Transcript The Knee Complex

Chapter 18
The Knee Complex
Overview


The knee joint complex is extremely
elaborate and includes three articulating
surfaces, which form two distinct joints
contained within a single joint capsule: the
patellofemoral and tibiofemoral joint
Given the frequency of knee injuries and the
intricate nature of this joint complex,
clinicians caring for knee injuries must have
an extensive knowledge base
Anatomy

The tibiofemoral joint
– The tibiofemoral joint consists of the
distal end of the femur and the proximal
end of the tibia
– The distal aspect of the femur is
composed of two femoral condyles that
are separated by an intercondylar notch

The intercondylar notch serves to accept the
anterior cruciate ligament (ACL) and the
posterior cruciate ligament (PCL)
Anatomy

Distal femur
– The femoral condyles project posteriorly from
the femoral shaft
– The smaller lateral femoral condyle is ballshaped and faces outward, while the ellipticalshaped medial femoral condyle faces inward
– The lateral epicondyle serves as the origin for
the lateral head of the gastrocnemius, and the
lateral collateral ligament (LCL)
– The medial condyle serves as the insertion site
for the adductor magnus, and the medial
collateral ligament (MCL)
Anatomy

Femoral condyles
– The anterior-posterior length of the
medial femoral condyle is greater than its
lateral counterpart by about 1.7 cm
– The length of the articular surface of the
medial femoral condyle is longer than the
length of the lateral femoral condyle
Anatomy

Proximal tibia
– The proximal tibia is composed of two plateaus
separated by the intercondylar eminence,
including the medial and lateral tibial spines
– The tibial plateaus are concave in a mediallateral direction
– In the anterior-posterior direction, the medial
tibial plateau is also concave, while the lateral is
convex, producing more asymmetry, and an
increase in lateral mobility
– The medial plateau has an approximately 50%
greater surface area than the lateral plateau,
and its articular surface is 3 times thicker
Anatomy

Patellofemoral Joint
– The patellofemoral joint is a complex
articulation, dependent on both dynamic and
static restraints for its function and stability
– The patella is a very hard triangular-shaped
bone, situated in the intercondylar notch, and
embedded in the tendon of the quadriceps
femoris muscle above, and the patella tendon
below
– The posterior surface of the patella can include
up to seven facets, with three on the medial and
lateral surfaces
Anatomy

The patellofemoral joint functions to:
– Provide an articulation with low friction
– Protect the distal aspect of the femur from
trauma, and the quadriceps from attritional wear
– Improve the cosmetic appearance of the knee
– Improve the moment arm of the quadriceps
– Decrease the amount of anterior-posterior
tibiofemoral shear stress placed on the knee
joint
Anatomy

The knee joint capsule
– is composed of a thin, strong fibrous membrane
– is the largest synovial capsule in the body
– A synovial membrane lines the inner portion of
the knee joint capsule. By lining the joint
capsule, the synovial membrane excludes the
cruciate ligaments from the interior portion of
the knee joint, making them extrasynovial yet
intra-articular
Anatomy

The proximal tibiofibular joint
– An almost plane joint with a slight
convexity on the oval tibial facet and a
slight concavity of the fibular head
– Has more motion than its distal partner
Anatomy

Ligaments
– The static stability of the knee joint
complex depends on four major knee
ligaments, which provide a primary
restraint to abnormal knee motion
Anterior cruciate
 Posterior cruciate
 Medial collateral
 Lateral collateral

Anatomy

The cruciate ligaments
– Are intra-articular/extra synovial because
of the posterior invagination of the
synovial membrane
– Are different from those of other joints, in
that, they restrict normal motion, rather
than restrict abnormal motion
Anatomy

Both the anterior cruciate ligament
(ACL) and the posterior cruciate
ligament (PCL) are each named
according to their attachment sites on
the tibia
Anatomy

