Download 4. Joints and Ligaments

Joints and Articulations
Arthrology
Joints And Their Classification
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A joint, or articulation, is any point at
which two bones meet, regardless of
whether they are movable at that point
The science of joint structure, function,
and dysfunction is called arthrology
The study of musculoskeletal movement is
kinesiology
Joints And Their Classification

Kinesiology is a branch of biomechanics,
which deals with a broad range of motions
and mechanical processes in the body,
including the physics of blood circulation,
respiration, and hearing.
About Joints
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Tendons
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Ligaments
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bind a muscle to bone
bind bone to bone
Both are dense regular connective tissue
Muscles act at a joint, and have:
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Origin (the part that does not move)
Insertion (the part that moves)
action
Characterizing Joints
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Joints can be characterized two different ways:
1) What type of movement does the joint allow?
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No movement, limited movement, free movement
2) What tissue joins the bones?
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Fibrous Joints
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Fibrous connective tissue (eg. suture, ligament, tooth)
Cartilaginous Joints
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Hyaline cartilage (eg. epiphyseal plate, costal cartilage)
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Fibrocartilage (eg. pubic symphysis)
Synovial Joints (Hyaline cartilage plus a capsule)
Characterizing Joints by the
Types of Movement
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Synarthrotic
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Amphiarthrotic
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immoveable, allows no movement
allows only limited movement
Diarthrotic
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freely moveable
Warning: Don’t go any further until you memorize these three
types of movements, or you will get lost!
Characterizing Joints by the
Types of Tissue Between Bones
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Fibrous Joints
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Fibrous connective tissue (eg. suture, ligament, tooth)
Cartilaginous Joints
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Hyaline cartilage (eg. epiphyseal plate, costal cartilage)
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Fibrocartilage (eg. pubic symphysis)
Synovial Joints (Hyaline cartilage plus a capsule)
Warning: Don’t get fibrous connective tissue mixed up
with fibrocartilage. Connective tissue is mostly
collagen secreted by fibroblast cells. Connective tissue
is not made of cells, unlike fibrocartilage. There are no
nuclei seen in connective tissue.
Characterizing Joints by the
Types of Tissue Between Bones
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Fibrous Joints
 These are made of dense regular fibrous
connective tissue
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Examples are sutures, ligaments, tooth
sockets)
Suture (dense fibrous C. T. between bony plates)
Syndesmosis (these are the ligaments, which are
also dense fibrous connective tissue )
Gomphosis (tooth socket; a type of ligament)
Movement Allowed by the
Different Types of Fibrous Joints
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Sutures (immoveable = synarthrotic)
Gomphoses (immoveable = synarthrotic)
Syndesmoses (slightly moveable = amphiarthrotic)
Summary of Fibrous Joints
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A fibrous joint is two bones joined by
dense fibrous connective tissue.
No joint cavity
Some fibrous joints are immoveable
(sutures and gomphoses) and some are
slightly moveable (syndesmoses, which are
the ligaments)
Suture
•In sutures and
gomphoses, the
fibers are very
short and allow
for little or no
movement
Syndesmosis (ligaments)
•In syndesmoses, the
fibers are longer and
the attached bones
are more movable:
ligament attaches!
Gomphosis (special ligament)
The
periodontal
ligament is
the only
example of a
gomphosis
That’s
enough on
fibrous joints.
Now we will
go on to
cartilaginous
joints.
Cartilaginous Joints
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A cartilaginous joint is two bones joined by cartilage.
The cartilage is either fibrocartilage (a symphysis joint)
or hyaline cartilage (a synchondrosis).
Hyaline cartilage joints (synchondroses) are synarthrotic
(immovable).
 Examples are epiphyseal plates and costal cartilages
Fibrocartilage joints (symphyses) are amphiarthrotic
(slightly moveable).
 Examples are the pubic symphysis and intervertebral
discs.
Hyaline Cartilage Joints
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Hyaline cartilage joints (synchondroses)
are synarthrotic (immovable).
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Examples are epiphyseal plates and costal
cartilages
Synchondrosis
Epiphyseal
plate
Costal
cartilages
A synchondrosis
is a joint in
which the bones
are bound by
hyaline cartilage
(A synchondrosis is
synarthrotic: not
moveable)
A synchondrosis
is a synarthrosis
Fibrocartilage Joints
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Fibrocartilage joints (symphyses) are
amphiarthrotic (slightly moveable).
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Examples are the pubic symphysis and
intervertebral discs.
Fibrocartilage
Joints
Symphysis
In a symphysis, two
bones are joined by
fibrocartilage (A symphysis
is amphiarthrotic: slightly
moveable)
Warning
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Remember, don’t confuse fibrous connective tissue
with fibrocartilage!
 Joints are classified as being either fibrous (fibrous
connective tissue) or cartilaginous (hyaline or
fibrocartilage).
Also, don’t confuse hyaline joints (which have no
capsule and are not moveable) with synovial joints,
which have hyaline cartilage, but also have a synovial
capsule and are very moveable).
Before we go on to synovial joints, let’s stop and talk
about intervertebral discs.
INTERVERTEBRAL DISCS
Function is for shock absorption and a little movement.
Made up of outer ring of fibrocartilage called the
ANNULUS FIBROSIS, and the middle section is elastic
cartilage called the NUCLEUS PULPOSIS, which
provides the cushion.
Why do we need an annular fibrosis ring? The nucleus
pulposis is like a rubber ball. When you compress it,
it can be flattened. The ring keeps it from
compressing all the way.
Intervertebral Disc
Herniated Disc
•
•
•
•
HERNIATED intervertebral disc happens when stress is
put on it the wrong way. When you bend over, the disc
compresses anteriorly. If there’s a weakness there, the
annulus fibrosis tears, and the nucleus pulposis herniates
(pokes out).
It can press on the spinal nerves and cause a lot of pain
or some paralysis.
Improper lifting and pushing with the back can cause
this.
One treatment is to put a metal rod in to maintain the
distance between the discs.
Herniated Disc
Review:
Characterizing Joints by the
Types of Tissue Between Bones

