2. Basic concepts in MSK - Joints Flashcards
What is a joint?
A joint is an articulation between two or more bones.
What is the relationship between the range of movement and stability in joints?
Higher the range of movement, the less stable and more likely to be dislocated
What are the three types of joints?
fibrous, cartilaginous, synovial
What are fibrous joints? How stable/mobile are they?
Fibrous joints are united by collagen fibres. They have very limited mobility (i.e. poor range of movement) and high stability.
Gives some examples of fibrous joints
- Sutures of the skull
- Inferior tibiofibular joint (at the ankle)
- Radioulnar interosseous membrane (in the forearm)
- Posterior sacroiliac joint (in the pelvis)
- Joint between roots of a tooth and the bone of the mandible or maxilla.
What are cartilaginous joints? Where are they found? How are they categorised?
Joints that use cartilage to unite bones are called cartilaginous joints. They are typically found in the midline of the body and also in the epiphyseal plates of long bones.
Primary and secondary
Describe primary cartilaginous joints. Give examples
- united by hyaline cartilage
- completely immobile
E.g. first sternocostal joint, xiphisternal joint, epiphyseal growth plates
Describe secondary cartilaginous joints. Give examples
- aka symphyses
- articulating bones are covered with hyaline cartilage with a pad of fibrocartilage between them
- usually found in midline of the body
E.g. symphysis pubis in pelvis, intervertebral discs, manubriosternal joint
Which joints are most mobile?
Synovial joints - less stable
What is a synovial joint? Mobility?
Synovial joints have a Joint cavity containing synovial fluid (egg white). Lubricates articular surfaces therefore joints have high degree of mobility and widespread throughout skeleton.
What covers the articulating surfaces of synovial joints? What are the exceptions?
Covered by hyaline cartilage except :
acromioclavicular joint
sternoclavicular joint
temporomandibular joint
covered with fibrocartilage
What is the advantage of covering joints with hyaline cartilage?
Hyaline cartilage usually permits smooth, low-friction movement and resists
compressive forces within the joint by acting as a shock absorber.
Describe the structure of the FIBROUS CAPSULE of synovial joints
- Composed of collagen in longitudinal and interlacing bundles.
- Encloses joint except where it is interrupted by synovial protrusions which form bursae.
- continuous with the periosteum covering the surface of the adjacent bones.
Function of fibrous capsule?
The capsule stabilises the joint; it permits movement but resists dislocation
Describe the structure of SYNOVIAL MEMBRANE
- Thin highly-vascularised membrane
- Produces synovial fluid
- Lines the joint capsule and covers any exposed osseous surfaces. It also lines tendon sheaths and bursae.
- Does not cover articular cartilage or intra-articular discs / menisci.
What does the shape of synovial joint dictate?
The shape of a synovial joint dictates the type of movement that the joint can perform
What are the types of synovial joints?
There are plane joints, hinge joints, saddle joints, condyloid (or
ellipsoid) joints, pivot joints and ball and socket joints
What are plane joints?
- where two flat surfaces slide against each other
- allow for smooth movement in several directions along a single plane
E.g. carpal bones of wrist, tarsal bones of foot, facet joints between vertebral articular processes of the spine
What are condyloid joints?
- two elliptical bowls nested
- One of the key features that differentiates condyloid joints from ball-andsocket joints is that their elliptical shape prevents rotation from occurring
E.g. Atlanto-occiptal joint at the base of the skull and the radiocaral joint of the wrist
What are saddle joints?
- two bones that fit together
- allows motion in two different planes at the same time with a degree of sliding
E.g. the first carpometacarpal joint at the base of the thumb
What are hinge joints?
- allow for stable flexion and extension without sliding or deviation
- Movement only takes place in a single anatomical plane
E.g. elbow joint
What are pivot joints?
- comprise a peg within a ring-shaped hole
- allow rotational motion without gliding/ bending/ sideways displacement
E.g. Atlanto-axial joint between the first and second cervical vertebrae allows the head to rotate whilst maintaining the stability of the head on the neck
What are ball and socket joints?
- allow movement in several directions without slippage
- most mobile synovial joint
- permit flexion-extension, abduction-adduction, lateral rotation-medial rotation, circumduction
E.g. hips and shoulders
What are synovial joints surrounded by that maintains the blood supply regardless of the position of the joint?
Synovial joints are surrounded by a plexus of arteries
Which articular surfaces are not lined by synovial membrane?
The knee joint contains intra-articular fibrocartilaginous menisci and thejoints between the vertebrae contain intervertebral discs. These intraarticular structures do not have a synovial covering.
what factors will influence the range of motion of individual joints? Think about both health and disease.
- Structure or shape of the articulating bones
- Strength and tension of the joint ligaments
- Arrangement and tone of muscles around the joint
- Apposition of neighbouring soft tissues (i.e. are they restrictingmovement?)
- Effect of hormones (e.g. relaxin relaxes pelvic joints toward the end of pregnancy)
- Disuse of a joint
Articular cartilage is avascular, and the fibrous capsule and ligaments have a poor blood supply so how do the articulating cartilaginous surfaces received blood?
Synovial membrane has rich blood supply so maintains nutrient flow via synovial fluid to articulating cartilaginous surfaces.
How do synovial joints develop?
• The synovial joints will form between the adjacent cartilage models, in an area called the joint interzone.
• Cells at the centre of this interzone region undergo apoptosis (programmed cell death) to form the joint cavity,
• while surrounding mesenchyme cells from the perichondrium will form the periosteum where they lie in contact with bone, and the joint capsule
• supporting ligament lie in contact with the
developing joint
What happens when there is incomplete apoptosis of cartilage in synovial joint development?
What happens when there is incomplete apoptosis of cartilage in synovial joint development?
example of first class levers?
Neck joint
Example of second class levers?
Ankle joint
example of third class lever
elbow joint
What are first class levers?
Fulcrum is in the centre
Load is at one end
Effort is applied on the opposite side of the fulcrum to the load
e.g scissors
What are second class levers?
When the load is located between the fulcrum and the effort that is applied to lift the load e.g wheelbarrow
What are third class levers?
The effort is applied between the fulcrum and the load
e.g forceps
Define olecranon
Pointy bit of elbow
