8 Articulations

Section 1: Joint Design and Movement Learning Outcomes 8.1 Describe the basic structure of a synovial joint, and describe common accessory structures and their functions. 8.2 Explain the relationship between structure and function for each type of synovial joint. 8.3 Describe flexion/extension, abduction/adduction, and circumduction movements of the skeleton. 8.4 Describe rotational and special movements of the skeleton.

Section 1: Joint Design and Movement Articulations (joints) Where two bones interconnect Bones are relatively inflexible so necessary to allow movement Reflect compromise between need for strength versus need for mobility Anatomical structure of each joint determines type and amount of movement possible Categories from range of motion and subgroups from anatomical structure

Section 1: Joint Design and Movement Three functional categories Synarthrosis (no movement) Amphiarthrosis (little movement) Diarthrosis (free movement) Synarthrotic and amphiarthrotic joints Relatively simple structure Direct connections between bones Diarthrotic joints Complex in structure Permit greatest range of motion

Module 8.1: Synovial joints Components of synovial joints Articular cartilages Resemble hyaline cartilages Matrix contains more water comparatively Have no perichondrium Slick and smooth, so reduce friction Are separated by thin film of synovial fluid

Module 8.1: Synovial joints Components of synovial joints (continued) Synovial fluid Similar in composition to ground substance in loose connective tissues Produced at the synovial membrane Circulates from areolar tissue to joint cavity Percolates through articular cartilages Total quantity is less than 3 mL

Module 8.1: Synovial joints Components of synovial joints (continued) Joint capsule Dense and fibrous May be reinforced with accessory structures (tendons and ligaments) Continuous with periosteum of each bone

The structure of synovial joints Medullary cavity Periosteum Components of Synovial Joints Articular cartilage Joint capsule Synovial fluid Synovial membrane Spongy bone of epiphysis Figure 8.1.1 Synovial joints are freely movable diarthroses containing synovial fluid Compact bone Figure 8.1 1 8

Module 8.1: Synovial joints Functions of synovial fluid Lubrication With articular cartilage compression, synovial fluid is squeezed out and reduces friction between moving surfaces Nutrient distribution Provide nutrients and oxygen, as well as waste disposal for the chondrocytes of articular cartilages Compression and reexpansion of articular cartilages pump synovial fluid in and out of cartilage matrix Shock absorption Distributes compression forces across articular surfaces and outward to joint capsule

Module 8.1: Synovial joints Accessory structures Provide support and additional stability Not all are included in every joint Most are seen in the knee

Module 8.1: Synovial joints Accessory structures in knee Tendons of quadriceps Pass across joint Limit movement Provide mechanical support Bursa (a pouch) Small pocket filled with synovial fluid Often form in areas where tendon or ligament rubs against other tissues Reduce friction and act as shock absorbers

Module 8.1: Synovial joints Accessory structures in knee (continued) Fat pads Adipose tissue covered by synovial membrane Protect articular cartilages Act as packing material for joint Meniscus (a crescent) Pad of fibrous cartilage between bones of synovial joint May subdivide joint cavity and affect fluid flow or allow variations in shapes of articular surfaces

Module 8.1: Synovial joints Accessory structures in knee (continued) Accessory ligaments Support, strengthen, and reinforce joint Intrinsic ligaments Localized thickening of joint capsule Example: cruciate liagments of knee Extrinsic ligaments Separate from joint capsule May pass inside (intracapsular) or outside (extracapsular) the joint capsule Intracapsular example: cruciate ligaments Extracapsular example: patellar ligament

Accessory structures of complex synovial joints, as seen in a diagrammatic view of a sagittal section of the knee Tendon of the quadriceps muscles Patella Accessory Structures Synovial membrane Femur Bursa Joint capsule Fat pad Joint cavity Meniscus Articular cartilage Figure 8.1.3 Synovial joints are freely movable diarthroses containing synovial fluid Tibia Extracapsular ligament Intracapsular ligament Figure 8.1 3 14

Module 8.1: Synovial joints Mobility vs. strength in joints Greater range of motion = weaker joint Examples: Synarthrosis (strongest type of joint, no movement) Diarthrosis (far weaker but broad range of motion) Dislocation (luxation) Movement beyond normal range of motion Articulating surfaces forced out of position Can damage joint structures No pain from inside joint but from nerves or surrounding structures

Module 8.1 Review a. Define a joint dislocation (luxation). b. Describe the components of a synovial joint, and identify the functions of each. c. Why would improper circulation of synovial fluid lead to the degeneration of articular cartilages in the affected joint?