Fibrous Joints
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Fibrous connective tissue (eg. suture, ligament, tooth)
Cartilaginous Joints
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Hyaline cartilage (eg. epiphyseal plate, costal cartilage)
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Fibrocartilage (eg. pubic symphysis)
Synovial Joints (Hyaline cartilage plus a capsule)
We have covered fibrous and cartilaginous joints.
Now we will discuss synovial joints.
Synovial Joints
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Synovial joints also have hyaline cartilage
connecting two bones, so they are sometimes
classified as a type of cartilaginous joint, but
because they are very different in structure and
function, they usually have their own
classification: Synovial Joints.
Cartilaginous joints (the hyaline type) are not
moveable.
Synovial joints also have hyaline cartilage, but
they have a capsule and are moveable.
Synovial Joints
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This is the most familiar type of joint and the
most common. It allows a wide range of motion
so it is functionally classified as a diarthrotic joint
(a diarthrosis)
Examples include the elbow, knee, knuckles, the
joints between the wrist and ankle bones
Synovial joints are the most structurally complex
type of joint, (having a joint cavity) and are the
most likely to develop uncomfortable and
crippling dysfunctions
Synovial Joints
Characteristics
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Enclosed chamber, flexible fibrous capsule
A cavity filled with fluid, synovial fluid
An inner membrane that produces
lubricating fluid, synovial membrane
Articular cartilages covering ends of bones
Reinforcing ligaments to stabilize
Innervated and vascular
Structures Associated With
Synovial Joints
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Articular Cartilage
Capsule
Synovial Fluid
Menisci (articular discs)
Ligaments
Bursae
Tendons
Synovial Joint Structure
In synovial joints,
the facing surfaces
of the two bones
are covered with
articular cartilage,
a layer of hyaline
cartilage about 2
mm thick
These surfaces are
separated by a narrow
space, the joint (articular)
cavity, containing a slippery
lubricant called synovial
fluid. This fluid is rich in
albumin and hyaluronic
acid, which give it a viscous,
slippery texture. It nourishes
the articular cartilages,
removes their wastes, and
makes movements at
synovial joints almost
friction-free
Capsule
A connective tissue
membrane (articular
capsule) encloses the
cavity and retains the
fluid.
It has an outer fibrous
capsule, which acts like
a sleeve; it is
continuous with the
periosteum of the
adjoining bones, and
an inner, cellular
synovial membrane,
which makes the
synovial fluid.
SYNOVIAL fLUID
• Lubricates the joint, allows smooth movement.
Its viscosity (thickness) changes with pressure,
so bones will never touch, even when you jump
up and down.
• Nourishes articular cartilage (which is
Avascular). Every movement puts pressure on
joint, forcing fluid into cartilage. Therefore, you
need pressure on joints to feed the cartilage.
Synovial Joint
Structure
In several synovial joints,
fibrocartilage grows inward
from the joint capsule and
forms a pad between the
articulating bones. When
the pad crosses the entire
joint capsule it is called an
articular disc, or a
MENISCUS. Some joints
(such as the knee) use
these MENISCI to act as a
guide for movement of the
bones to prevent unwanted
movement such as lateral
movement in the knee
(Common injury).
LIGAMENTS
•
•
The joint capsule alone is not strong enough, so
there are reinforcing LIGAMENTS, which provide
most of the strength of holding the bones to bones.
They are dense regular connective tissue.
In the knee joint, the collateral ligaments are the
main ligaments that keep the knee from moving
medially to laterally.
LIGAMENTS
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Ligaments take a long time to heal if torn because they do not
have blood vessels of their own, like bones do. They already
have enough fibroblasts and collagen, though, so they
eventually can heal. It is better to break a bone than tear a
ligament because bones have a better blood supply and heal
faster.
SPRAINS: are tears in a ligament, and are fairly serious. When
a tendon or ligament is sprained, it can take 6 months to heal,
and may even need surgery. Even a partial tear, you have to
be careful.
STRAIN: is a tear in a muscle, and is not as bad because it has
good circulation and heals faster. If you can walk on it and it
heals in a couple of days, it’s a strain.
BURSAE
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A BURSA is a sack of synovial fluid that is involved in lubrication by
serving as a cushion between a muscle/ligament or tendon/bone, etc.
It does not need to be attached to any bone; it is like a pillow
between the muscle and bone.
Bursae cushion muscles, help tendons slide more easily over the
joints, and sometimes enhance the mechanical effect of a muscle by
modifying the direction in which its tendon pulls.
It is lined by a synovial membrane which makes its synovial fluid. This
fluid can become excessive during overuse, and pinches nerves in
the area. What’s an inflamed bursa called? Bursitis.
Crackling sounds in joints are from the release of gas bubbles in the
synovial fluid.
It does not lead to arthritis.
Synovial Joint
The knee joint has
at least 13
bursae!
Bursitis is
inflammation of
a bursa, usually
due to
overexertion of
a joint.
Tendinitis is a
form of bursitis
in which a
tendon sheath is
inflamed
Bursae and Tendon Sheaths
Tendon sheaths are
also filled with synovial
fluid, and can become
inflamed with overuse.
Types of Synovial Joints
