus muscle sends fibers to the lateral meniscus
• The meniscofemoral ligament extends from the lateral
meniscus (post) to the inside of the medial condyle near
the PCL
• The coronary liagaments – meniscotibial

32. Menisci

33. Meniscal Attachments

34. INJURY OF THE MENISCI
• The menisci are frequently
injured especially in
footballers and cricketers.
• The medial is torn three
times more often than the
lateral.
• The injury is produced by the
rotation of the femur on the
tibia or the reverse with the
knee joint partially flexed and
carries the weight of the
body.

35. INJURY OF THE MENISCI
• The torn part of the
meniscus is wedged
between the tibial and
femoral condyles.
• No further movement
is allowed and the
joint is kept locked.

36. SYNOVIAL MEMBRANE
• It lines the lateral and
medial parts of the capsule.
• Anteriorly :
• It forms the supra patellar
bursa.
• It is attached to the inter
condylar area of the tibia
and to the lateral and
medial borders of the
patella.

37. SYNOVIAL MEMBRANE
• It is reflected backward
from the posterior surface
of the ligamentum
patellae to form the
Infrapatellar fold.
• The free borders of the
fold are the Alar folds.
• The space between these
folds contains fat
(Infrapatellar pad of fat).

38. SYNOVIAL MEMBRANE
• Posteriorly :
• It Passes out to
surround the cruciate
ligaments.
• It is continuous with the
surface layer of the
menisci.
• It covers the tendon of
popliteus and forms a
bursa around it
(popliteal bursa).
• It forms the
semimembranosus
bursa.

39. Bursa
• 20 + associated with
the knee
• Most important
• Subcutaneous
prepatellar
• Subcutaneous
infrapatellar
• Deep infrapatellar
• Anserine bursa
• Bursa deep to iliotibial
band
• Inferior subtendinous
bursa of biceps

40. ANTERIOR BURSAE
• They are four :
• 1. Suprapatellar :
• It is 3 fingerbreadths above the
patella.
• Always continuous with the
joint cavity.
• Held in position by the
articularis genus muscle.
• Accumulation of fluid in the
joint causes excees fluid in the
bursa leading to floating
patella.

41. ANTERIOR BURSAE
• 2. Prepatellar
• If enlarged it causes (House
Maid’s) bursa.

42. Bursa

43. ANTERIOR BURSAE
• 3.Superficial
Infrapatellar.
(PARSON’S bursa
• 4.Deep Infrapatellar.

44. POSTERIOR BURSAE (6)
• 1. POPLITEAL
• Always continuous with
the joint cavity.
• 2.SEMIMEMBRANOSU
• Usually communicates
with the joint cavity.
• 3 & 4. GASTROCNEMIUS
• Around sartorius,gracilis
and semitendinosus.

45. MOVEMENTS
• 1. FLEXION
• Hamstrings( supplied
by the sciatic nerve).
• Assisted by sartorius,
popliteus and gracilis.
– Checked by back of calf
in contact with the back
of the thigh.

46. MOVEMENTS
– 2. EXTENSION
– Quadriceps Femoris
(supplied by the femoral
nerve.)
– Limited by tension of the
cruciate and collateral
ligaments.

47. Knee Motion
• The long articulating surface of the femoral condyles
is about twice the length of the tibial condyles
• Therefore the activity of flexion and extension can
not be a pure hinge motion or simple rolling of one
bone over the other
• Instead the condyles execute both rolling and sliding
motions
• Rolling is predominant at the initiation of flexion and
sliding occurs more at the end of flexion

48. UNLOCKING
• At the commencement of Flexion
of the extended knee.
• Aim :
• To slack the ligaments especially
the cruciate.
• FEMUR: Lateral rotation (the foot
is on the ground)
• TIBIA: Medial rotation.
• Muscle: POPLITEUS

49. LOCKING • The joint assumes the position
of full extension.
• It becomes a rigid structure.
• The menisci are compressed
between the tibial and femoral
condyles.
• Tightening of all the major
ligaments.
• The femur is medially rotated
on the tibia.

50. NERVE SUPPLY
• Femoral.
• Obturator.
• Sciatic.
• Common peroneal.
• Tibial.

51. RELATIONS
• Posterior :
• Boundaries and
contents of Popliteal
Fossa.
• Medial :
• SGS muscles.
• Lateral :
• Biceps femoris and
common peroneal
nerve.

52. STABILITY
• 1. Muscles :
• QUADRICEPS particularly
the inferior fibers of the
vasti lateralis and medialis.
• Many sport injuries can be
preventable through
appropriate training and
conditioning of the muscle.

53. STABILITY
• 2. Ligaments :
• The knee joint can function
well following a ligamentous
strain if the quadriceps is
intact.

54. INJURY OF THE JOINT
• TRIAD OF INJURY
• 1. Medial collateral
ligament.
• 2. Medial meniscus.
• 3. Anterior cruciate
ligament.
• The joint becomes swollen
because it is filled with
blood (hemarthrosis).

55. ANTERIOR CRUCIATE INJURY
• Tear of the anterior
cruciate ligament is
more common than
the posterior.
• The tibia can be
pulled excessively
forward on the femur

56. POSTERIOR CRUCIATE INJURY
• The tibia can be pulled
excessively backward
on the femur.

57. INJURY OF THE CRUCIATE LIGAMENTS
• Management :
• Knee is kept immobilized in
slight flexion.
• Active physiotherapy of the
quadriceps femoris at
once.
• Operative repair (incase of
torn of the capsule and
collateral ligaments).

58. Q Angle
• An angle found by drawing a line from ASIS to middle
of patella and a second line from mid patella to tibial
tuberosity
– Represents efficiency of Quads
– Most efficient = 10 degrees
– Males range from 10-14
– Females from 15-17
– Represents the valgus stress acting on knee and, if
excessive, can cause patello femoral problems
• Great than 17 degrees considered excessive, called
genu valgum or knock knees
• Very small angle causes genu varum

59. “Q” Angle
• Line from ASIS to midpoint
of the patella
• Line from Tibial tubercle
to midpoint of the patella

60. “Q” Angle
• Normal
– about 15°
• Males vs. Females
– wider pelvis

65. Cruciate Ligaments
• Major stabilizing
ligaments in the knee
• Anterior Cruciate
Ligament (ACL)-prevents
the tibia from sliding out
in front of the femur
• Injuries caused by
hyperflexion, internal
rotation, hyperextension