Module 8.2: Types of motion and structural types of synovial joints Types of motion permitted at synovial joints Gliding Movement along two axes in one plane Angular motion Movement along two axes in one plane with additional change in angle

Module 8.2: Types of motion and structural types of synovial joints Types of motion permitted at synovial joints (continued) Circumduction Special complex angular movement Proximal end of bone remains fixed while distal end can move in a circle (“trace circumference”) Rotation Bone ends remain fixed and shaft rotates Animation: Synovial Joints: Movement

The general types of movement at synovial joints Starting position Gliding Angular motion Figure 8.2.1-5 Anatomical organization determines the functional properties of synovial joints Circumduction Rotation Figure 8.2 1 – 5 19

The anatomical types of synovial joints, with joint models and examples Models of Joint Motion Examples Gliding joint • Acromioclavicular and claviculosternal joints Clavicle • Intercarpal and intertarsal joints Manubrium • Vertebrocostal joints • Sacro-iliac joints Hinge joint • Elbow joints Humerus • Knee joints • Ankle joints • Interphalangeal joints Ulna Pivot joint • Atlas/axis Atlas • Proximal radio-ulnar joints Axis Ellipsoid joint • Radiocarpal joints • Metacarpophalangeal joints 2–5 • Metatarsophalangeal joints Scaphoid bone Ulna Radius Figure 8.2.6 Anatomical organization determines the functional properties of synovial joints Saddle joint • First carpometacarpal joints Metacarpal bone of thumb Trapezium Ball-and-socket joint • Shoulder joints Scapula • Hip joints Humerus Figure 8.2 6 20

Module 8.2 Review a. Identify the types of synovial joints based on the shapes of the articulating surfaces. b. What type of synovial joint permits the widest range of motion? c. Indicate the type of synovial joint for each of the following: shoulder, elbow, ankle, and thumb.

Module 8.3: Specific angular movements Flexion and extension Usually applied to movements of long bones of limbs but also axial skeleton Flexion Anterior/posterior movement that reduces angle between articulating elements Lateral flexion Vertebral column bending to the side Dorsiflexion Flexion at ankle joint and elevation of sole Plantar flexion (planta, sole) Extension at ankle joint and elevation of heel

Module 8.3: Specific angular movements Flexion and extension (continued) Extension Anterior/posterior movement that increases angle between articulating elements Hyperextension Extension past anatomical position Animation: Foot Dorsiflexion: Plantar Flexion Animation: Elbow Flexion/Extension Animation: Wrist Flexion/Extension

Flexion and extension Extension Flexion Hyperextension Lateral flexion Dorsiflexion (ankle flexion) Flexion Extension Figure 8.3.1 Broad descriptive terms are used to describe movements with reference to the anatomical position Plantar flexion (ankle extension) Flexion Hyperextension Figure 8.3 1 24

Module 8.3: Specific angular movements Abduction and Adduction Always refers to movements of appendicular skeleton, not axial Movements are usually toward or away from body midline For fingers or toes, movements are spreading digits apart or bringing them together Abduction (ab, from) Movement away from body longitudinal axis in frontal plane Adduction (ad, to) Movement toward body longitudinal axis in frontal plane Animation: Humerus Abduction/Adduction

Abduction and adduction Figure 8.3.2 Broad descriptive terms are used to describe movements with reference to the anatomical position Abduction Adduction Figure 8.3 2 26

Module 8.3: Specific angular movements Circumduction Moving arm or thigh as if to draw a big circle at distal end of limb Animation: Wrist Circumduction Animation: Humerus Circumduction Animation: Synovial Joints: Angular Movement

Module 8.3 Review a. When doing jumping jacks, which lower limb movements are necessary? b. Which movements are associated with hinge joints? c. Compare dorsiflexion to plantar flexion.