There are six types of synovial joints, characterized
by the motion allowed by the shapes of the bones.
1.
Plane
2.
Hinge
3.
Pivot
4.
Condyloid
5.
Saddle
6.
Ball and socket
Plane Joints
Allows motion in one
plane only (transverse or
frontal plane).
Examples are the carpal
and tarsal bones,
between the articular
processes of the
vertebrae, and at the
sternoclavicular joint
Hinge Joints
Allows motion in the
sagittal plane only.
Examples are the
elbow, knee, and IPJ
= interphalangeal
joints of the fingers
and toes
Pivot Joints
Allows for pivot
motion (transverse
plane).
Examples are the
atlantoaxial joint
between the first two
vertebrae (shake head
“no”) and proximal
radioulnar joint,
where the annular
ligament on the ulna
encircles the head of
the radius
Condyloid Joints
Their shape is like a
knob in a cup, so they
are called “condylar”.
Condylar joints allow
for motion in TWO
planes. Therefore, they
are “biaxial”.
Examples are the
Metacarpal-phalangeal
joints (MPJ’s)
Saddle Joints
Examples are at the base
of the thumb (between the
trapezium and metacarpal
I) and sternoclavicular
joint between the clavicle
and sternum.
Saddle joints are biaxial
joints (two planes of
movement); in primate
anatomy, allows for the
opposable thumb
Ball and Socket Joints
This type of joint
allows for all
three planes of
movement, so
they are
multiaxial.
Examples are the
shoulder and hip
joints.
Three Important Synovial Joints
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Knee Joint
Hip Joint
Shoulder Joint
The Knee Joint
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Tibiofemoral joint and patellofemoral joint
The largest and most complex diarthrosis
of the body
Hinge joint, but has movements of gliding, rolling and
rotation
3 articulations: lateral and medial articulations of
femur and tibia; intermediate articulation of patella
and femur. Note: Fibula does not articulate with the
femur, only with the tibia.
Extracapsular ligaments
Patellar ligament (patellar tendon)
 Passes from the apex and margins of the patella distally to the
tibial tuberosity
Medial collateral ligament
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Extends from the medial epicondyle of the femur to the medial
condyle of the tibia
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At its midpoint, its fibers are attached to the medial meniscus,
Lateral collateral ligament
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Extends inferiorly from lateral epicondyle of femur to lateral
surface of the fibular head
Two ligaments lie outside the
joint capsule:
• tibial (medial) collateral
ligament.
•fibular (lateral) collateral
ligament
The two collateral ligaments
prevent the knee from rotating
when the joint is extended.
Intracapsular ligaments of the
knee
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There are two ligaments that lie inside the joint capsule.
They are deep within the joint cavity, but they are not
inside the fluid-filled synovial cavity.
These ligaments cross each other in the form of an X:
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anterior cruciate ligament (ACL)
posterior cruciate ligament (PCL)
Intracapsular ligaments
Anterior cruciate ligament (ACL)
•
Weaker of the two cruciates
•
Slack when knee is flexed, taut when fully extended
•
Prevents posterior displacement of femur and hyperextension of knee joint
Posterior cruciate ligament (PCL)
•
Taut during flexion, prevents anterior displacement of femur on the tibia
•
Is the main stabilizing factor when weight-bearing during flexed knee
position (ie. Walking downhill.)
The ACL and PCL are named
according to whether they attach
to the anterior or posterior side of
the tibia, (not for their attachments
to the femur.)
When the knee is extended, the ACL
is pulled tight and prevents
hyperextension.
The PCL prevents the femur from
sliding off the front of the tibia and
prevents the tibia from being
displaced backward.
Menisci
Medial and Lateral Menisci
 Crescent (C-) shaped plates of fibrocartilage
located over the medial and lateral tibial
condyles
 Thicker laterally, thinner inside the joint
capsule
 Act like shock absorbers
 Thicker laterally, taper to thin unattached
edges at interior of the joint.
In the knee, two
fibrocartilages extend inward
from the left and right but do
not entirely cross the joint
Each is called a meniscus
Menisci absorb the shock of the
body weight jostling up and down
on the knee and prevent the femur
from rocking from side to side on
the tibia.
Anterior View of Flexed Knee
Figure 9.14e, f
Knee Joint
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
On the final lecture exam (in class at the
end of the semester), be able to label the
drawing with the names of all of the
structures of the knee joint, including the
bones, ligaments, cartilage, membranes,
capsule, menisci, etc.
Know the movements allowed and the
movements prevented by the anatomy of
the knee.
10 pt Essay Question: Label this
(1/2 point each)
Essay Answer (a)
Essay Answer (b)
Quadriceps tendon
Lateral Collateral
ligament
Lateral Meniscus
Medial Collateral
ligament
Medial Meniscus
Patellar ligament
(patellar tendon)
Medial Collateral
ligament
Lateral Collateral
ligament
Lateral Meniscus
Medial Meniscus
Posterior Cruciate
ligament
Hip Joint
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Strong, stable ball and socket joint,
most moveable of all joints
Transverse acetabular ligament (which
bridges the acetabular notch) holds
head in beyond its equator.
Hip Joint
The main factor responsible for stabilizing the hip joint is not
the ligament at the fovea capitis inside the articular capsule.
It is also not stabilized by the deep socket. The ligaments
around the head of the femur give it stability.
Hip Joint Ligaments
Iliofemoral ligament

