Danika Lehmann BSc MSc BN RN

March 19, 2011

  Joint anatomy & function

  Pathophysiology of osteoarthritis

  Treatment & management of osteoathritis

  Specific examples

  Articular cartilage   Subchondral bone   Synovial membrane   Synovial fluid   Joint capsule   Ligaments

  Intrasynovial   Extrasynovial

  Connective tissue forming glassy-smooth covering on surface of synovial joint

  Only a few millimeters thick

  Load transmission & friction reduction

  Consists of cells suspended in matrix

  Devoid vascular, lymphatic, & neural connections

  Chondrocytes (cells)   Production & maintenance of cartilage   Synthesis of collagens, proteoglycans, and other

macromolecules

  Extracellular matrix (gelatinous fluid)   Products of chondrocytes   Water

  Zonal organization from surface to depth:

Articular Cartilage and Osteoarthritis (1992).

  Negatively charged matrix = swelling pressure

  Resistance to compression during load

  Tissue deformation & expulsion of water lead to greater resistance to further deformation

  Equilibrium: external loading force = internal swelling pressure

Buckwalter Articular Cartilage & Knee Joint Function 1990 Maroudas J Orthop Res 1987

  Connective tissue forming rigid skeletal frame

  Cortical (compact)

  Cancellous (spongy or trabecular)

  Trabeculae aligned to resists stress/strain

  Subchondral bone plate = calcified cartilage + tidemark

Subchondral bone plate

Subchondral trabecular bone

Epiphyseal scar

  Cells:   Osteoblasts – producers   Osteocytes – communicators   Osteoclasts – destructors   Periosteal cells – vascular/nerve supply

  90-95% collagen fibers

  Ground substance

  Major mineral reservoir of calcium & phosphate

  Hydroxyapatite = crystalline salt for structural rigidity

  Magnesium, sodium, potassium, carbonate

Vigorita Orthopaedic Pathology 1999 Guyton Textbook of Medical Physiology 1996

  Collagen fibers tensile strength

  Crystalline salts compressional strength

  Strength correlated with:   Trabecular architecture   Bone mineral density   Crystal number   Crystal size   Crystal distribution

Landis Bone 1995 Buckwalter Instr Course Lect 1996

  Concept of bone plasticity

  Bone deposition = resorption

  Physiological importance: 1.  Bone adjusts strength in proportion to stress 2.  Rearrangement of shape for proper support 3.  Brittle, weak bone replaced with new

Rubin Rheum Dis Clin North Am 1988

  “Synovium”

  1 - 4 cells thick lining joint capsule

  Produces synovial fluid to lubricate joint & reduce friction

  Rheumatic disease responsible for deterioration of articular cartilage, subchondral bone, and synovium

Destruction and failure of synovial joints

Sangha J Rheumatol Suppl 2 2000

  “…a group of overlapping diseases, which may have different aetiologies but with similar biologic, morphologic, and clinical outcomes. The disease process not only affects the articular cartilage, but involves the entire joint, including the subchondral bone, ligaments, capsule, synovial membrane, and periarticular muslces.”

American Academy of Orthopaedic Surgeons 1994

  Aetiology largely unknown

  Theories: 1.  Biomechanical

  Joint fracture   Ligament damage   Joint laxity   Injury/trauma   Obesity

2.  Biochemical   Water   Proteoglycan type, size, aggregation

Brandt J Rheumatol 1986

  Stages:

1.  Disruption of cartilage matrix

2.  Response to tissue damage

3.  Failure of repair process

Mankin N Engl J Med 1974 Cohen J Orthop Sports Phys Ther 1998

  Stage 1: Disruption of cartilage matrix   Water retention   Decrease cartilage resilience & stiffness   Fibrillation (“cut velvet”)

  Stage 2: Response to tissue damage   Damaged matrix cleared   Repair initiated

  Stage 3: Failure of the repair process   Decrease repair response   Progressive loss of cartilage, splits, craters   Awry!

Full thickness cartilage loss 12wks post-trauma (a) femur, (b) tibia, (c) trochlea.

MRI of stifle joint showing progressive cartilage loss post-trauma.

  Failure of cartilage repair process ??

  Damage or death of chondrocytes from mechanical stress & lack of protection by functional matrix?

  Synthesis & accumulation of matrix molecules that inhibit repair process?

