Joints

By: Terri
Date: October 5, 2010
Time to read: 10 min.

Before you start learning about the joints itself, it is important to learn about the joints articulation/movements so that you will understand better how the different types of joints result in those movements.

Extension & Flexion
Abduction & Adduction
Circumduction
- all of the above
Medial & Lateral rotation
Lateral flexion
Pronation & Supination
Eversion & Inversion
Protraction & Retraction
Elevation & Depression
Opposition
Dorsiflexion & Plantarflexion

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Joints

Definition: Is the site where 2 bones meet.

Classification of joints

Functional classification (based on degree of movement)
- Synarthroses
  - no movements at all
- Amphiarthroses
  - Slight movements
- Diarthroses
  - Freely movable
Structural classification
- Fibrous joints
  - bones joined by fibrous tissue
  - Categories
    - Sutures
      - skull bones
    - Syndesmoses
      - inferior tibio-fibular joint
    - Gomphoses
      - tooth sockets
- Cartilaginous joints
  - bones joined by cartilage
  - Categories
    - Synchondroses (Primary)
      - No movements
      - Epiphyseal plate (hyalin cartilage)
    - Symphyses (Secondary)
      - Slight movements
      - Intervertebral discs
- Synovial joint
  - bones separated by fluid containing cavity
  - Examples:
    - Knee
    - Elbow
  - Contains
    - Articular cartilage
      - hyaline cartilage
      - covers the bone surfaces
    - Joint cavity
    - Articular capsule
      - Fibrous capsule
      - Synovial membrane
    - Synovial fluid
    - Reinforcing ligaments
  - Types of synovial joint
    - Plane joint
      - intercarpal joint
      - gliding movement
      - nonaxial
    - Hinge joint
      - elbow joint
      - extend and flex only
      - uniaxial
    - Pivot joint
      - proximal radio-ulnar joint
      - rotation
      - uniaxial
    - Condyloid joint
      - metacarpo-phalangeal joint
      - biaxial
    - Saddle joint
      - carpo-metacarpal joint
      - only in thumb
      - biaxial
    - Ball & Socket joint
      - shoulder joint
      - all movements
      - multiaxial

Axis of joint movements

Non-axial
- only slipping possible
Uniaxial
- movements in 1 plane
Biaxial
- movements in 2 planes
Multiaxial
- movements around all 3 plants

Reinforcing ligaments

Capsular
- thickening of the capsule
- hip joint
Extracapsular
- shoulder joint
Intracapsular
- knee joint

Bursae & Tendon sheaths

Bursae
- flattened fibrous sac lined with synovial membrane and filled with synovial fluid
Tendon sheath
- elongated bursae into which a tendon sheath is invaginated

Purpose: Reduce friction between the bones.

Stability of joints

If stability is not maintained, joint can get dislocated.

Articular surfaces
- if articular surfaces are fitting together, stability is increased
Ligaments
- surr
  ounding the joints provides stability
- the greater the number of ligaments, the stronger they are
  - more stable
Surrounding muscles and their tone
- tendon and muscles crossing the joints stabilize the joint

Blood supply of joints

From the arteries surrounding the joint
- articular arteries
  - forms anastomosing network

Nerve supply of joints

From the nerves supplying the muscles which crosses the joints
- Hilton’s law

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Shoulder Joint (Glenohumeral joint)

Characteristics

Synovial joint
- Ball & Socket joint
- Multiaxial
  - Ball: Humerus
  - Socket: Glenoid cavity
    - pear shaped
    - shallow
      - deepened by a rim of fibrocartilage attached to the rim of glenoid cavity
        glenoidal lambrum
    - not reciprocal
    - only in contact with 1/3 of humeral head

Stability of joint

Muscle: Rotator cuff (of Codmann)
- important due to ligament laxity
- All sides except inferior part (SITS)
  - From Infront
    - Subscapularis
  - From behind
    - Infraspinatus
    - Teres Minor
  - From above
    - Supraspinatus
Ligaments
- Capsular ligament (Glenohumeral ligament)
  - Superior
  - Middle
  - Inferior
    - Generally lax/loose
    - Tightens only at extreme of movements