The anterior cruciate ligament
– One of the most important ligaments to
knee stability
– Serves as a primary restraint to anterior
translation of the tibia relative to the
femur, and a secondary restraint to both
internal and external rotation in the nonweight bearing knee
Anatomy

The posterior cruciate ligament
– Provides 90-95% of the total restraint to
posterior translation of the tibia on the
femur, with the remainder being provided
by the collateral ligaments, posterior
portion of the medial and lateral capsules,
and the popliteus tendon
Anatomy

The medial collateral ligament (MCL)
– The anterior fibers of this ligament are
taut in flexion, and can be palpated easily
in this position
– The posterior fibers, which are taut in
extension, blend intimately with the
capsule and with the medial border of the
medial meniscus, making them difficult to
palpate
Anatomy

The lateral collateral ligament (LCL)
– The main function of the LCL is to resist
varus forces

It offers the majority of the varus restraint at
25° of knee flexion, and in full extension
Anatomy

Secondary restraints include:
– The structures in the posterior-lateral and
posterior-medial corners of the knee
– The hamstrings and quadriceps
– The patellar ligament, oblique popliteal
ligaments, and the fabella
Anatomy

Menisci
– The crescent-shaped lateral and medial
menisci, attached on top of the tibial
plateaus, are pieces of fibrocartilage
material that lie between the articular
cartilage of the femur and the tibia
Anatomy

Medial meniscus
– Semi-lunar or C-shaped
– Larger and thicker than its lateral
counterpart
– Sits in the concave medial tibial plateau
– Wider posteriorly than anteriorly
Anatomy

Lateral meniscus
– Rounder O-shaped
– Sits atop the convex lateral tibial plateau
– Smaller and thinner, than its medial
counterpart
– More mobile than its medial counterpart
– Two mensicofemoral ligaments, the
ligaments of Humphrey and Wrisberg
attach to the lateral meniscus
Anatomy

Menisci Function
– The menisci assist in a number of
functions including load transmission,
shock absorption, joint lubrication, joint
stability and the guiding of movements
Anatomy

Bursae
– There are a number of bursae situated in
the soft tissues around the knee joint
– The bursae serve to reduce friction, and
to cushion the movement of one body
part over another
Anatomy

Plica
– Synovial plica represents a remnant of
the three separate cavities in the synovial
mesenchyme of the developing knee
Anatomy

Retinacula
– Formed from structures in the first and
second layers of the knee joint
– The retinacula can be subdivided into the
medial and the lateral retinacula for
clinical examination and intervention
purposes
Anatomy

Muscles
– The major muscles that act on the knee
joint complex are the quadriceps, the
hamstrings (semimembranosus,
semitendinosus, and the biceps femoris),
the gastrocnemius, the popliteus, and the
hip adductors
Anatomy

Vascular supply
– The major blood supply to this area
comes from the femoral, popliteal, and
genicular arteries
Anatomy

Neurology
– Femoral nerve

Saphenous nerve
– Sciatic nerve
Common peroneal
 Tibial

Biomechanics

The tibiofemoral joint
– The tibiofemoral joint, or knee joint, is a
ginglymoid, or modified hinge joint, which has
six degrees of freedom
– The bony configuration of the knee joint
complex is geometrically incongruous and lends
little inherent stability to the joint
– Joint stability is therefore dependent upon the
static restraints of the joint capsule, ligaments,
and menisci, and the dynamic restraints of the
quadriceps, hamstrings, and gastrocnemius
Biomechanics

Patellofemoral joint
– To assist in the control of the forces
around the patellofemoral joint, there are
a number of static and dynamic restraints
Biomechanics

The Quadriceps (‘Q’) angle
– Can be described as the angle formed by the
bisection of two lines, one line drawn from the
anterior superior iliac spine (ASIS) to the center
of the patella, and the other line drawn from the
center of the patella to the tibial tubercle
– The most common ranges cited are 8-14° for
males and 15-17° for females
– Angles of greater than 20° are considered
abnormal and may be indicative of potential
displacement of the patella
Biomechanics

