Cartilage and bone markers and inflammatory cytokines are
increased in synovial fluid in the acute phase of knee injury (hemarthrosis) –
a cross sectional analysis

P, Frobell R, Englund M, Roos H & Struglics A. Osteoarthritis and
2012, 20: 1302-1308. 

knee injuries, including anterior cruciate ligament (ACL) tears, are known to
increase an athlete’s risk of developing osteoarthritis (OA).  Rate of OA incidence seems to be at an
increased risk, despite whether an athlete gets ACL surgery or not.  There are various biomechanical as well as
biochemical theories as to why this may be. One biochemical theory being that
the acute inflammatory process that follows a knee injury propagates OA.  Therefore the purpose of this study was to
investigate the biochemical markers within 1 month of an acute knee injury (i.e.
any rotational injury with hemarthrosis) and compare them to healthy knees, as
well as to see if time from injury affects concentrations.   Synovial fluid (SF) was aspirated once and
analyzed in 111 acutely injured knees at varying time points within the 1 month
window post-injury based on when the injured knee was seen.  SF concentrations of specific markers for
cartilage (i.e., aggregan), bone (i.e., osteopontin, osteonectin), and all
pro-inflammatory cytokines (signalling proteins; i.e., IL-1β, IL-6, IL-8, and
TNF-α) were significantly higher at all time points when compared to the
healthy controls.  This study also found
a time-dependent response of certain cartilage markers being higher in the days
immediately following knee injury. 
Markers remained elevated when compared to healthy controls, but started
to become lower the longer it was from the time of injury.

early inflammatory response in acutely injured knees may start a cascade of
events that lead to irreversible changes to the entire joint environment.  Clinically it is important to take this into
consideration for future research as well as when applying rehabilitation
techniques, recommending interventions, or modifying activities of daily
living.  While this study finds some
interesting elevations of biomarkers, the question still remains “what can we
do clinically about this.”  Unfortunately
I think it is still too early to tell. 
There is not enough evidence to stop doing rehabilitation in days immediately
following injury or to make treatment modifications due to these elevated
markers, but clearly these biomarkers are an issue that warrants more
attention.  Within 1 month of an acute
knee injury, there may be no evidence of structural changes, but this provides
a unique window of opportunity to intervene and help a patient maintain a
better long-term quality of life. 
Biochemically the knee is altered and this may be the lone condition
needed to start the development of OA.  Other
studies have found that some markers remain elevated as much as 1 year
post-injury (Beynnon et
).  Is there anything that we may
be able to do as clinicians to help these athletes?  Are there things that we can implement to
help return these biochemical levels to normal?

by: Nicole Cattano
by: Stephen Thomas

Related Posted

Swärd P, Frobell R, Englund M, Roos H, & Struglics A (2012). Cartilage and bone markers and inflammatory cytokines are increased in synovial fluid in the acute phase of knee injury (hemarthrosis) – a cross-sectional analysis. Osteoarthritis and Cartilage, 20 (11), 1302-8 PMID: 22874525