Reasons for shoulder instability:

*No reciprocal curvature of articular surfaces
Ligaments weak and lax
Gravity

Factors maintaining shoulder stability:

Muscles and Tendons
- Yes
Surface tension & vacuum
- Synovial fluid
- Adhesive & Cohesive Force
~~Bones~~
- Almost nil
~~Ligaments~~
- Negligible

Shoulder joint movements & muscle involvement

Transverse axis
- Flexion
  - Deltoid (anterior fibres)
  - Pectoralis major (clavicular head)
- Extension
  - Deltoid (posterior fibres)
  - Latissimus dorsi
Anteroposterior axis
- Adduction
  - Pectoralis major
  - Latissimus dorsi
  - Teres major
  - Triceps brachii (long head)
- Abduction
  - Deltoid
  - Supraspinatus
  - Serratus anterior
  - Trapezius (upper and lower fibres)
Vertical axis
- Medial rotation
  - Pectoralis major
  - Deltoid (anterior fibres)
  - Latissimus dorsi
  - Teres major
- Lateral rotation
  - Deltoid (posterior fibres)
  - Infraspinatus
  - Teres minor
Circumduction
- occurs at 180 degrees
  - movement partly at shoulder joint, partly at pectoral girdle
  - First 15 – 30 degrees
    - Supraspinatus
  - Up til 90 degrees
    - Deltoid
  - 90 – 180 degrees
    - Roration of scapula
      - Trapezius
      - Serratus anterior

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Hip Joints (Acetabulofemoral joint)

Characteristics

Synovial joint
Multiaxial
Ball & Socket joint
- Ball: Femoral head
  - covered by hyalin cartilage except for fovea
- Socket: Acetabulum
  - cup shaped
  - large & deep
  - narrow mouth
    - mouth made narrower by a rim of fibrocartilage which is attached to the rim of acetabular cavity
      - acetabular labrum
  - articular surface
    - horse-shoe shaped
  - Reciprocally curved

Hip joint stability

Muscles
- Lateral
  - Tensor fasciae latae muscle
  - Iliotibial tract
  - Vastus lateralis muscle
- Posterior
  - Gluteus maximus
  - Hamstring muscle
    - Semitendinous muscle
    - Semimembranous muscle
    - Biceps femoris muscle
  - Adductor magnus muscle
  - Gracilis muscle
- Deep
  - Gluteus medius
  - Obturator gamellus muscle
  - Obturator internus muscle
  - Inferior gamellus muscle
  - Quadratus femoris muscle
  - Biceps femoris muscle (long head)
  - Semitendinous muscle
  - Semimembranous muscle
Ligaments
- Iliofemoral
- Ischiofemoral
- Pubofemoral
- Ligamentum teres
  - ligament of head of femur
- Transverse acetabular

Hip joint movements

Same as movements of shoulder joints

Factors for hip joint stability

Shape
- Reciprocal curvatures
  - The articular surfaces are configured and positioned in such a way that normal loading enhances the closeness of their fit
  - better than shoulder joint
Ligaments
- major stability influence
  - guide and align normal joints through their range of motion
- strong & inelastic structure
  - limit articular motion
  - iliofemoral joint one of the strongest in the body
- thick capsule
Muscles
- yes, but not primary form of support
- primary role
  - steady the pelvis on the lower limbs
  - maintain posture
Surface tension
Body weight

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Knee joint

Characteristics

Largest joint in the body!
Synovial joint
- Modified hinge joint
Composed of 3 joints
- Condylar
  - Medial femorotibial
  - Lateral femorotibial
- Saddle
  - Femoropatellar
Articular surfaces
- Condyles of femur
- Condyles of tibia
- Patella
Mobility
- by bones
Stability
- by soft tissues

