Pathophysiology of Osteoarthritis
Pathophysiology of Osteoarthritis
Osteoarthritis (OA) is a common age-related disorder of synovial joints. One may know OA by “degenerative joint disease” or “joint wear and tear.” OA is characterized by loss of articular cartilage, inflammation, formation of osteophytes, synovitis, and subchondral bone changes (Huether & McCance, 2017). OA commonly affects hands, wrists, knees, feet, hips, shoulders, and spine. OA prevalence increases with age and women generally have worse symptoms. Obesity and trauma are risk factors (Huether & McCance, 2017). Researchers believe that gene expression in chondrocytes affect the incidence of OA (Huether & McCance, 2017). The regulatory action of the proteoglycan pump of cartilage cells is disrupted, and they take in too much water. Increased water content lessens cartilage’s ability to tolerate weightbearing (Huether & McCance, 2017). The breakdown of articular cartilage causes cracks and fissures, leading to osteophytes, inflammation, synovitis, and joint effusion (Huether & McCance, 2017). Pain with weightbearing is the most common symptom. Symptoms can also include stiffness, swelling, limited range of motion, and deformity (Huether & McCance, 2017).
Pathophysiology of Rheumatoid Arthritis
Another condition that involves synovial joints is rheumatoid arthritis (RA). RA is chronic, systemic, and inflammatory. It leads to disability and premature death (Huether & McCance, 2017). In RA, synovial fibroblasts develop an exaggerated immune response and proliferate abnormally, as well as produce cytokines, enzymes, and prostaglandins (Huether & McCance, 2017). The thickened synovium is called “pannus” and invades the surrounding bone, ligaments, and tendons, causing pain and deformity (Huether & McCance, 2017). RA most commonly affects the fingers, feet, wrists, elbows, ankles, and knees. The lungs, heart, kidneys, and skin can also be involved (Huether & McCance, 2017).
Similarities and Differences
Both OA and RA result in joint pain and deformity. However, their pathophysiology and disease progressions are markedly different. OA can be present in just one joint. RA is a systemic inflammatory disease that affects multiple joints and possibly organs. OA has a slow onset as the cartilage wears away, occurring over years. In contrast, because RA is inflammatory, it can cause pain within a few weeks or months (Harvard Medical School, n.d.). Pain with OA is generally caused by the inflammation caused by the structural cellular changes, whereas RA pain is caused by both destructive changes and the presence of inflammation from the immune response. There are differences in treatment, but both OA and RA can be treated by intra-articular steroid injections, physical and occupational therapy, and joint replacement.
Impact of Age and Behavior
The incidence of both RA and OA increase with age. Treatment for severe OA and RA may be limited depending on the age of the patient. Patients are having total joint replacements at younger and younger ages. The younger the person is, the more likely they will need a revision down the road due to implant loosening and infection because of the sheer length of time they will live with their total joint (Rath, n.d.). Although there is no specific guideline on the appropriate age of a patient, orthopedic surgeons are generally hesitant to give younger patients a total joint. It is recommended they live with the arthritis for as long as they can. In addition, age can be a limiting factor for surgery for the elderly. To prepare for Medicare bundled payments for total joint arthroplasty, facilities should practice risk stratification (Courtney et al., 2018). Therefore, access to arthroplasty may be more and more limited for the older, sicker population.
Smoking and diet are modifiable risk factors identified for RA (Huether & McCance, 2017). Obesity and activities that put a great amount of stress on joints (such as long distance running, and high impact sports) are behavioral factors that influence OA. These modifiable risk factors do not influence the diagnosis of OA and RA but may impact the treatment options and recommendations. For example, it may be recommended that someone with OA lose weight or stop long distance running before trying any invasive procedures to see if it resolves symptoms. Because of the increased risk of post-surgical complication, some surgeons refuse to do any surgeries if a patient smokes or has a BMI over 40 (J. Nessler, personal communication, May 2, 2019).
Courtney, P. M., Bohl, D. D., Lau, E. C., Ong, K. L., Jacobs, J. J., & Della Valle, C. J. (2018).
Risk adjustment is necessary in medicare bundled payment models for total hip and knee arthroplasty. The Journal Of Arthroplasty, 33(8), 2368–2375. doi: https://doi-org.ezp.waldenulibrary.org/10.1016/j.arth.2018.02.095
Harvard Medical School. (n.d.). Explain the pain – is it osteoarthritis or rheumatoid arthritis?
Retrieved on June 1, 2019 from https://www.health.harvard.edu/pain/explain-the-pain–is-it-osteoarthritis-or-rheumatoid-arthritis
Huether, S.E., & McCance, K.L. (2017). Understanding pathophysiology (6th ed.). St. Louis,
Rath, L. (n.d.). Knee replacement and revision surgeries on the rise. Retrieved on June 2, 2019 from https://www.arthritis.org/living-with-arthritis/treatments/join surgery/types/knee/knee-replacement-younger-patients.phpNessler, J. (2019, May 2). Personal interview.