CASE A 73-year-old woman presents to your clinic with 1 year of gradual-onset left knee pain. The pain is worse at the medial knee and at the beginning and end of the day, with some mild improvement after activity in the morning. The patient has already tried oral acetaminophen, an over-the-counter menthol cream, and a soft elastic knee brace, but these interventions have helped only minimally.
On physical exam, there is no obvious deformity of the knee. There is a bit of small joint effusion without redness or warmth. There is mild tenderness to palpation of the medial joint line. Radiographic findings include osteophytes of the medial and lateral tibial plateaus and medial and lateral femoral condyles with mild joint-space narrowing of the medial compartment, consistent with mild osteoarthritis.
How would you manage this patient’s care?
The knee is the most common joint to be affected by osteoarthritis (OA) and accounts for the majority of the disease’s total burden.1 More than 19% of American adults ages ≥ 45 years have knee OA,1,2 and more than half of the people with symptomatic knee OA in the United States are younger than 65 years of age.3 Longer lifespan and increasing rates of obesity are thought to be driving the increasing prevalence of knee OA, although this remains debated.1 Risk factors for knee OA are outlined in TABLE.1,4-8
Diagnosis: Radiographs are helpful, not essential
The diagnosis of knee OA is relatively straightforward. Gradual onset of knee joint pain is present most days, with pain worse after activity and better with rest. Patients are usually middle-aged or older and/or have a distant history of knee joint injury. Other signs, symptoms, and physical exam findings associated with knee OA include: morning stiffness < 30 minutes, crepitus, instability, range-of-motion deficit, varus or valgus deformity, bony exostosis, joint-line tenderness, joint swelling/effusion, and the absence of erythema/warmth.1,9,10
Although radiographs are not necessary to diagnose knee OA, they can be helpful in confirming the diagnosis by assessing the degree and location of OA and ruling out other pathology. Standing, weight-bearing radiographs are particularly helpful for assessing the degree of joint-space narrowing. In addition to joint-space narrowing, radiographic findings indicative of knee OA include marginal osteophytes, subchondral sclerosis, and subchondral cysts. (See FIGURE 1.)
Keep in mind that radiographs are less sensitive for early OA, that the degree of OA seen on radiographs does not correlate well with symptoms, and that radiographic evidence of OA is a common incidental finding—especially in elderly individuals.11 Although not routinely utilized for knee OA diagnosis, magnetic resonance imaging (MRI) can be used to assess for earlier stages of the disease and to rule out pathology associated with the soft tissue and cartilage that is not directly associated with OA.
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