Stability of joint

Ligaments
- Fibrous capsule
  - Only in posterior
    - deficient in front
  - Pierced by
    - suprapatellar bursae
    - tendon of popliteus
- Patellar Ligament / Ligamentum patellae
  - Tendon of quadratum femoris
- Tibia collateral ligament
  - From medial epicondyle of femur
  - To tibia
- Fibular collateral ligament
  - From lateral epicondyle of femur
  - To head of fibula
- Anterior cruciate ligament
  - Named by attachment to tibia
  - Taut in extension
- Posterior cruciate ligament
  - Named by attachment to tibia
  - Taut in flexion
- Coronary ligament
- Oblique popliteal ligament
- Arcuate popliteal ligament
Muscles
- Extensors
  - Quadriceps femoris
  - Tensor fasciae latae
- Flexors
  - Hamstrings
    - Biceps
    - Semitendinosus
    - Semimembranosus
- Medial Rotators
  - Popliteus
  - Semitendinosus
  - Semimembranosus
- Lateral Rotators
  - Biceps femoris

Movements of muscles

Extension, Flexion
Medial & Lateral rotators
Screw home movement
- locking/unlocking
- This is the name given to the action when a knee reaches full extension and just as the knee locks into hyperextension the knee rotates in an outward direction just a few degrees. This has the effect of putting most of the weight onto the cartilage, menisci, and bones of the joint while giving a rest to the muscles of the thigh and ca
  lf. What allows for this is that the medial femoral condyle is slightly curved and the medial condylar notch is slightly longer than the lateral condylar notch
Accessory movements
- only on partially flexed knee
- Wider range of rotation
- AP gliding of tibia on femur
- Some amount of abduction & adduction
- Some amount of separation of tibia from femur

Factors maintaining stability of knee joint

Anteroposterior stability
- Cruciate ligaments
Side-to-side stability
- Collateral ligaments
Capsular ligaments
- weak
- reinforced by tendinous expansions
During partial flexion
- Iliotibial tract

Reasons for instability of knee joint

Due to incongruence
- Tibial condyles too small & shallow for the large & convex femoral condyles
- Angulation of thigh on leg
  - shallow surfaces of patellar & femur

Menisci

Menisci are semilunar fibrocartilages
- that try to deepen the articular surfaces of the tibial condyles
2 attached ends
2 borders
- 1 fixed
- 1 free
2 surfaces
- 1 concave
- 1 flat
2 parts
- outer vascular
- inner avascular
Medial meniscus
- Semicircular
- attached to the tibial collateral ligament
Lateral meniscus
- Circular
- attached to medial condyle of femur by
  - 2 meniscofemoral ligaments
- attached to popliteal tendon (tendon of popliteus)

Clinical anatomy (look up later)

Q angle
- Genu valgum
  - angle less than 165 degrees
- Genu varum
  - angle more than 180 degrees
Knee jerk
Osteoarthritis
Meniscal tears
Cruciate ligament injury
Bursitis
Patellar fracture
Xray

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Ankle joint (Talocrural joint)

Characteristics

Synovial joint
- Hinge joint
Made up of 3 bones
- Tibia
- Fibular
- Talus
  - distributes the weight

Stability

Strong structure
Strong ligaments
- Medial collateral ligament (Deltoid ligament)
  - tibionavicular ligament
  - calcaneotibial ligament
  - anterior talotibial ligament
  - posterior talotibial ligament
- Lateral collateral ligament
  - anterior talofibular ligament
  - calcaneofibular ligament
  - talocalcaneal ligament
  - posterior talocalcaneal ligament
  - posterior talofibular ligament
Tendinous reinforcement

Movements (2 only)

Dorsiflexion
Plantarflexion

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Joints of the foot

Tibiofibular joints
- Superior
- Middle
- Inferior
Intertarsal
- Subtalar joint (Talocalcanean)
- Talocalcaneonavicular joint
- Calcaneocuboid joint
- Transverse tarsal joint
- Smaller joints
  - Cuneonavicular
  - Cuboideonavicular
  - Intercuneiform
  - Cuneocuboid
Tarsometatarsal
Intermetatarsal
Metatarsophalangeal
Interphalangeal

