Source: APK2100C Study Guide SLOs, University of Florida
Difficulty: Intermediate | Prerequisites: Chapter 6 (bone tissue, cartilage types, periosteum/endosteum)
Tags: joints, articulations, synovial joints, fibrous joints, cartilaginous joints, synarthrosis, amphiarthrosis, diarthrosis, sutures, syndesmosis, gomphosis, synchondrosis, symphysis, synovial capsule, synovial fluid, articular cartilage, bursae, tendon sheaths, ligaments, joint movements, flexion, extension, abduction, adduction, rotation, circumduction, knee joint, shoulder joint, hip joint
Joints are where the action happens. You already know the bones (Ch. 6) – now you need to understand how they connect to one another and what kinds of movement those connections permit. This chapter classifies joints two ways (by structure and by function), then drills into the details of synovial joints, which are the most clinically relevant because they allow the most movement and are the most prone to injury. If you are shaky on cartilage types (hyaline, elastic, fibrocartilage), go back to Chapter 6, because the structural classification of joints depends heavily on which connective tissue holds the bones together.
Joints are classified structurally (fibrous, cartilaginous, synovial) and functionally (immovable, slightly movable, freely movable). Synovial joints are the most common and most mobile, sharing features like a joint capsule, synovial fluid, and articular cartilage. The six types of synovial joints each permit specific movements in specific anatomical planes.
Joint (articulation)
The site where two or more rigid elements of the skeleton meet. Joints allow movement and provide structural support.
Synarthrosis
A functionally immovable joint. Think of skull sutures: the bones are locked together.
Amphiarthrosis
A slightly movable joint. In simple terms, there is a small amount of give, like the intervertebral discs between your vertebrae.
Diarthrosis
A freely movable joint. All synovial joints fall into this category.
Fibrous joint
A joint where bones are connected by dense collagen fibres with no synovial cavity. Movement ranges from none to slight.
Suture
A fibrous joint found only in the skull, held together by very short, interconnecting fibres. Functionally a synarthrosis.
Syndesmosis
A fibrous joint where bones are connected by a ligament that can vary in length. Longer fibres allow more movement (amphiarthrosis or synarthrosis). Examples: middle radioulnar joint, distal tibiofibular joint.
Gomphosis
A peg-in-socket fibrous joint where the periodontal ligament holds a tooth in its socket. Functionally a synarthrosis. Found only between teeth and their bony sockets.
Cartilaginous joint
A joint where bones are connected by cartilage (hyaline or fibrocartilage) with no synovial cavity.
Synchondrosis
A cartilaginous joint where bones are held together by hyaline cartilage. Functionally a synarthrosis (though slight movement may occur during growth). Examples: epiphyseal plate, first sternocostal joint.
Symphysis
A cartilaginous joint where bones are held together by a fibrocartilage pad or disc, allowing slight flexibility and shock absorption. Functionally an amphiarthrosis. Examples: intervertebral discs, pubic symphysis.
Synovial joint
A joint with a synovial cavity, reinforcing ligaments, and articular cartilage. All synovial joints are diarthrotic (freely movable).
Synovial capsule
A sleeve-like capsule enclosing the synovial cavity, consisting of an outer fibrous layer (dense irregular CT) and an inner synovial membrane (loose CT that secretes synovial fluid).
Synovial fluid (synovium)
A viscous fluid with a consistency similar to raw egg whites, secreted by the inner synovial membrane. It lubricates the joint, reduces friction, and nourishes the articular cartilage.
Articular cartilage
Smooth, elastic hyaline cartilage covering the ends of bones at a synovial joint. It absorbs shock, distributes loads, and reduces friction.
Bursa (plural: bursae)
A small, sac-like structure containing synovial fluid, found in areas where friction is likely. Reduces friction between body parts that rub against one another.
Tendon sheath
An elongated, tube-like bursa wrapping around a tendon, especially where it crosses a joint. It has a fibrous outer layer and an inner layer producing synovial fluid.
