Osteoarthritis
'I have fallen, and I can't get up"
Articular (hyaline) cartilage in the synovial joints breaks down and causes pain, swelling, and restricts movement of joints
Osteoarthritis predominantly involves the weight-bearing joints, including the knees, hips, cervical and lumbosacral spine, and feet
Other commonly affected joints include the distal interphalangeal (DIP), proximal interphalangeal (PIP), and carpometacarpal (CMC) joints
Primary
Related to the aging process and typically occurs in older individuals, it is an idiopathic phenomenon, occurring in previously intact joints and having no apparent initiating factor
NOTE: the term primary, or idiopathic, osteoarthritis may become obsolete…many investigators believe that most cases of primary osteoarthritis of the hip may, in fact, be due to subtle or even unrecognizable congenital or developmental defects.
Secondary
Disease of the synovial joints that results from some predisposing condition that has adversely altered the joint tissues (eg, trauma to articular cartilage or subchondral bone). Secondary osteoarthritis can occur in relatively young individuals
In early osteoarthritis
Swelling of the cartilage usually occurs, because of the increased synthesis of proteoglycans; this reflects an effort by the chondrocytes to repair cartilage damage.
This stage may last for years or decades and is characterized by hypertrophic repair of the articular cartilage
As osteoarthritis progresses
The level of proteoglycans eventually drops very low, causing the cartilage to soften and lose elasticity and thereby further compromising joint surface integrity.
Microscopically, flaking and fibrillations (vertical clefts) develop along the normally smooth articular cartilage on the surface of an osteoarthritic joint.
Over time, the loss of cartilage results in loss of joint space
Erosion of the damaged cartilage in an osteoarthritic joint
progresses until the underlying bone is exposed. Bone denuded of its protective cartilage continues to articulate with the opposing surface.
Eventually, the increasing stresses exceed the biomechanical yield strength of the bone. The subchondral bone responds with vascular invasion and increased cellularity, becoming thickened and dense
The traumatized subchondral bone may also undergo cystic degeneration
Osteoarthritic cysts are also referred to as subchondral cysts, pseudocysts, or geodes and may range from 2 to 20 mm in diameter.
Osteoarthritic cysts in the acetabulum are termed Egger cysts
Osseous metaplasia of synovial connective tissue, and ossifying cartilaginous protrusions
Lead to irregular outgrowth of new bone (osteophytes)
Fragmentation of these osteophytes or of the articular cartilage itself results in the presence of intra-articular loose bodies (joint mice)
Along with joint damage
Osteoarthritis may also lead to pathophysiologic changes in associated ligaments and the neuromuscular apparatus
Mechanisms that occur within this disease
- Osteophytic periosteal elevation
- Vascular congestion of subchondral bone, leading to increased intraosseous pressure
- Synovitis with activation of synovial membrane nociceptors
- Fatigue in muscles that cross the joint
- Overall joint contracture
- Joint effusion and stretching of the joint capsule
- Torn menisci
- Inflammation of periarticular bursae
- Periarticular muscle spasm
- Psychological factors
- Crepitus (a rough or crunchy sensation)
- Central pain sensitization
Interleukin-1 causes chondrocytes and synovial cells and synthesis of matrix metalloproteinases, which are responsible for the degradation of cartilage
- Abnormal integrin expression alters cell/ECM signaling and modifies chondrocyte synthesis, with the following imbalance of destructive cytokines over regulatory factors.