Movements of the foot

Inversion (plantarflexion + adduction of foot)
Eversion (plantarflexion + abduction of foot)
- Subtalar joint
- Talocalcaneonavicular joint
  - calcaneum and navicular move medially/laterally around the talus
    - carrying the foot with them
Metatarsophalangeal joints (ellipsoidal joints) – movements
- Extension
- Flexion
- Abduction
- Adduction
Interphalangeal joints (hinge joints)
- Extension
- Flexion

Arches of the foot

Longitudinal arch
- Medial longitudinal arch
  - Posterior pillar
    - Calcaneum
  - Anterior pillar
    - Navicular
    - Cuneiforms
    - Medial 3 metatarsals
  - Summit
    - Talus
- Lateral longitudinal arch
  - Posterior pillar
    - Calcaneum
  - Anterior pillar
    - Cuboid
    - Lateral 2 metatarsals
  - Summit
    - Calcaneo-cuboid articulation
Transverse arch

Clinical anatomy of the arches

Footprint
Pes planus
- flat foot
Pes cavus
- high arch of the foot that does not flatten with weight bearing
Talipes equinovarus
- club foot

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Elbow joint

Characteristics

Synovial joint
- Hinge joint
Composed of 2 joints
- radio-capitulum joint
  - articular surfaces:
    - head of radius
    - capitulum (of humerus)
- humero-ulnar joint
  - articular surfaces:
    - Trochlea notch of ulna
    - Trochlea of humerus
Elbow joint continuous with radio-ulnar joint
Bony landmarks
- Humerus
  - Radial fossa
  - Coronoid fossa
  - Olecranon fossa

Stability

Ligaments
- Capsule
  - Superiorly
    - encloses capitulum, trochlea, radial fossa, coronoid fossa & olecranon fossa
  - Inferiorly
    - attached to the trochlea notch & annular ligament
- Radial collateral ligament
  - fan shaped
  - attached to
    - lateral epicondyle
    - annular ligament
- Ulnar collateral ligament
  - Triangular
    - anterior, posterior & oblique bands
  - attached to
    - medial epicondyle
    - ulna

Blood & Nerve supply of the elbow joints

Blood supply
- anastomosis around the joint
- Main artery
  - brachial artery
  - branches into collateral arteries
Nerve supply
- Ulnar nerve
- Median nerve
- Radial nerve
- Musculocutaneous nerve

Movements of elbow joints

Flexion
- Brachialis
- Biceps
- Brachioradialis
Extension
- Triceps
- Anconeus

Relations

Biceps tendon
Brachial artery
Median nerve

Elbow joint – Carrying angle

Transverse axis of joint directed medially and laterally
- Due to this,extended forearm not in line with arm
- makes an angle of about 163 degrees
Disappears in
- full flexion
- pronation
Anomaly
- cubital valgus
  - cubitus angle >15º, resulting the forearm deviating outwards
- cubital varus
  - resulting the forearm deviating towards the midline

Clinical anatomy

Distension
- occurs posteriorly due to effusion
- aspirated posteriorly
Dislocation
- usually posteriorly
- associated with fracture of coronoid
- triangular relationship is lost between
  - Olecranon
  - 2 epicondyles
Subluxation of head of radius
- occurs in children
- when arm is pulled in pronation
- radial head slips out from annular ligament
Tennis elbow
- abrupt pronation
  - results in tear of radial collateral ligament
  - or extensor ligaments originating from lateral epicondyle