Patella-Femur Contact and Loading
– The amount of contact between the
patella and the femur appears to vary
according to a number of factors
including:
The
 The
 The
 The

angle of knee flexion
location of contact
surface area of contact
patellofemoral joint reaction force
Biomechanics

Patella Stability
– Patella stability is dependent on 2 factors:
Static restraints
 Dynamic restraints

Biomechanics

Patellar Tracking
– In the normal knee, the patella glides in a
sinuous path inferiorly and superiorly during
flexion and extension respectively, covering a
distance of 5-7 cm with respect to the femur
– One proposed mechanism for abnormal patellar
tracking is an imbalance in the activity of the of
the vastus medialis obliquus (VMO) relative to
the vastus lateralis (VL)
Biomechanics

Open and Closed Kinetic Chain Activities
– An understanding of the forces generated and
the muscle activity employed by different
exercises is essential for determining how to
achieve optimal balance of muscle force,
ligament tension, and joint compression
– Whether the motion occurring at the knee joint
complex occurs as a closed or open kinetic chain
has implications on the biomechanics and the
joint compressive forces induced
Examination

History
– The diagnosis of tibiofemoral and
patellofemoral joint disorders can often
be made on the history and physical
examination alone

With the larger number of specific tests
available for the knee joint complex, it is
tempting to overlook the important role of the
history, which can detail both the chronology,
and mechanism, of events
Examination

History
– The mechanism of the injury is one of the most
important aids in making a diagnosis
– The position of the joint at the time of the
traumatic force dictates which anatomic
structures are at risk for injury
– The primary mechanisms of injury in the knee
are direct trauma, a varus or valgus force (with
or without rotation), hyperextension, flexion with
posterior translation, a twisting force, and
overuse
Examination

History
– There is a significant temptation to cut corners
with a patient who presents with anterior knee
pain, and to proceed directly to the diagnosis of
patellofemoral pain
– Particular activities can help with differential
diagnosis

Complaints of pain that occur when a patient arises
from a seated position, negotiates stairs, or squats, are
associated with patellofemoral dysfunction
Examination

Systems Review
– Knee pain can be referred to the knee
from the lumbosacral region (L 3 to S 2
segments), or from the hip
Examination

Observation
– The observation component of the
examination begins as the clinician meets
the patient and ends as the patient is
leaving
– This informal observation should occur at
every visit
Examination

Active Range of Motion with Passive Over
pressure
– Normal knee motion has been described as 0° of
extension to 135° of flexion, although
hyperextension is frequently present to varying
degrees
– Passive movements, as elsewhere, can
determine the amount of motion and the endfeel
– Resisted testing is performed to provide the
clinician with information about the integrity of
the neuromuscular unit, and to highlight the
presence of muscle strains
Examination

Palpation
– For palpation to be reliable, the clinician
must have a sound knowledge of surface
anatomy, and the results from the
palpation exam should be correlated with
other findings
Examination

Functional Tests
– Functional outcome following knee injury
must consider the patient’s perspective,
and not just objective measurements of
instability
– Functional motion requirements of the
knee vary according to the specific task
– A number of commonly used rating scales
can be used to assess knee function
Examination

Special Tests
– Special tests are merely confirmatory
tests and should not be used alone to
form a diagnosis
– The results from these tests are used in
conjunction with the other clinical
findings to help guide the clinician
– To assure accuracy with these tests, both
sides should be tested for comparison
Intervention

Acute Phase
– The goals during the acute phase are:
Reduce pain and swelling
 Control inflammation
 Regain range of motion
 Minimize muscle atrophy/weakness
 Attain early neuromuscular control
 Maintain general fitness

Intervention

Functional Phase
– The goals for this phase include:
Attain full range of pain free motion
 Restore normal joint kinematics
 Improve muscle strength
 Improve neuromuscular control
 Restore normal muscle force couple
relationships
