A 52-year-old woman comes to the office due to pain in the right knee for the past several months. The pain is typically better in the morning but worsens by the end of the day. There is no history of trauma to the joint. Medical history is significant for hypertension, type 2 diabetes mellitus, and hypercholesterolemia. The patient is a lifetime nonsmoker. She works as an office clerk. Family history is significant for stroke in her mother and gout in her father. Temperature is 37.2 C (99 F), blood pressure is 145/95 mm Hg, and pulse is 90/min. BMI is 37 kg/m². Physical examination shows crepitation on flexion and extension of the right knee; range of motion is otherwise normal, and there is no swelling, warmth, or redness. Which of the following pathologic processes is most likely occurring in this patient's knee joint?

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11ec160b_3a5f_05e9_9249_3195f0f30a54_MD0001_00 This patient has chronic knee pain associated with crepitus, which is consistent with osteoarthritis (the most common form of arthritis). Besides the knees, osteoarthritis also commonly affects the hips, lumbar spine, and distal joints of the hands. Patients typically have pain that worsens with activity and is relieved by rest. Osteoarthritis typically progresses with age and is accelerated in patients with prior joint injury or excessive mechanical stresses (eg, obesity, joint deformities). Osteoarthritis is characterized by progressive fissuring, flaking, and erosion (fibrillation) of articular cartilage. The etiology is multifactorial, with excessive biomechanical stress and increased intraarticular metalloproteinase activity as the major contributors to cartilage destruction. Although a number of proinflammatory mediators (eg, IL-6, macrophage chemotactic protein-1) have been linked to osteoarthritis, overt signs of synovitis (eg, redness, warmth) are less prominent than in the classic inflammatory arthritic disorders (eg, gout). Effusions, if present, are often small. (Choice A) Calcium pyrophosphate deposition disease presents with an acute inflammatory arthritis resembling gout (ie, pseudogout). Although this disorder is common in the knee, chronic arthritis without signs of acute synovitis is more consistent with osteoarthritis. (Choice C) Hemochromatosis can cause deposition of iron salts within the synovium and joint space, which can lead to a chronic arthritis resembling osteoarthritis. Although hereditary hemochromatosis is associated with diabetes mellitus, this patient lacks other characteristic findings (eg, skin pigmentation, liver dysfunction, cardiac enlargement); in addition, osteoarthritis is a much more common cause of arthritis in the general population. (Choice D) Rheumatoid arthritis is an inflammatory arthritis associated with synovial hyperplasia. It most commonly affects the proximal interphalangeal (PIP), metacarpophalangeal (MCP), wrist, knee, and ankle joints. However, patients typically have symmetric joint involvement and prolonged morning stiffness. (Choice E) Parvovirus B19 presents in adults as a nonspecific flulike illness, often followed by a symmetric arthritis most commonly affecting the hands. Symptoms are acute and resolve within a few weeks. Educational objective: Osteoarthritis is characterized by progressive fissuring and erosion of articular cartilage. Risk factors include advancing age, obesity, joint trauma, and repetitive stress. Patients may have mild effusion and crepitus on physical examination, but signs of synovitis (eg, redness, warmth) are less prominent than in the classic inflammatory arthritic disorders. __________ References: Osteoarthritis. (http://www.ncbi.nlm.nih.gov/pubmed/27734845)

A 52-Year-Old Woman Comes to the Office Due to Pain