- IL-1, TNF-alpha and other pro-catabolic cytokines activate the enzymatic degradation of cartilage matrix and are not counterbalanced by adequate synthesis of inhibitors
1 out of 2 adults
1 out of 4 adults
1 in 12 people
Age
- Reduction in cartilage volume, proteoglycan content, cartilage vascularization and cartilage perfusion
- Narrowed joint space
- Not enough on its own to cause OA
- > 65 y/o
Obesity
- Increase in mechanical stress in weight-bearing joints
- Inflammatory risk (adipokines - cytokines derived from adipose tissue)
- Trauma
- Abnormal biomechanics
- Muscle dysfunction compromises neuromuscular protective mechanisms leading to increased joint motion and OA
Genetics
- Genes: ADAM12, CLIP, IL10, and MMP3 lead to differential methylation leading to collagen degradation
- COL1A2 mutations lead to early onset OA
- MCF2L is key in neutrophin-mediated regulation of peripheral nervous system cell motility
- Heritability
- Reduced levels of sex hormones
- Muscle weakness
- Repetitive use
- Infection
- Crystal deposition
- Acromegaly
- Previous inflammatory arthritis
- Heritable metabolic causes (Wilson Disease, hemochromatosis)
- Hemoglobinopathies (Sickle Cell Disease, thalassemia)
- Neuropathic disorders leading to a Charcot joint
- Underlying morphologic risk factors (congenital hip dislocation)
- Disorders of bone (Paget Disease)
- Previous surgical procedures
- > 55 y/o, women are at a higher risk than men
- Native Americans are at higher risk than another other population
- Whites more common than blacks
Diagnostics (labs, testing, screening)
· Differentiate osteoarthritis from others, such as rheumatoid arthritis
· History and physical exam is sufficient to diagnose osteoarthritis
· Radiographs confirm the initial impression and laboratory values
· No specific laboratory abnormalities are associated with OA
· No single biomarker has proved reliable for diagnosis and monitoring, but
combinations of cartilage-derived and bone-derived biomarkers have been used to
identify OA subtypes
Plain radiographs is the imaging method of choice
MRI
Can be used since it can detect the same thing a plain radiograph can, but it is not used unless additional pathology amenable to surgical repair is suspected
Pathologies include: joint narrowing, subchondral osseous changes, and osteophytes
Can directly visualize articular cartilage and other joint tissues
Bone scanning
GOAL: Alleviation of pain and improvement of functional status
Nonpharmacologic interventions
Patient education
Heat and cold
Weight loss
Exercise
- Cardiovascular or resistance land-based exercise
- Aquatic exercise
- Tai chi
Physical therapy
Occupational therapy
Unloading in certain joints
Assistive devices
Acupuncture
Surgery
- Athroscopy, osteotomy, and arthroplasty
Fusion and Joint Lavage
Pharmacologic interventions
- Topical capsaicin
- Topical / Oral NSAIDs
- Tramadol
- Acetaminophen
- Intra-articular corticosteroid injections
- Opioids
- Pain patches
- Growth factor injections
- Duloxetine (selective serotonin-norepinephrine reuptake inhibitor)
- Skeletal muscle relaxants
*Vary depending on the joint(s) effected*
Worse after activity or toward end of day
Tenderness
Stiffness
First thing in the morning or after rest
Loss of flexibility
Grating sensation (crepitus)
Bone spurs
Effected joints get swollen, especially after extended activity
Areas
Hips
Pain is felt in groin area or buttocks and sometimes inside knee or thigh
Knees
A “grating/scraping” sensation occurs when moving knees
Fingers
Bony growth (spurs) at edge of joints. Causes swelling, tenderness, and redness. Pain at the base of thumb.
Feet
Pain and tenderness felt in large joint at base of big toe. Swelling in ankles or toes.
Upper extremities
Pain, swelling, stiffness may make ordinary tasks very difficult (ex. Making bed, opening box of food, using computer mouse, driving car, writing, holding/grasping items).
Lower extremities
Pain, swelling, stiffness may make ordinary tasks very difficult (ex. Walking, climbing stairs, lifting objects)
NOTE
References
Arthritis Foundation. (2015). Osteoarthritis. Retrieved from http://www.arthritis.org/about-arthritis/types/osteoarthritis/what-is-osteoarthritis.php
Expanscience Laboratories. (2015). Osteoarthritis. Retrieved from http://www.arthrolink.com/en/disease/understanding/mechanisms-osteoarthritis
Lozada. C. (2015, March 27). Osteoarthritis. Retrieved from http://emedicine.medscape.com/article/330487-overview
The Mayo Clinic Staff. (2014, Oct 9). Disease and Conditions: Osteoarthritis. Retrieved from http://www.mayoclinic.org/diseases-conditions/osteoarthritis/basics/definition/con-20014749
Osteoarthritis. (n.d.). Retrieved December 1, 2015, from https://youtu.be/41IMR_Dp5bs
Osteoarthritis gene therapy being developed at UF could help both people, animals. (n.d.). Retrieved December 1, 2015, from https://youtu.be/WCfck1H_b_U
Euflexxa knee injection animation. (n.d.). Retrieved December 1, 2015, from https://youtu.be/Sa_-NSByo-0
Jamie Oliver - TED Talk on Obesity and Food. (n.d.). Retrieved December 1, 2015, from https://youtu.be/wOPl8P2S-Lw
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