Frequently Asked Questions

Knee Swelling Questions

Q. My knee swelled up considerably after a ski injury.  Should I be worried?

A.Swelling within the knee can occur either from increased joint fluid formation or bleeding within the joint.  Usually if there is increased joint fluid production it is suggestive that there is a mechanical problem within the joint.  Examples could be a torn cartilage (meniscus), a loose body (bone chip), arthritis.  If bleeding occurs within the joint it is suggestive of a more significant injury.  Following trauma the most common cause of acute bleeding (hemarthrosis) is a 1) torn anterior cruciate ligament.  Other causes of a hemarthrosis include 2) a fracture within the joint, 3) peripheral tears of the meniscus (the peripheral one third has a blood supply), 4) a tear of the posterior cruciate ligament (PCL), or 5) dislocation of the patella (kneecap).  There are also less common causes of bleeding within the joint but these are the ones we think of as orthopaedic surgeons.  In this situation if the swelling occurred within a 3 hr time period following the injury we would be most concerned about a torn ACL.  Sometimes your surgeon will recommend removing the fluid by inserting a needle into the joint.  This is called a joint aspiration.  If a patient has recurrent swelling seemingly unrelated to trauma a joint aspiration may be recommended to remove fluid and have it analyzed in the lab.  Diagnoses like gout, pseudogout, and rheumatologic conditions may be diagnosed by a joint fluid analysis. 


Q. My knee is really swollen and hurts a lot. Will an aspiration help?

A. Yes!  If your knee is swollen removal of the fluid will reduce the tension on the joint capsule and you should feel more comfortable and have improved knee motion. Sometimes following surgery we may perform a knee aspiration.  If a patient has severe pain associated with knee swelling after surgery we may aspirate the knee to make certain that an early knee joint infection is not beginning to develop.  In this situation we will inspect the joint fluid and send it off to the lab.  They will perform a synovial fluid analysis and will also culture the fluid to determine if bacteria grows out from the fluid.