As I noted in an earlier post on acute knee injuries, the University of Michigan Health System Guidelines for Clinical Care “Knee Pain or Swelling: Acute or Chronic” recommends aspiration of an acute knee effusion to decide whether or not the effusion has blood in it(an acute hemarthrosis) or non-bloody. The guidelines recommend that a bloody effusion immediately be referred to a specialist.
Often, specialty evaluation leads to an MRI of knee or less commonly a knee arthoscopy. The purpose of either of these two tests is to determine if there internal soft tissue of the knee. X-rays of knee will detect fractures but not internal soft tissue damage.
The assumption for this diagnostic strategy is that there is less long term damage to the knee if knee surgery is done early after a soft tissue injury. Also it is assumed that draining a hemarthrosis will lessen the patient’s pain.
In the chapter “Initial Management of the Sports Injured Knee”*, the authors consider five questions regarding acute knee injury:
1. “What is the relative frequency of various injuries when patients present with a knee hemarthrosis?”
2. “What is the effectiveness of physical examination in diagnosing an ACL rupture in an acutely injured knee?”
3. “What is the role of MRI vs. arthroscopy in the diagnosis of acute knee injury?”
4. “What is the role for aspiration in the acutely injured knee with hemarthrosis?”
5. “Is there evidence in favor of surgical reconstruction of an acute (<3 weeks) ACL injury?”
For the first question, “What is the relative frequency of various injuries when patients present with a knee hemarthrosis?”, the search strategy was as follows:
They queried the Cochrane database with the search term “knee injury”. They queried PubMed clinical queries search/systemic reviews with the search term “knee injury” AND “hemarthrosis”. They performed a PubMed sensitivity search using key words “knee injury AND hemarthrosis and arthroscopy OR MRI”. The exclusion search terms were “<16 years old, atruamatic injury, road traffic accidents”.
Using the above search strategy they found 13 prospective studies using arthroscopy or MRI and one retrospective study.
They pooled 12 of the studies and found that 57.5% had anterior cruciate injuries, 3.75% posterior cruciate injury, 32.5% meniscus injury, 13% osteocondral damage, and 18.8% had medial collateral injury.
They were unable to state what percentage of hemarthrosis were due to patellar dislocation because most of the studies did not report that. However, they cited a review in which patellar dislocation was said to be diagnosed in 4 to 23% of cases with hemarthrosis.
Their search strategies for the other four questions are detailed in in the book inChapter 93, pp 796-802*.
For question two, they state that Lachman test is most sensitive test for an acute ACL rupture and the pivot shift test is the most specific.
For question three, they conclude based on their search results, that early MRI rather than arthroscopy should be the next test if the physical examination is equivocal.
For question four, they conclude that there is no evidence for or against aspiration “for symptomatic relief or functional improvement in the acutely injured knee with hemarthrosis.”
And finally the fifth question is, “Is there evidence in favor of surgical reconstruction of an acute (<3 weeks) ACL injury?”
Their literature search on the fifth question leads them to conclude that “There is no difference in surgeon and patient-based outcomes when comparing early and delayed ACL reconstruction. Early structured rehabilitation and delayed optional reconstruction for the symptomatic patient is recommended for the acutely injured patient as opposed to routine early reconstruction.”
*Evidence-Based Orthopedics, First Edition. Edited by Mohit Bhandari.
© 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd.