PMR PG Teaching

1. APPLIED ANATOMY
OF KNEE
-Dr Anurag
Ranga

2. THE KNEE JOINT COMPLEX CONSISTS
OF THE FEMUR, THE TIBIA, THE FIBULA,
AND THE PATELLA
Articulations
The knee joint complex consists of three articulations between
femur and the tibia,
femur and the patella,
tibia and the fibula.

3. Characterized by two large condyles, which articulate with
the proximal head of the tibia.
The condyles are separated posteriorly by an
intercondylar fossa and are joined anteriorly where they
articulate with the patella.
The surfaces of the condyles that articulate with the tibia
are rounded posteriorly and become flatter inferiorly.
The walls of the intercondylar fossa bear two facets for the
superior attachment of the cruciate ligaments, which
stabilize the knee joint.
The wall formed by the lateral surface of the medial
condyle has a large oval facet, which covers most of the
inferior half of the wall, for attachment of the proximal end
of the posterior cruciate ligament;
The distal end of femur

4. The wall formed by the medial surface of the lateral
condyle has a posterosuperior smaller oval facet for
attachment of the proximal end of the anterior
cruciate ligament
Epicondyles, for the attachment of collateral
ligaments of the knee joint, are bony elevations on
the nonarticular outer surfaces of the condyles.
Two facets separated by a groove are just posterior
to the lateral epicondyle: the upper facet is for
attachment of the lateral head of the gastrocnemius
muscle; the inferior facet is for attachment of the
popliteus muscle.
The medial epicondyle is a rounded eminence on
the medial surface of the medial condyle. Just
posterosuperior to the medial epicondyle is the
adductor tubercle.

6. PR0XIMAL END OF TIBIA
The proximal end of the tibia is expanded in the
transverse plane for weight bearing and consists of a
medial condyle and a lateral condyle, which are both
flattened in the horizontal plane and overhang the shaft.
The superior surfaces of the medial and lateral condyles
are articular and separated by an intercondylar region,
which contains sites of attachment for strong ligaments
(cruciate ligaments) and interarticular cartilages (menisci)
of the knee joint.

7. The articular surfaces of the medial and lateral
condyles and the intercondylar region together form
a "tibial plateau," which articulates with and is
anchored to the distal end of the femur. Inferior to
the condyles on the proximal part of the shaft is a
large tibial tuberosity and roughenings for muscle
and ligament attachments.
The medial condyle is larger than the lateral condyle
and is better supported over the shaft of the tibia. Its
superior surface is oval for articulation with the
medial condyle of the femur. The articular surface
extends laterally onto the side of the raised medial
intercondylar tubercle
The superior surface of the lateral condyle is circular
and articulates above with the lateral condyle of the
femur.

8. The medial edge of this surface extends onto the
side of the lateral intercondylar tubercle
The superior articular surfaces of both the lateral
and medial condyles are concave particularly
centrally. The outer margins of the surfaces are
flatter and are the regions in contact with the
interarticular discs (menisci) of fibrocartilage in
the knee joint.
The intercondylar region of the tibial plateau lies
between the articular surfaces of the medial and
lateral condyles. It is narrow centrally where it is
raised to form the intercondylar eminence, the
sides of which are elevated further to form
medial and lateral intercondylar tubercles.

10. The intercondylar region bears six distinct facets for
the attachment of menisci and cruciate ligaments.
The anterior intercondylar area widens anteriorly
and bears three facets:
the most anterior facet is for attachment of the
anterior end (horn) of the medial meniscus;
immediately posterior to the most anterior facet is
a facet for the attachment of the anterior cruciate
ligament;
a small facet for the attachment of the anterior end
(horn) of the lateral meniscus is just lateral to the
site of attachment of the anterior cruciate ligament.

11. The posterior intercondylar area also bears three
attachment facets: the most anterior is for
attachment of the posterior horn of the lateral
meniscus; posteromedial to the most anterior facet
is the site of attachment for the posterior horn of the
medial meniscus; behind the site of attachment for
the posterior horn of the medial meniscus is a large
facet for the attachment of the posterior cruciate
ligament.

13. PROXIMAL END OF FIBULA
The fibula is the lateral bone of the leg and does not
take part in formation of the knee joint or in
weightbearing. It is much smaller than the tibia and
has a small proximal head, a narrow neck, and a
delicate shaft, which ends as the lateral malleolus at
the ankle.
The head of the fibula is a globe-shaped expansion at
the proximal end of the fibula. A circular facet on the
superomedial surface is for articulation above with a
similar facet on the inferior aspect of the lateral
condyle of the tibia. Just posterolateral to this facet,
the bone projects superiorly as a blunt apex (styloid
process).

15. PATELLA
The patella (knee cap) is the largest sesamoid bone (a
bone formed within the tendon of a muscle) in the body and
is formed within the tendon of the quadriceps femoris
muscle as it crosses anterior to the knee joint to insert on
the tibia.
The patella is triangular.
Its apex is pointed inferiorly for attachment to the patellar
ligament, which connects the patella to the tibia
Its base is broad and thick for the attachment of the
quadriceps femoris muscle from above;
Its posterior surface articulates with the femur and has
medial and lateral facets, which slope away from a raised
smooth ridge-the lateral facet is larger than the medial facet
for articulation with the larger corresponding surface on the
lateral condyle of the femur.

20. The following is a list of knee actions and the muscles that
initiate them.
•Knee flexion is executed by the biceps femoris,
semitendinosus, semimembranosus, gracilis, sartorius,
gastrocnemius, popliteus, and plantaris muscles.
• Knee extension is executed by the quadriceps muscle of
the thigh, consisting of three vasti—the vastus medialis,
vastus lateralis, and vastus intermedius—and by the rectus
femoris.
External rotation of the tibia is controlled by the biceps
femoris. The bony anatomy also produces external tibial
rotation as the knee moves into extension.
Internal rotation is accomplished by the popliteal,
semitendinosus, semimembranosus, sartorius, and gracilis
muscles. Rotation of the tibia is limited and can occur only
when the knee is in a flexed position.

21. JOINT CAPSULE
The articular surfaces of the knee joint are completely
enveloped by the largest joint capsule in the body
Anteriorly, the joint capsule extends upward underneath
the patella to form the suprapatellar pouch.
The inferior portion contains the infrapatellar fat pad
and the infrapatellar bursa.
Medially, a thickened section of the capsule forms the
deep portion of the medial collateral ligament.
Posteriorly, the capsule forms two pouches that cover
the femoral condyles and the tibial plateau.

22. Synovial membrane
The synovial membrane of the knee joint attaches to
the margins of the articular surfaces and to the
superior and inferior outer margins of the menisci .
Posteriorly, the synovial membrane reflects off the
fibrous membrane of the joint capsule on either side of
the posterior cruciate ligament and loops forward
around both ligaments thereby excluding them from
the articular cavity.
Anteriorly, the synovial membrane is separated from
the patellar ligament by an infrapatellar fat pad.
In addition, the synovial membrane covering the lower
part of the infrapatellar fat pad is raised into a sharp
midline fold directed posteriorly (the infrapatellar
synovial fold), which attaches to the margin of the
intercondylar fossa of the femur.

23. The synovial membrane of the knee joint forms
pouches in two locations to provide low friction
surfaces for the movement of tendons associated with
the joint:
the smallest of these expansions is the subpopliteal
recess which extends posterolaterally from the
articular cavity and lies between the lateral meniscus
and the tendon of the popliteus muscle, which passes
through the joint capsule;
the second expansion is the suprapatellar bursa a
large bursa that is a continuation of the articular cavity
superiorly between the distal end of the shaft of femur
and Thigh Synovial membrane of the knee joint and
associated bursae.

25. Locking Mechanism
When standing, the knee joint is locked into position,
thereby reducing the amount of muscle work needed to
maintain the standing position.
One component of the locking mechanism is a change in
the shape and size of the femoral surfaces that articulate
with the tibia:
in flexion, the surfaces are the curved and rounded
areas on the posterior aspects of the femoral condyles;
as the knee is extended, the surfaces move to the broad
and flat areas on the inferior aspects of the femoral
condyles.

26. Consequently the joint surfaces become larger and more
stable in extension.
Another component of the locking mechanism is medial
rotation of the femur on the tibia during extension.
Medial rotation and full extension tightens all the
associated ligaments.
Another feature that keeps the knee extended when
standing is that the body's center of gravity is positioned
along a vertical line that passes anterior to the knee joint.

29. STABILIZING LIGAMENTS
The major stabilizing ligaments of the knee are the cruciate
ligaments, the collateral ligaments, and the capsular
ligaments.
The cruciate ligaments account for a considerable amount
of knee stability. They are two ligamentous bands that
cross one another within the joint capsule of the knee.
The anterior cruciate ligament (ACL) attaches below and
in front of the tibia; then, passing backward, it attaches
laterally to the inner surface of the lateral condyle.
The posterior cruciate ligament (PCL), the stronger of
the two, crosses from the back of the tibia in an upward,
forward, and medial direction and attaches to the anterior
portion of the lateral surface of the medial condyle of the

31. Anterior Cruciate Ligament comprises three twisted
bands: the anteromedial, intermediate, and
posterolateral bands.
In general, the anterior cruciate ligament prevents the
femur from moving posteriorly during weight bearing
and limits anterior translation of the tibia in non–weight
bearing. It also stabilizes the tibia against excessive
internal rotation and serves as a secondary restraint for
valgus or varus stress with collateral ligament damage.
When the knee is fully extended, the posterolateral
section of the cruciate ligament is most tight.
In flexion the posterolateral fibers loosen and the
anteromedial fibers tighten. The anterior cruciate
ligament works in conjunction with the thigh muscles,
especially the hamstring muscle group, to stabilize the
knee joint.

32. Posterior Cruciate Ligament Some portion of the
posterior cruciate ligament is taut throughout the full
range of motion. In general, the posterior cruciate
ligament resists internal rotation of the tibia, prevents
hyperextension of the knee, limits anterior translation
of the femur during weight bearing, and limits
posterior translation of the tibia in non–weight
bearing.
Capsular and Collateral Ligaments Additional
stabilization of the knee is provided by the capsular
and collateral ligaments. Besides providing stability,
they also direct movement in a correct path. Although
they move in synchrony, they are divided into the
medial and lateral complexes.

33. Medial Collateral Ligament The superficial position of
the medial (tibial) collateral ligament (MCL) is separate
from the deeper capsular ligament at the joint line.
It attaches above the joint line on the medial epicondyle of
the femur and below on the tibia, just beneath the
attachment of the pes anserinus.
The posterior aspect of the ligament blends into the deep
posterior capsular ligament and semimembranous muscle.
Fibers of the semimembranous muscle go through the
capsule and attach to the posterior aspect of the medial
meniscus, pulling it backward during knee flexion.
Its major purpose is to prevent the knee from valgus and
external rotating forces.

35. Lateral Collateral Ligament and Related Structures
The lateral (fibular) collateral ligament (LCL) is a round,
fibrous cord that is about the size of a pencil. It is
attached to the lateral epicondyle of the femur and to
the head of the fibula. The lateral collateral ligament is
taut during knee extension but relaxed during flexion.
The arcuate ligament is formed by a thickening of the
posterior articular capsule. Its posterior aspect attaches
to the fascia of the popliteal muscle and the posterior
horn of the lateral meniscus.
Other structures that stabilize the knee laterally are the
iliotibial band, popliteus muscle, and biceps femoris.

36. BURSAE
A bursa is composed of pieces of synovial tissue
separated by a thin fi lm of fluid. The function of a
bursa is to reduce the friction between anatomical
structures.
Bursae are found between muscle and bone, tendon
and bone, tendon and ligament, and so forth.
As many as two dozen bursae have been identified
around the knee joint. The suprapatellar, prepatellar,
infrapatellar, pretibial, and gastrocnemius bursae
are perhaps the most commonly injured about the
knee joint.

39. Sciatic nerve
The sciatic nerve is a branch of the lumbosacral plexus
(spinal cord segments L4-S3) and descends into the
posterior compartment of thigh from the gluteal region ).
In the posterior compartment of thigh, the sciatic nerve
lies on the adductor magnus muscle and is crossed by
the long head of biceps femoris muscle.
Proximal to the knee, the sciatic nerve divides into its
two terminal branches: the tibial nerve and the
common fibular nerve.
These nerves travel vertically down the thigh and enter
the popliteal fossa posterior to the knee. Here, they meet
the popliteal artery and vein.
Nerve Supply

40. The tibial nerve innervates most of the hamstrings and
the gastrocnemius.
The common peroneal nerve innervates the short head
of the biceps femoris and then courses through the
popliteal fossa and wraps around the proximal head of
the fibula.
Because the peroneal nerve is exposed at the head of
the fi bula, contusion of the nerve can cause distal
sensory and motor deficits.

42. Leg Alignment Deviations That May Predispose to
Injury Four major leg deviations could adversely affect the
knee and patellofemoral joints: patellar malalignment,
genu valgum (knockknees),
Genu varum (bowlegs),
and genu recurvatum(hyperextended knees).
Patellar malalignment In patella alta, the patella sets in a
more superior position than normal when the patient is
standing. The ratio of patellar tendon length to the height of
the patella is greater than the normal 1:1 ratio. In patella
alta, the length of the patellar tendon is 20 percent greater
than the height of the patella.
In patella baja ,the patella sets in a more inferior position
than normal and the ratio of patellar tendon length to the
height of the patella is less than the normal 1:1 ratio.

43. Medial Collateral Ligament Sprain
Etiology Most knee sprains affect the MCL from
either a direct blow from the lateral side in a medial
direction (valgus force) or from lateral tibial rotation.

44. Lateral Collateral Ligament Sprain Sprain of the lateral
collateral ligament of the knee is much less prevalent than
sprain of the medial collateral ligament.
Etiology The force required to tear this ligament is varus,
often with the tibia internally rotated

45. Anterior Cruciate Ligament Sprain
Etiology The anterior cruciate ligament sprain is generally
considered to be the most serious ligament injury in the
knee.
The ACL is most vulnerable to injury when the tibia is
externally rotated and the knee is in a valgus position. The
ACL can sustain injury from a direct blow to the knee or
from a noncontact single-plane force.

46. Posterior Cruciate Ligament Sprain The PCL has been
called the most important ligament in the knee, providing a
central axis for rotation. The PCL provides about 95
percent of the total restraining force to straight posterior
displacement of the tibia.
Etiology The PCL is most at risk when the knee is flexed
to 90 degrees. A fall with full weight on the anterior aspect
of the bent knee with the foot in plantar flexion or receipt of
a hard blow to the front of the bent knee can tear the PCL

47. Meniscal Lesions
The medial meniscus has a much higher incidence of
injury than does the lateral meniscus The lateral meniscus
does not attach to the capsular ligament and is more
mobile during knee movement. Because of the attachment
to the medial structures, the medial meniscus is prone to
disruption from valgus and torsional forces.
Etiology A valgus force can adduct the knee, often
tearing and stretching the medial collateral ligament;
meanwhile, its fibers twist the medial meniscus outward.
Repeated mild sprains reduce the strength of the knee to
a state favourable for a cartilaginous tear by lessening its
normal ligamentous stability.

48. The most common mechanism is weight bearing
combined with a rotary force while the knee is extended
or flexed. If an individual makes a cutting motion while
running, it can distort the medial meniscus.
Stretching of the anterior and posterior horns of the
meniscus can produce a verticallongitudinal, or “bucket-
handle” tear. Another way that a longitudinal tear occurs
is if the knee is forcefully extended from a flexed position
while the femur is internally rotated.

49. During extension, the medial meniscus is suddenly
pulled back, causing the tear. In contrast, the lateral
meniscus can sustain an oblique tear by a forceful knee
extension with the femur externally rotated. These
oblique tears are sometimes referred to as “parrot beak”
tears and occur in the inner periphery of the meniscus.
A large number of medial meniscus lesions are the
outcome of a sudden, strong internal rotation of the
femur with a partially flexed knee while the foot is firmly
planted.
The force of this action pulls the meniscus out of its
normal bed and pinches it between the femoral condyles.
Meniscal lesions can be longitudinal, oblique, or
transverse. Because of the blood supply of a meniscus,
tears in the outer one-third of the meniscus may heal
over time if stress in the area is a minimized.

50. Valgus force → medial collateral ligament rupture. If the
force continues- medial meniscus injury and with further
force ACL rupture
Varus force → lateral collateral ligament injury
Hyperextension force → ACL injury
Fall on to flexed knee/ dashboard injury → PCL injury
Forceful internal rotation → lateral meniscus injury
Forceful external rotation → medial meniscus injury
Hyperflexion (squatting) → meniscus injury (posterior
horn)

51. INTRA ARTICULAR
INJECTION

52. Bursitis Bursitis in the knee can be acute, chronic, or
recurrent. Although any one of the numerous knee
bursae can become infl amed, anteriorly the prepatellar,
deep infrapatellar, and suprapatellar bursae have the
highest incidence of irritation.
Etiology The prepatellar bursa often becomes inflamed
from placing pressure on the front of the knee while
kneeling, and the deep infrapatellar bursa becomes
irritated from overuse of the patellar tendon.

53. Symptoms and signs Prepatellar bursitis results in
localized swelling above the knee that is ballotable.
Swelling is not intraarticular, and there may be some
redness and increased temperature.
Swelling in the popliteal fossa could be a sign of a
Baker’s cyst. A Baker’s cyst is associated with the
semimembranosus bursa and occurs under the
medial head of the gastrocnemius muscle. It is
connected directly to the joint, and it swells because
of a problem in the joint, not because of bursitis.
A Baker’s cyst is commonly painless, causing no
discomfort or disability. Some inflamed bursae may
be painful and disabling because of the swelling and
should be treated accordingly.

55. LOCALIZED SWELLING
Anterior aspect of the knee
Prepatellar bursitis
Infrapatellar bursitis
Lateral aspect of the knee
Lateral meniscal cyst
Posteromedially
Semimembranosus bursitis
Posteriorly
Baker’s cyst
Popliteal aneurysm

56. 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
Males range from 10-14
Females from 15-17
Great than 17 degrees knock knees
Very small angle causes genu varum

57. References
• Clinical Neuroanatomy, Snell’s
• Gray’s Anatomy
• Snell’s Anatomy