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Radio-ulnar joint

Characteristics

3 joints together

Superior
- Synovial joint
  - pivot type
- Articular surfaces
  - circumferance of the head of radius
  - osseofibrous ring
    - formed by radial notch of ulnar & annular ligament
- Blood supply
  - anastomosis around the lateral side of elbow joint
- Nerve supply
  - Median nerve
  - Radial nerve
  - Musculocutaneous nerve
- Movements
  - Suppination
    - Palms facing upwards
    - Antigravity (more powerful)
    - Muscles
      - Biceps muscle
      - Suppinator muscle
  - Pronation
    - Palms facing downwards
    - Gravity assisted
    - Muscles
      - Pronator quadratus (Main)
      - Pronator teres
- Ligaments
  - Annular ligament
    - Forms 4/5 of articular surface
    - attached to margins of radial notch of ulna
  - Quadrate ligament
    - Attached to
      - neck of the radius
      - lower margin of the radial notch of the ulna
Middle
- Interosseous membrane
Inferior
- Interosseous membrane
  - connects the shafts of the radius and ulna
  - fibres run radially and medially
  - from radius to ulnar
- Anterior surface
  - related to
    - flexor muscles
    - pronator quadratus
    - anterior interosseous nerves and vessels
- Posterior surface
  - related to
    - extensor muscles
    - suppinator
    - posterior interosseous nerve
- Functions
  - binds the bones together
  - provides attachment to muscles
  - transmit forces from hand to ulna
  - no movements

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Wrist joints (Radiocarpal joint)

Characteristics

Synovial joint
- ellipsoidal
Articular surfaces
- lower end of radius
- articular disc of inferior radiocarpal joint
Related to carpal bones
- scaphoid
- lunate
- triquetral
Blood supply
- Anterior carpal arch
- Posterior carpal arch
Nerve supply
- Anterior interosseous nerve
- Posterior interosseous nerve
Movements
- Flexion
  - occurs more in the midcarpal joint
  - Muscles involved
    - Primary
      - Flexor carpi radialis (FCR)
      - Flexor carpi ulnaris (FCU)
      - Policis longus (PL)
    - Secondary
      - long flexors of the fingers & thumb
- Extension
  - occurs mainly in the wrist
  - Muscles involved
    - Primary
      - Extensor carpi radialis longus (ECRL)
      - Extensor carpi radialis brevis (ECRB)
      - Extensor carpi ulnaris (ECU)
    - Secondary
      - Long extensors of fingers & thumb
- Abduction
  - occurs more in the midcarpal joint
  - Muscles involved
    - Flexor carpi radialis (FCR)
    - Extensor carpi radialis longus (ECRL)
    - Extensor carpi radialis brevis (ECRB)
    - Abductor pollicis longus (APL)
    - Extensor pollicis brevis (EPB)
- Adduction
  - occurs mainly in the wrist
  - Muscles involved
    - Flexor carpi ulnaris (FCU)
    - Extensor carpi ulnaris (ECU)
- Circumduction
  - from all of the above
Ligaments
- Capsule
- Palmar radiocarpal ligament
- Palmar ulnarcarpal ligament
- Dorsal radiocarpal ligament
- Radial collateral ligament
- Ulnar collateral ligament

Clinical anatomy

Commonly involved in rheumatoid arthritis
- Affects the metacarpo-phalangeal & proximal interphalangeal joints
Common site for a ganglion
- A cystic swelling due to the mucoid degeneration of synovial sheaths around the tendons

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Joints of the hand

Intercarpal joints
- 2 joints
  - Pisotriquetral joint
    - Pisiform & Triquetral carpal bones
  - Midcarpal joint
    - between proximal and distal rows
- Ligament
  - Interosseous ligament
Carpometacarpal joints
- Thumb
  - Independent joint
  - 1st carpometacarpal joint has separate joint cavity
  - allows free movements for thumb
- Movements
  - Extension
  - Flexion
  - Abduction
  - Adduction
  - Circumduction
  - Opposition
Intermetacarpal joint
Metacarpophalangeal joint
- Synovial joints
  - condylar joint
- Movements
  - Extension
    - Limited extension
  - Flexion
    - Free flexion
    - Side to side movement in flexion
  - Abduction
  - Adduction
  - Circumduction
    - 1st MCP no circumduction
  - Opposition
Interphalangeal joint
- Synovial joint
  - Hinge joint
- Movements (2 only!)
  - Extension
  - Flexion