Capsular ligament
A thickened band within the joint capsule itself that stabilises the joint and limits excessive movement. Example: glenohumeral ligament.
Extracapsular ligament
A ligament located outside the joint capsule, helping maintain joint position during dynamic activities. Example: medial and lateral collateral ligaments (MCL and LCL).
Intracapsular ligament
A ligament located inside the joint capsule but outside the synovial cavity, stabilising the joint and guiding movement. Example: anterior and posterior cruciate ligaments (ACL and PCL).
Functional redundancy (of joint innervation/blood supply)
The overlapping presence of multiple nerve and blood vessel pathways serving a joint. This means if one nerve or vessel is damaged, the joint can still function, heal, and provide sensory feedback.
Flexion
Movement that decreases the angle between two body parts. Occurs in the sagittal plane.
Extension
Movement that increases the angle between two body parts, returning toward anatomical position. Occurs in the sagittal plane.
Hyperextension
Extension beyond the normal range of motion, producing an angle greater than 180 degrees. Occurs in the sagittal plane.
Abduction
Movement of a limb away from the midline of the body. Occurs in the frontal (coronal) plane.
Adduction
Movement of a limb toward the midline of the body. Occurs in the frontal (coronal) plane.
Circumduction
A circular movement combining flexion, extension, abduction, and adduction. Occurs at ball-and-socket joints.
Rotation
Movement of a body part around its own axis, in either a medial (internal) or lateral (external) direction.
Pronation
Rotation of the forearm so the palm faces downward (radius crosses over the ulna).
Supination
Rotation of the forearm so the palm faces upward (radius and ulna are parallel).
Joints can be classified two ways:
Structural classification – based on anatomical features, specifically the presence or absence of a synovial cavity and the type of connective tissue binding the bones
Fibrous joints (dense collagen fibres)
Cartilaginous joints (cartilage)
Synovial joints (ligaments, synovial cavity)
Functional classification – based on the type and degree of movement permitted
Synarthroses (immovable)
Amphiarthroses (slightly movable)
Diarthroses (freely movable)
Bones connected by dense collagen fibres, no synovial cavity. Three subtypes:
Sutures – very short interconnecting fibres, dense fibrous CT, synarthrosis, found only in the skull
Syndesmoses – bones connected by a ligament, fibre length varies (longer fibres = more movement), amphiarthrosis or synarthrosis. Examples: middle radioulnar joint, distal tibiofibular joint
Gomphoses – peg-in-socket joint, periodontal ligament holds tooth in socket, synarthrosis, found only between teeth and their sockets
Bones connected by cartilage, no synovial cavity. Two subtypes:
Synchondroses – hyaline cartilage bridges the bones, little to no movement (synarthrosis, though slight movement may occur during growth). Examples: epiphyseal plate, first sternocostal joint
Symphyses – fibrocartilage pad or disc allows slight flexibility and shock absorption (amphiarthrosis). Examples: intervertebral discs, pubic symphysis
All synovial joints share these structural features:
Reinforcing ligaments holding bones together
A synovial cavity
Articular cartilage covering bone surfaces
Rich innervation and blood supply
All synovial joints are functionally diarthrotic (freely movable). The shape of articular surfaces, ligaments, and surrounding muscles determines the balance between stability and mobility at each joint.
Synovial capsule – outer fibrous layer (dense irregular CT, continuous with periosteum) provides support and stability; inner synovial membrane (loose CT) secretes synovial fluid and covers non-cartilage bony surfaces inside the capsule
Synovial fluid – viscous, egg-white-consistency fluid that lubricates, reduces friction, and nourishes articular cartilage
Articular cartilage – hyaline cartilage on bone ends, smooth and elastic, absorbs shock and distributes loads
Bursae – small sacs of synovial fluid in high-friction areas, reducing friction and allowing smooth movement
Tendon sheaths – elongated tube-like bursae wrapping tendons (especially those crossing joints), lubricating to prevent irritation
Capsular – thickened band within the joint capsule itself. Stabilises joint structure and limits excessive movement. Example: glenohumeral ligament.
