PubMed abstract / permitted excerpt

Knee pain is common, with more than 30% to 45% of middle-aged and older adults having symptomatic osteoarthritis, and 25% to 40% of younger adults having patellofemoral pain syndrome. Components of a detailed history include time of onset; pain duration, quality, and localization; trauma/mechanism of injury; swelling; popping/clicking; aggravating and alleviating factors; sports activities; and limitations to current activity. The physical examination for evaluating knee pain involves five overall components: inspecting the joint for obvious abnormalities, palpating the joint to identify effusion or points of tenderness that may be the source of the pain; testing active and passive range of motion; testing strength; and performing specialized maneuvers that evaluate specific knee joint structures. These maneuvers are most accurate when performed in combination, rather than relying on one specific maneuver to make the diagnosis. In addition to these five examination components, imaging should be obtained if appropriate, with plain radiography typically being the first step. With traumatic injuries, clinical decision rules such as the Ottawa Knee Rule can determine if radiography is needed to detect fractures or other injuries that may require referral. Additional evaluations can include arthrocentesis when joint effusion is present, optimally guided by point-of-care ultrasonography when available, and laboratory testing if infection or inflammatory disorders are suspected.