Approach to knee pain in the adult

ED: emergency department; ACL: anterior cruciate ligament; PCL: posterior cruciate ligament; MCL: medial collateral ligament; LCL: lateral collateral ligament; RA: rheumatoid arthritis.
* Joint aspiration and fluid analysis are important for diagnosing these conditions.
¶ Includes local joint infection or disseminated infection (eg, gonococcal).
Δ Osteoarthritis can cause diffuse or focal pain in any of several locations.
◊ Symptomatic degenerative meniscal tears may or may not be associated with a small effusion.