Extracapsular – located outside the joint capsule. Maintains the joint's position during dynamic activity. Example: MCL and LCL of the knee.
Intracapsular – located inside the joint capsule but outside the synovial cavity. Stabilises the joint and guides movement. Example: ACL and PCL.
Planar (gliding) – flat articular surfaces, nonaxial gliding movement in the transverse plane. Examples: intercarpal joint, intertarsal joint, joints between vertebral articular surfaces.
Hinge – cylinder-and-trough surfaces, flexion/extension in the sagittal plane. Examples: elbow, interphalangeal joints.
Pivot – sleeve-and-axle surfaces, rotation (pronation/supination) in the transverse plane. Example: proximal radioulnar joint.
Condylar (ellipsoid) – oval articular surfaces, flexion/extension and abduction/adduction in the sagittal and frontal planes. Examples: metacarpophalangeal joint, wrist joint.
Saddle – concave-and-convex surfaces, flexion/extension and abduction/adduction in the sagittal and frontal planes. Example: carpometacarpal joint of the thumb.
Ball-and-socket – cup and spherical head, flexion/extension, abduction/adduction, and rotation in all three planes. Examples: shoulder (glenohumeral) and hip (femorocoxal) joints.
Flexion/extension/hyperextension – all occur in the sagittal plane
Occur at ball-and-socket, hinge, condyloid, and saddle joints
Abduction/adduction – occur in the frontal plane
Occur at ball-and-socket, condyloid, and saddle joints
Circumduction – circular movement combining all of the above, occurs at ball-and-socket joints
Rotation – movement around a body part's own axis, medial (internal) or lateral (external)
Opposition – thumb moves across the palm to touch the fingertips. Made possible by the saddle joint at the carpometacarpal joint of the thumb.
Elevation/depression – lifting a body part superiorly (e.g. closing the mouth) or moving it inferiorly (e.g. opening the mouth). Also seen at the scapula and shoulder.
Protraction/retraction – moving the mandible anteriorly or posteriorly (jutting jaw forward vs. pulling it back).
Inversion/eversion – turning the sole of the foot medially (inversion) or laterally (eversion).
Dorsiflexion/plantarflexion – lifting the foot so its top approaches the shin (dorsiflexion) or depressing the foot and elevating the heel (plantarflexion, also called eversion in the source, but more precisely this is pointing the toes downward).
Sternoclavicular joint
Bony landmarks: manubrium of sternum, medial end of clavicle
Cartilaginous structure: fibrocartilaginous articular disc
Reinforcing ligaments: anterior and posterior sternoclavicular ligaments, costoclavicular ligament, interclavicular ligament
Classification: synovial joint (saddle)
Glenohumeral joint (shoulder)
Bony landmarks: glenoid fossa of scapula, head of humerus, coracoid process
Cartilaginous structure: glenoid labrum
Reinforcing ligaments: glenohumeral ligament, coracohumeral ligament, transverse humeral ligament
Classification: synovial joint (ball-and-socket)
Femorocoxal joint (hip)
Bony landmarks: head of femur, acetabular fossa
Cartilaginous structure: acetabular labrum
Reinforcing ligaments: iliofemoral (one of the strongest in the body), pubofemoral, ischiofemoral, ligamentum teres
Classification: synovial joint (ball-and-socket)
Femorotibular joint (knee)
Largest, most complex joint in the body
Modified hinge joint: main action is flexion/extension, with some medial/lateral rotation
Bony landmarks: medial and lateral condyles of femur, tibial plateau. Note: the fibula is not directly involved in the knee joint.