Y shaped; Attaches to ant infer iliac spine and acetabular rim
proximally and inferior intertrochanteric line distally

Prevents hyperextension of the hip during standing
Pubofemoral ligament
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Runs from the superior ramus of the pubis and passes laterally and to
the intertrochanteric line (passing deep to the iliofemoral ligament.)

Prevents overabduction of the hip joint
Ischiofemoral ligament
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Runs from ischial part of acetabular rim, to the neck of femur (best
seen from posterior view.)

Prevents hyperextension of the hip by screwing the femoral head
deeper into the acetabulum
Ligament of the head of the femur (ligamentum teres)

Weak, little importance in strengthening hip joint

Runs from the transverse acetabular ligament and attaches to the pit
(fovea capitis) of head.
Hip Joint
Figure 9.13a, b
Posterior View of the Hip Joint
Figure 9.13c, d
Hip Ligaments

On the final lecture exam (in class at
the end of the semester), be able to
label the drawing with the names of the
ligaments that attach to the hip.
10 pt Essay Question: Label this
Essay Answer: 1 pt each
Anterior
Posterior
The Shoulder Joint
Diarthrotic, ball and socket joint:
Humeral head in glenoid cavity
Shoulder Joint (Glenohumeral Joint)
Ligaments:
Glenohumeral ligaments : 3 fibrous bands

From the anterior glenoid labrum to the anatomical neck of humerus

Reinforce the anterior part of the articular capsule (and are inside the
capsule, not visible from outside.)
Coracohumeral ligament

From base of coracoid process to anterior aspect of greater tubercle of
humerus
Transverse humeral ligament

Runs from greater to lesser tubercle of humerus

Creates a channel , bridging over the intertubercular groove

Site for tendon of long head of biceps brachii
Coracoacromial ligament

From inferior aspect of acromion to coracoid process

Forms a protective “arch” preventing superior displacement of the head

Supraspinatus muscle passes under this arch.
Shoulder Ligaments
Shoulder:Glenohumeral Joint
Shoulder Ligaments

On the final lecture exam (in class at
the end of the semester), be able to
label the drawing with the names of the
ligaments that attach the clavicle to the
scapula and to the head of the
humerus.
10 pt Essay Question: Label this
Essay Answer: ½ pt each
Ligaments of the Ankle Joint
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Anterior talofibular ligament
Posterior talofibular ligament
Calcaneofibular ligament
Deltoid ligament
Ligaments of the Ankle Joint
Figure 9.17c
Ligaments of the Ankle Joint
Figure 9.17d