Module 8.4: Rotation and special movements When applied to the trunk, described as left and right rotation When applied to limbs Medial rotation (internal or inward rotation) Anterior surface of limb toward trunk long axis Lateral rotation (external or outward rotation) Anterior surface of limb away from trunk long axis Animation: Humerus Rotation

Rotational movements Right rotation Left rotation Lateral (external) rotation Medial (internal) rotation Figure 8.4.1 Terms of more limited application describe rotational movements and special movements Figure 8.4 1 30

Module 8.4: Rotation and special movements Rotation (continued) Other special terms for rotation of forearm Pronation Proximal end of radius rotates near ulna Distal end rolls across anterior ulnar surface Turns the wrist and hand from palm facing front to palm facing back Supination Opposing movement Palm is turned anteriorly Animation: Elbow Pronation/Supination

Rotational movements Supination Pronation Figure 8.4.1 Terms of more limited application describe rotational movements and special movements Supination Pronation Figure 8.4 1 32

Module 8.4: Rotation and special movements Opposition Movement of thumb toward palm surface or other fingers Protraction Movement forward in anterior plane Retraction Reverse of protraction Inversion (in, into + vertere, to turn) Twisting foot motion to turn sole inward Eversion (e, out) Opposing movement to inversion

Module 8.4: Rotation and special movements Special movements (continued) Depression Movement inferiorly Elevation Movement superiorly Animation: Foot Inversion/Eversion Animation: Hand Opposition

Special movements Opposition Retraction Protraction Figure 8.4.2 Terms of more limited application describe rotational movements and special movements Eversion Inversion Depression Elevation Figure 8.4 2 35

Module 8.4 Review a. Snapping your fingers involves what movement with the thumb and third metacarpophalangeal joint? b. What movements are made possible by the rotation of the radius head? c. What hand movements occur when wriggling into tight-fitting gloves?

Section 2: Articulations Learning Outcomes 8.5 Describe the articulations between the vertebrae of the vertebral column. 8.6 Describe the structure and function of the shoulder and hip joints. 8.7 Describe the structure and function of the elbow and knee joints. 8.8 CLINICAL MODULE Explain arthritis, and describe its effects on joint structure and function.

Section 2: Articulations Axial skeleton articulations Typically are strong but very little movement Appendicular skeleton articulations Typically have extensive range of motion Often weaker than axial articulations

Joints of the Axial Skeleton Sutures of the skull Temporomandibular joint (temporal bone and mandible) Atlanto-occipital joint (occipital bone and atlas) and the atlanto-axial joint (C1–C2) Joints of the thoracic cage Intervertebral joints Figure 8 Section 2 Articulations of the Axial and Appendicular Skeletons The lumbosacral joint, which attaches the last lumbar vertebra to the sacrum The sacrococcygeal and intercoccygeal joints, which structurally resemble simplified intervertebral joints Figure 8 Section 2 1 39

Joints of the Appendicular Skeleton The sternoclavicular joint, the only articulation between the axial skeleton and the pectoral girdle and upper limb Shoulder joint The sacro-iliac joint, which firmly attaches the sacrum of the axial skeleton to the pelvic girdle of the appendicular skeleton Elbow joint Superior and inferior radio-ulnar joints Pubic symphysis Wrist joint Joints of the hand and fingers Hip joint Figure 8 Section 2 Articulations of the Axial and Appendicular Skeletons Knee joint Ankle joint Joints of the foot and toes Figure 8 Section 2 2 40

Module 8.5: Vertebral articulations Between superior and inferior articular processes of adjacent vertebrae Gliding diarthrotic joints Permit flexion and rotation Adjacent vertebral bodies form symphyseal joints with intervertebral discs Numerous ligaments attach bodies and processes of vertebrae to stabilize column 41

Module 8.5: Vertebral articulations Intervertebral discs Composition Anulus fibrosis Tough outer layer of fibrous cartilage Collagen fibers attach to adjacent vertebrae Nucleus pulposus Soft, elastic, gelatinous core Provides resiliency and shock absorption Account for ¼ length of vertebral column Water loss from discs causes shortening of vertebral column with age and increases risk of disc injury 42

An intervertebral disc Anulus fibrosus Nucleus pulposus Figure 8.5.1 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies Superior view Figure 8.5 1 43

Module 8.5: Vertebral articulations Primary vertebral ligaments Ligamentum flavum Connects adjacent vertebral laminae Posterior longitudinal ligament Connects posterior surfaces of adjacent vertebral bodies Interspinous ligament Connects spinous processes of adjacent vertebrae Supraspinous ligament Connects spinous processes from sacrum to C7 Ligamentum nuchae from C7 to base of skull Anterior longitudinal ligament Connects anterior surfaces of adjacent vertebral bodies 44

Primary Vertebral Ligaments The ligaments attached to the bodies and processes of all vertebrae Primary Vertebral Ligaments Ligamentum flavum Intervertebral disc Anulus fibrosus Posterior longitudinal ligament Nucleus pulposus Spinal cord Interspinous ligament Spinal nerve Supraspinous ligament Posterior longitudinal ligament Figure 8.5.2 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies Anterior longitudinal ligament Lateral view Sectional view Figure 8.5 2 45

Module 8.5: Vertebral articulations Disorders of vertebral column Slipped disc Posterior longitudinal ligaments weaken causing more pressure on discs Nucleus pulposus compresses, distorts anulus fibrosus Disc bulges into vertebral canal (doesn’t actually slip) Herniated disc Nucleus pulposus breaks through anulus fibrosus Spinal nerves are often affected 46

A slipped disc, as seen in a lateral view Normal intervertabral disc L1 Slipped disc Figure 8.5.3 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies L2 Figure 8.5 3 47

A herniated disc, as seen in a superior view Compressed area of spinal nerve Spinal nerve Figure 8.5.4 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies Spinal cord Nucleus pulposus of herniated disc Anulus fibrosis Figure 8.5 4 48

Module 8.5: Vertebral articulations Disorders of vertebral column (continued) Osteopenia (penia, lacking) Inadequate ossification leading to loss of bone mass Often occurs with age beginning between ages 30 and 40 More severe in women than men Osteoporosis (porosus, porous) Bone loss sufficient to affect normal function 49

The effects of osteoporosis on spongy bone Figure 8.5.5 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies Clinical scan of a compression fracture in a lumbar vertebra Figure 8.5 5 50

The effects of osteoporosis on spongy bone Figure 8.5.5 Adjacent vertebrae have gliding diarthroses between their articular processes, and symphyseal joints between their vertebral bodies Normal spongy bone SEM x 25 Spongy bone with osteoporosis SEM x 21 Figure 8.5 5 51

Module 8.5 Review a. Identify the primary vertebral ligaments. b. Describe the nucleus pulposus and anulus fibrosus of an intervertebral disc. c. Compare a slipped disc with a herniated disc. 52

Module 8.6: Shoulder and hip joints Shoulder joint (glenohumeral joint) Greatest range of motion of any joint Most frequently dislocated joint Demonstrates stability sacrificed for mobility Most stability provided by surrounding skeletal muscles, associated tendons, and various ligaments Ball-and-socket diarthrosis Formed by head of humerus and glenoid cavity of scapula Socket of glenoid cavity increased by fibrous-cartilaginous glenoid labrum (labrum, lip or edge) Animation: Scapula Clavicle Humerus 53

Module 8.6: Shoulder and hip joints Shoulder joint (continued) Ligaments stabilizing the shoulder Coracoclavicular ligaments Acromioclavicular ligament Coraco-acromial ligament Coracohumeral ligament Glenohumeral ligaments 54

The shoulder joint (glenohumeral joint) Coracoid process Clavicle Acromion Ligaments Stabilizing the Shoulder Bursae Coracoclavicular ligaments Articular capsule Acromioclavicular ligament Figure 8.6.1 The shoulder and hip are ball-and-socket joints Scapula Coraco-acromial ligament Tendon of the biceps brachii muscle Coracohumeral ligament Glenohumeral ligaments Humerus Figure 8.6 1 55

The structures within and surrounding the shoulder joint A frontal section of the shoulder joint A lateral view of the shoulder joint Subdeltoid bursa Articular capsule Coraco-acromial ligament Coracoclavicular ligaments Acromioclavicular ligament Clavicle Tendon of supraspinatus muscle Clavicle Acromion Tendon of infraspinatus muscle Tendon of biceps brachii muscle Coracohumeral ligament (cut) Articular cartilages Articular capsule Glenoid cavity Humerus Scapula Glenohumeral ligaments Subscapularis muscle Glenoid labrum Glenoid labrum Figure 8.6.2-3 The shoulder and hip are ball-and-socket joints Teres minor muscle Scapula Synovial membrane Frontal section Lateral view Figure 8.6 2 – 3 56

