A 29-year-old woman comes to the office for evaluation of knee pain. For the last 3 months, the patient has had pain around the anterior aspect of the left knee. She has been taking ibuprofen, which initially improved the symptoms but now does not despite multiple doses throughout the day. The pain is worse when the patient walks up or down stairs, and she has to rest when walking up to her third-floor apartment. She has no chronic medical conditions and has had no previous surgeries. The patient smokes half a pack of cigarettes a day and drinks socially on weekends. Temperature is 36.7 C (98 F), blood pressure is 110/60 mm Hg, and pulse is 68/min. BMI is 26 kg/m². Inspection of the left leg shows mild quadriceps atrophy with no visible bony deformity. There is no pain with palpation over the patellar tendon and no evidence of swelling. Which of the following additional examination findings is most likely to be seen in this patient?

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11ec25c8_d2c2_040a_bc81_9332b8825002_MD0003_00 This patient has patellofemoral pain syndrome (PFPS), a common cause of chronic, poorly localized anterior knee pain in young women. The etiology is variable; contributing factors include overuse, malalignment, and acute injury to the knee, but by convention, the pain is not due to intraarticular (eg, meniscus) or peripatellar (eg, patellar tendon/ligament) disorders. The diagnosis of PFPS is based on clinical findings, although no individual feature has high predictive value. Running, negotiating stairs, and prolonged sitting often aggravate the pain. Atrophy or weakness of the quadriceps or hip abductors is common, and rotational or varus/valgus malalignment may be noted. Provocation of pain during tonic contraction of the quadriceps with the knee flexed (eg, squatting, lunging) strongly suggests the diagnosis. Imaging (eg, x-ray, MRI) is usually normal and needed only to exclude other disorders. Management includes strengthening exercises for the quadriceps and hip abductors; a short course of nonsteroidal anti-inflammatory drugs can also help. (Choice A) Anterior laxity of the tibia (eg, anterior drawer, Lachman tests) indicates an anterior cruciate ligament (ACL) tear, which typically presents with acute pain and hemarthrosis after a blow to the knee or twisting injury. anterior drawer, Lachman tests (Choice B) Discomfort, as indicated by an apprehensive expression on the patient's face, during lateral displacement of the patella suggests patellar instability, which is only an occasional finding in PFPS. (Choice C) Erythema and swelling at the joint line are usually acute findings and suggest hemarthrosis (eg, ACL tear), acute meniscal tear, or inflammatory arthritis (eg, gout). They are atypical in PFPS. (Choice D) Loss of knee extension suggests disruption of the extensor mechanism from a tear of the patellar or quadriceps tendon. These injuries typically occur in major trauma and are associated with swelling and deformity. (Choice F) Tenderness at the tibial tubercle suggests Osgood-Schlatter disease, which is caused by repetitive strain at the insertion of the patellar tendon. This disorder occurs in preadolescent and adolescent patients during rapid growth spurts and is uncommon in adults. Osgood-Schlatter disease Educational objective: Patellofemoral pain syndrome is a common cause of chronic anterior knee pain in women. Diagnosis is based on clinical findings; symptoms are typically reproducible with isometric quadriceps contraction (eg, squatting). Treatment includes strengthening the quadriceps and hip abductors. References: Patellofemoral pain syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/20610028)

A 29-Year-Old Woman Comes to the Office for Evaluation of Knee