A 65-year-old woman comes to the office due to progressively worsening right knee pain. The patient has had the pain for 2 years but never sought medical attention and last saw a physician 5 years ago. The pain, which is worse in the evening, was initially responsive to over-the-counter analgesics, but they gradually lost effectiveness and she stopped taking them. There is no history of trauma to the joint. Medical history is unremarkable. The patient recently retired from her occupation as an elementary school janitor. She does not use tobacco, alcohol, or illicit drugs. Blood pressure is 160/100 mm Hg and pulse is 70/min. BMI is 34 kg/m². Knee examination shows tenderness over the medial tibial condyle and a small joint effusion. Range of motion of the knee elicits bony crepitus. Which of the following is the most likely diagnosis in this patient?

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Explanation: 11ec25c8_d510_60c9_bc81_5b760fa65733_MD0003_00 This patient has typical characteristics of osteoarthritis (OA), including advanced age, obesity, and chronic joint pain that is worse after activity at the end of the day. OA predominantly affects the large weight-bearing joints of the lower extremities (ie, hips, knees), the small peripheral joints in the hands, and the cervical and lumbar spine. OA is due to degeneration of the articular cartilage and is usually an idiopathic phenomenon of aging, although it can also occur due to acute or chronic joint injury and certain systemic diseases (eg, hemochromatosis). Examination findings suggesting OA in the knee include: Periarticular bony hypertrophy and tenderness Limited range of motion with crepitus and pain Small joint effusion without erythema or warmth Varus or valgus angulation Popliteal (Baker) cyst behind the joint X-rays can confirm the diagnosis. Arthrocentesis shows clear fluid with few inflammatory cells and can be helpful in evaluating patients with acute symptoms. Laboratory testing, including inflammatory (eg, erythrocyte sedimentation rate, C-reactive protein) and serologic (eg, rheumatoid factor) markers, is normal. (Choice A) Pes anserinus pain syndrome (anserine bursitis) is characterized by pain and tenderness over the anteromedial tibia, distal to the joint line. The risk is increased in obese patients, but the symptoms typically evolve over weeks to months (not years), and the pain is often worse overnight or in the morning. Because pes anserinus is an extraarticular process, there is no associated crepitus or effusion. (Choice B) Iliotibial band syndrome is a common overuse injury characterized by pain at the lateral knee. Examination shows tenderness at the lateral femoral condyle during flexion and extension. (Choice C) Lateral collateral ligament injuries are uncommon but can occur following a blow to the medial aspect of the knee. Examination would show laxity of the knee with varus stress. (Choice D) Like OA, medial meniscal injuries may display crepitus and a small effusion on examination. However, although older patients may have chronic, degenerative tears, meniscal tears are more common following acute (eg, athletic) twisting injury in younger patients. Also, patients typically experience locking or catching of the knee during extension. (Choice F) Patellofemoral pain syndrome is an overuse disorder commonly seen in young women. It is characterized by diffuse anterior knee pain that is reproduced by patellofemoral compression during knee extension. Educational objective: Osteoarthritis causes chronic joint pain and is most common with advanced age, obesity, and prior joint injury. Examination findings include bony enlargement and tenderness, crepitus with movement, and painful or decreased range of motion. References: Osteoarthritis: diagnosis and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/22230308)

A 65-Year-Old Woman Comes to the Office Due to Progressively