Module 8.6: Shoulder and hip joints Sturdy ball-and-socket joint Although not directly aligned with weight distribution along femur shaft, which can produce fractures of femoral neck or intertrochanteric region Permits flexion, extension, adduction, abduction, circumduction, and rotation Formed by head of femur and acetabulum of hip bone Socket of acetabulum increased by projecting rim of fibrous cartilage (acetabular labrum) Articular capsule extends from lateral/inferior surfaces of pelvic girdle to intertrochanteric line and crest of femur 57

The hip joint in lateral view Iliofemoral ligament Fibrous cartilage pad Acetabular labrum Fat pad Acetabulum Ligamentum teres (ligament of the femoral head) Figure 8.6.4 The shoulder and hip are ball-and-socket joints Transverse acetabular ligament Figure 8.6 4 58

Module 8.6: Shoulder and hip joints Hip joint (continued) Reinforcing ligaments Transverse acetabular ligament Crosses acetabular notch, filling gap in inferior border Ligamentum teres (teres, long and round) Originates along transverse acetabular ligament and attached to fovea capitis Pubofemoral ligament Iliofemoral ligament Ischiofemoral ligament Animation: Pelvic Girdle: Hip Femur 59

Reinforcing Ligaments Ischiofemoral ligament The ligaments of the hip joint Reinforcing Ligaments Pubofemoral ligament Iliofemoral ligament Ischiofemoral ligament Greater trochanter Ischial tuberosity Posterior view Inter- trochanteric line Figure 8.6.5 The shoulder and hip are ball-and-socket joints The ligaments of the hip joint in posterior view Lesser trochanter Anterior view The ligaments of the hip joint in anterior view Figure 8.6 5 60

Module 8.6 Review a. Which tissues or structures provide most of the stability for the shoulder joint? b. At what site are the iliofemoral ligament, pubofemoral ligament, and ischiofemoral ligament located? c. A football player received a hard tackle to the upper surface of his shoulder, causing a shoulder separation. What bones and ligaments would be affected? 61

Module 8.7: Elbow and knee joints Elbow joint Complex hinge joint involving humerus, radius, and ulna Extremely strong and stable due to: Bony surfaces of humerus and ulna interlock Single, thick articular capsule surrounds both humero-ulnar and proximal radio-ulnar joints Articular capsule reinforced by strong ligaments Severe stresses can still produce dislocations or other injuries Example: nursemaid’s elbow Muscles flexing elbow attach on anterior while those extending attach on the posterior 62

Module 8.7: Elbow and knee joints Elbow joint (continued) Specific joints of the elbow Humeroradial joint Capitulum of humerus articulating with head of radius Humero-ulnar joint Largest and strongest articulation Trochlea of humerus articulates with trochlear notch of ulna Shape of ulnar notch determines plane of movement Shapes of olecranon fossa and olecranon limit degree of extension Proximal radio-ulnar joint is not part of elbow joint 63

The elbow joint Anterior view Humeroradial joint Humerus Humeroulnar joint Figure 8.7.1 The elbow and the knee are hinge joints Radius Ulna Proximal radio-ulnar joint (not part of the elbow joint) Figure 8.7 1 64

Module 8.7: Elbow and knee joints Elbow joint (continued) Reinforcing ligaments Radial collateral ligament Stabilizes lateral surface of joint Ulnar collateral ligament Stabilizes medial surface of joint Annular ligament Binds head of radius to ulna 65

The elbow joint Posterior view Humerus Olecranon fossa Humeroulnar joint Figure 8.7.1 The elbow and the knee are hinge joints Ulna Olecranon Figure 8.7 1 66

Module 8.7: Elbow and knee joints Contains three separate articulations Medial condyle of tibia to medial condyle of femur Lateral condyle of tibia to lateral condyle of femur Patella and patellar surface of femur Permits flexion, extension, and very limited rotation Animation: Patella Tibia Fibula 67