Cartilaginous structures: medial and lateral menisci
Reinforcing ligaments: ACL (intracapsular), PCL (intracapsular), MCL (extracapsular), LCL (extracapsular)
Shares joint space with the femoropatellar joint
Femoropatellar joint
Bony landmarks: patella (kneecap), femoral condyles
Cartilaginous structure: articular cartilage on the back of the patella and femoral surfaces
Reinforcing ligaments: patellar ligament, medial and lateral retinacula
Classification: synovial joint (plane/gliding)
Students often mix up structural and functional classification. A suture is structurally fibrous and functionally a synarthrosis – those are two separate labelling systems, not synonyms.
The knee is commonly called a hinge joint, but it is a modified hinge joint because it also permits some rotation. Exam questions may test this distinction.
Students frequently confuse abduction and adduction. A helpful mnemonic: abduction = moving away (ab = away), adduction = moving toward (add = adding back to the midline).
Flexion, extension, and hyperextension all happen in the sagittal plane. Students sometimes place abduction in the sagittal plane – it occurs in the frontal (coronal) plane.
⚠️ Be able to classify any joint by both its structural and functional type.
⚠️ Know the three subtypes of fibrous joints (sutures, syndesmoses, gomphoses) and where each is found.
⚠️ Distinguish synchondroses from symphyses by cartilage type and functional class.
⚠️ Know the six synovial joint types, their surface shapes, movements, and anatomical examples.
⚠️ For each named joint (sternoclavicular, glenohumeral, femorocoxal, femorotibular, femoropatellar), know the bony landmarks, cartilaginous structures, ligaments, and classification.
⚠️ The fibula is not directly involved in the knee joint – a commonly tested detail.
⚠️ Functional redundancy of nerves and blood vessels at joints is a concept that may appear as a short-answer question.
True or false: A gomphosis is found only in the skull.
Fill in the blank: Flexion, extension, and hyperextension all occur in the __________ plane.
True or false: All synovial joints are diarthrotic.
Fill in the blank: The __________ ligament is one of the strongest in the body and connects the ilium to the femur.
True or false: The fibula directly articulates with the femur at the knee joint.
Answers: 1. False (gomphoses are found between teeth and their sockets, not in the skull proper – sutures are skull-only). 2. Sagittal. 3. True. 4. Iliofemoral. 5. False.
Q: Name the three structural classes of joints and state what type of connective tissue binds the bones in each.
A: Fibrous joints (dense collagen fibres), cartilaginous joints (cartilage, either hyaline or fibrocartilage), and synovial joints (ligaments, with a synovial cavity present).
Q: What are the three types of reinforcing ligaments at synovial joints? Give an example of each.
A: Capsular (e.g. glenohumeral ligament), extracapsular (e.g. MCL or LCL of the knee), and intracapsular (e.g. ACL or PCL).
Q: Describe the structure of the synovial capsule, including both layers.
A: The outer fibrous layer is dense irregular CT proper that provides support and stability and is continuous with the periosteum. The inner synovial membrane is loose CT proper that secretes synovial fluid and covers bony surfaces inside the capsule not already covered by hyaline cartilage.
Q: A patient can flex and extend their thumb, and also abduct and adduct it, and can touch each fingertip with the thumb pad. What type of synovial joint allows all of these movements?
A: A saddle joint (the carpometacarpal joint of the thumb). The ability to touch fingertips specifically is the special movement called opposition.
Q: What is functional redundancy in the context of joint innervation and blood supply, and why is it important?
A: Functional redundancy refers to the overlapping presence of multiple nerve and blood vessel pathways at a joint. If one nerve or blood vessel is damaged, the joint retains function, sensory feedback, and healing capacity because the other pathways compensate.
Joint classification depends on the cartilage and connective tissue concepts from Chapter 6, so make sure those are solid. The movement terminology here (flexion, extension, abduction, adduction, rotation) is essential vocabulary for Chapters 10 and 11, where you will learn which muscles produce which movements at which joints. The specific joint anatomy (especially the knee and shoulder) is high-yield for clinical scenarios involving sprains, dislocations, and ligament tears.
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