ABIM Exam Disease of the Week Profile: Osteoarthritis
Osteoarthritis is a common condition and is a topic every internist should have a firm grasp of – in practice and for the Internal Medicine Board (ABIM) Exam.
Due to the aging baby boomer population and the increase in abdominal girth throughout the US and other parts of the world, any condition in the 21st century whose main risk factors include increased age and obesity can expect to increase in prevalence and prominence. Such is the case with the featured disease of the week: osteoarthritis.
PATHOPHYSIOLOGY AND CLINICAL FEATURES
Osteoarthritis is a chronic, non-inflammatory, non-systemic condition that has mono-articular (single joint) or oligo-articular (few joints) involvement. In simple terms, this condition does not occur overnight and progresses over several years. Non-inflammatory simply means that the joint will usually not get red or warm. If morning stiffness does occur, it will usually last for less than thirty minutes. However, swelling can occur from osteoarthritis. It is a non-systemic condition, as the joint gets affected without interrupting the integrity of the entire body. This phenomenon differs from another arthritic condition: rheumatoid arthritis.
Rheumatoid arthritis is an autoimmune disease that involves a specific antibody (anti-CCP) that can disseminate the bloodstream to affect different organs of the body. Osteoarthritis traditionally occurs because of “wear and tear” of a joint over several years. It is an active disease process that destroys the chemical composition and structural integrity of cartilage. Cartilage surrounds bone and minimizes friction between bones moving against each other. With deterioration of cartilage, bones make contact with one other, which causes “bone on bone” phenomenon to occur and, thus, the pain associated with osteoarthritis.
Osteoarthritis most commonly affects the weight bearing joints of the body, such as the hips or knees. Other joints that can be affected are the back, PIP (Bouchard’s node) and DIP joint (Heberden node). Initially patients will complain of joint pain that worsens with activity and improves with rest. Since it is a chronic, progressive, and debilitating condition, the pain continues to worsen over several years and limit mobility. Patients with osteoarthritis of the knee may have a crackling sound that can be appreciated with flexion of the joint—known as crepitus.
Risk factors for developing osteoarthritis include obesity, advanced age, repetitive use of a joint, history of trauma, diabetes mellitus, hyperparathyroidism, and chondrocalcinosis (calcification of the cartilage).
Diagnosis of osteoarthritis is primarily done clinically. Obtaining imaging like an x ray or MRI will only help enhance your clinical suspicion of the diagnosis. With osteoarthritis, osteophyte formation, periarticular osteopenia, joint space narrowing, or subchondral sclerosis can be visualized as common radiographic findings. When swelling does occur and an arthrocentesis (joint tap) is required, the white blood cells are in the range of 200-2000/uL, within the non-inflammatory range. Therefore, inflammatory markers like ESR and C-reactive protein tend to remain in the normal range.
Management of osteoarthritis is broken down into non-pharmacological intervention, pharmacological intervention, intra-articular intervention, and surgical intervention. Non-pharmacological intervention includes weight reduction and weight resistance training. Weight reduction is particularly important in individuals who have osteoarthritis of the hip or knee as weight reduction slows progression of osteoarthritis and provides symptomatic relief since there isn’t as much pressure being applied to the specific joint. Using a cane or walker can also be warranted in individuals with osteoarthritis of the hip or knee. If an individual uses a cane for osteoarthritis, he or she should be instructed to use the cane in the contralateral (opposite) hand of the affected hip or knee joint to relieve symptoms.
Pharmacological intervention starts with using NSAIDs or acetaminophen for symptomatic relief. NSAIDS must be taken with food and/or given with proton pump inhibitors as excessive use of NSAIDS can cause the formation of gastric ulcers or peptic ulcer disease. If NSAIDs or acetaminophen don’t provide symptomatic relief, then stronger analgesics are recommended such as tramadol, which is a non-opioid analgesic. This medication does not cause constipation or sedation but should be avoided in patients who are taking SSRIs (selective serotonin reuptake inhibitors) for depression or other psychiatric conditions as the combination can cause either seizures to develop or serotonin syndrome. Narcotics, such as hydrocodone and propoxyphene, may be appropriate for some patients with osteoarthritis, especially those individuals who are not candidates for surgical therapy. However, whenever possible, narcotics should be given short term to prevent tolerance or dependence from occurring. Narcotics also have an unfavorable side effect profile. Two of the most common side effects of narcotic use are constipation and nausea and vomiting.
Intra-articular injections with corticosteroids can provide rapid but temporary relief of hip and knee osteoarthritis. Relief is patient dependent but most patients have relief for up to three months. It is, therefore, not recommended to give steroid injections before three months. Giving steroid injections can increase chance of infections of a joint if given repeatedly. It is contraindicated in individuals who have inflammatory features (redness, warmth, and persistent stiffness) as this can indicate that patient may have septic arthritis. Therefore, septic arthritis must be ruled out first by performing an arthrocentesis as performing an intra-articular steroid injection to a septic arthritic joint can exacerbate the septic arthritis.
Surgical intervention (arthroplasty-joint replacement) of hip or knee joint is performed by an orthopedic surgeon and is reserved for individuals who have exhausted both non-pharmacological and pharmacological interventions and still continue to have debilitating symptoms. Although clinical symptoms have precedence over radiographic findings for whether surgical intervention should be entertained, radiographic changes are usually severe by the time arthroplasty is considered. Individuals who undergo joint arthroplasty and live beyond ten years after the procedure should be cautioned that prosthetic implants may eventually loosen and require surgical replacement. If recurrent prosthetic infections occur, the prosthesis needs to be removed and prolonged antibiotic therapy may be required.
You can see all the previous ABIM Exam disease of the week blog posts at the Knowmedge Blog. You can find also additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.