Module 8.7: Elbow and knee joints Knee joint (continued) External support Quadriceps tendon to patella Continues as patellar ligament to anterior tibia Fibular collateral ligament Lateral support Tibial collateral ligament Medial support Popliteal ligaments Posterior support extending between femur and heads of tibia and fibula Tendons of several muscles that attach to femur and tibia 68

The knee joint Superficial Superficial anterior view posterior view Femur Quadriceps tendon Joint capsule Fibular collateral ligament Bursa Patella Tibial collateral ligament Fibular collateral ligament Cut tendon of biceps femoris muscle Patellar ligament Popliteal ligaments Tibia Figure 8.7.3-4 The elbow and the knee are hinge joints Fibula Fibula Tibia Figure 8.7 3 – 4 69

Module 8.7: Elbow and knee joints Knee joint (continued) Internal support Cruciate ligaments limit anterior/posterior movement of femur and maintain alignment of condyles Anterior cruciate ligament (ACL) At full extension, knee becomes “locked” (slight lateral rotation tightens ACL, and lateral meniscus forced between tibia and femur) Opposite motion to “unlock” Posterior cruciate ligament (PCL) 70

Module 8.7: Elbow and knee joints Knee joint (continued) Internal support (continued) Medial and lateral menisci Fibrous cartilage pads between tibial and femoral condyles Act as cushions and provide lateral stability to joint 71

The knee joint Deep anterior Deep posterior view, flexed view, extended PCL ACL Patellar surface of femur ACL PCL Femur Fibular collateral ligament Lateral condyle Medial condyle Fibular collateral ligament Medial condyle Lateral condyle Tibial collateral ligament Tibia Medial and lateral menisci Tibia Fibula Figure 8.7.3-4 The elbow and the knee are hinge joints Fibula Figure 8.7 3 – 4 72

Module 8.7 Review a. Between the elbow and knee joints, which have menisci? b. What signs and symptoms would you expect in an individual who has damaged the menisci of the knee joint? 73

CLINICAL MODULE 8.8: Disruption to normal joint function Arthritis Damage to articular cartilages but specific cause varies Exposed surfaces change from slick, smooth-gliding to rough feltwork of collagen fibers increasing friction Rheumatism (pain and stiffness affecting the skeletal and/or muscular systems) is often a symptom Osteoarthritis Also known as degenerative arthritis or degenerative joint disease Generally affects individuals age 60 and older 25% of women, 15% of men Can result from cumulative wear and tear of joints or genetic factors affecting collagen formation 74

Normal Joint Arthritic Joint Comparisons of normal articular cartilage with articular cartilage damaged by osteoarthritis Normal Joint Arthritic Joint Fibrous remains of the articular cartilage Articular cartilage Degenerating articular cartilage LM x 180 LM x 180 Figure 8.8.1-2 Arthritis can disrupt normal joint structure and function Arthroscopic view of normal cartilage Arthroscopic view of damaged cartilage Figure 8.8 1 – 2 75

CLINICAL MODULE 8.8: Disruption to normal joint function Visualizing problematic joints Arthroscopic surgery Optical fibers (arthroscope) inserted into joint through small incision without major surgery to visualize joint interior If necessary, other instruments can be inserted through other incisions to permit surgery within view of arthroscope Magnetic resonance imaging Cost-effective and noninvasive viewing technique that allows examination of soft tissues around joint as well 76

An arthroscopic view of the interior of the left knee, showing injuries to the anterior and posterior cruciate ligaments. PCL Femoral condyle ACL Meniscus Figure 8.8.3 Arthritis can disrupt normal joint structure and function Figure 8.8 3 77

Figure 8.8.4 Arthritis can disrupt normal joint structure and function 78

CLINICAL MODULE 8.8: Disruption to normal joint function Artificial joints May be last resort if other solutions (exercise, physical therapy, drugs) for joint problems fail Not as strong as natural joints, so most suitable for elderly Typically have service life of about 10 years 79

Figure 8.8.5 Arthritis can disrupt normal joint structure and function 80

CLINICAL MODULE 8.8 Review a. Compare rheumatism to osteoarthritis. b. Explain the use of an arthroscope. c. What can a person do to slow the progression of arthritis? 81