Buckwalter Articular Cartilage & Knee Joint Function 1990

  Cartilage changes cannot be dissociated from subchondral bone changes

  Highly debated whether bone changes precede, are concurrent with, or succeed articular cartilage changes

Dequeker Microsc Res Tech 1997 Radin Clin Orthop 1986

  Hypermetabolic state:   Increased bone mineral density (sclerosis)   Formation of microcysts   Osteophytes

  Osteoarthritic bone remodeling:   Greater subchondral stiffness & rigidity   Decreased ability to respond to loading & compression   Greater stress & strain on articulating surface   Greater mechanical load that cartilage must bear

  Complete cartilage degeneration   Deformity, shortening of limb, instability, joint pain

Fazzalari Bone 1998

  Clinical history

  X-rays

  Arthroscopy

  Joint pain & tenderness

  Crepitus, limitation in movement

  Occasional effusion (excess fluid) with variable degrees of inflammation

  No systemic effects

  Loss of joint space = loss of cartilage

  Increase in subchondral bone opacity = sclerosis

Irreversible damage!

Radiograph of normal joint Radiograph of OA joint

Joint space

Sclerosis & loss of joint space

  Type & severity of joint damage

  Many drugs to ease pain, discomfort, swelling, & manage inflammation:   Steroids   NSAIDS   DMSO   Glucosamine   Hyaluronate   PSGAGs

* These drugs DO NOT stop or reverse the osteoarthritic process *

  “Corticosteroids” or “glucosteroids”   E.g., dexamethasone, methylprednisolone,

tramcinolone acetate   Often via intra-articular injection   Manage pain & inflammation

  Side Effects:   Laminitis   Further damage by stopping/delaying anabolic

process?

Labens Vet Rec 2007

  “NSAIDs”   E.g., phenylbutazone, naproxen, flunixin

meglumine, diclofenac   Various routes of administration   Manage pain & inflammation

  Side effects:   Stomach ulcers, bleeding, slowing of healing process

  “DMSO”   Topical drug to control inflammation & swelling   Organic solvent has ability to carry other drugs

through skin

  Side effects:   Cataracts in dogs…long-term use in horses?   Organic solvent - wear rubber or latex gloves

  Precursor in building connective tissue   E.g., glucosamine sulfate or hydrochloride,

Cosequin (glucosamine + chondroitin)   Oral supplement; sulfate easiest to absorb &

essential for connective tissue   Efficacy?

  Side effects:   ?

Pearson Equine Vet J 2009

  E.g., Legend®   Intravenous or intra-articular injection   Manage inflammation & increase quality of

synovial fluid

  Side effects:   IV – depression, lethargy, fever   IA – lameness, joint effusion, joint or injection site

swelling, joint pain, severe inflammatory reaction, joint sepsis

Frisbie Am J Vet Res 2009, Palmieri Acta Biomed 2010, Mouzopoulos Minerva Med 2011, Kuemmerle Vet Comp Orthop Traumatol 2006

  “PSGAGs” or “GAGs”   E.g., Adequan®   Often multiple intramuscular injections   Manage inflammation, synovial fluid effusion,

synovial membrane vascularity/fibrosis

  Side effects:   ?

Frisbie Am J Vet Res 2009, Gaustad Equine Vet J 1995, Todhunter Vet Surg 1993

  Exercise   Maintains or improves strength of peri-articular

structures (muscles, ligaments, tendons)   Decreases bone loss resulting from inactivity   Controls joint swelling, stiffness & pain   Improves joint ROM   Replenishes synovial fluid   Enhances energy & stamina   Decreases anxiety   Improves mood & well-being   Promotes state of relaxation

Minor Rheum Dis Clin North Am 1999

  Goals of an exercise program:

  Preserve or restore ROM & flexibility around joint

  Increase muscle strength & endurance

  Increase aerobic conditioning to improve health, mood & decrease health risks associated with sedentary lifestyle

  Exercise program can be organized as follows:

  Serous athritis

  Septic arthritis

  Bone spavin

  Osselets

  Omarthritis

  “Acute synovitis”   Swollen, tender, fluid-filled joint   Joint stress or injury   Does not necessarily progress to OA

  Tx:   Rest & application of cold or hot/cold therapy   Veterinary recommended medications   Corrective shoeing

  “Infectious arthritis”   Bacterial infection of the joint   Often causes irreversible damage, progressing

to OA

  Tx:   Immediate veterinary attention   Broad-spectrum antibiotics, joint aspiration & C&S

  “Jack spavin”, osteoarthritis of the hock joint   Caused by hard use or poor conformation   Pain concentrated to inside of hock   May begin as a cold lameness

  Tx:   Discontinue stressful activity   Medication to manage pain & inflammation   Corrective shoeing   Surgery (in advanced cases)

  Osteoarthritis of the fetlock   Chronic stress injury from repeated concussion   “Green” = acute synovitis   “True” = osteoarthritis

  Tx:   Green – same as acute synovitis   True – symptomatic relief

  Osteoarthritis of the shoulder (usually 2° to #)   Shoulder joint lameness, swelling, tenderness   Nerve block, x-rays, arthroscopy helpful for Dx

  Tx:   Veterinary attention   Surgery & medications