Research Shows Biological Responses Associated with Outcome of 2-Year Knee Injuries

July 1, 2021
Armand Butera

Armand Butera is the assistant editor for HCPLive. He attended Fairleigh Dickinson University and graduated with a degree in communications with a concentration in journalism. Prior to graduating, Armand worked as the editor-in-chief of his college newspaper and a radio host for WFDU. He went on to work as a copywriter, freelancer, and human resources assistant before joining HCPLive. In his spare time, he enjoys reading, writing, traveling with his companion and spinning vinyl records. Email him at

The investigators linked immediate biological responses and symptomatic and structural outcomes to long-term injuries in active patients.

Researchers from London investigated whether predefined baseline demographics and clinical factors, as well as protein analytes in knee synovial fluid and in plasma or serum, were associated with relevant outcomes at 2 years after knee injury.

The study found that the biggest factors associated with adverse outcomes at 2 years after knee injury were blood in the knee joint, effusion, and joint injury inflammatory responses measured in synovial fluid.

The longitudinal study drew data from 6 hospitals and clinics in the London area from November 1, 2010-November 28, 2014.

The study, led by Cesar Garriga, PhD, referenced the immediate biological responses to acute knee injury, which was often typified by a variable inflammatory response. The investigators also noted that the magnitude of inflammation in patients is typically associated with early clinical outcomes in the months after knee injury.

Garriga and colleagues hypothesized that the immediate biological response to acute joint injury would be associated with the outcomes recorded 2 years after the injury.


The longitudinal cohort study followed 150 participants with an age range of 16-50 years old.

Before injury, 114 of the participants were sports professionals, and the remaining participants engaged in sports activities. Half of all participants had medium-to-large clinical effusions at their baseline assessment, and additional concerns of hemarthrosis and synovial fluid were recorded as well.

Nearly all the participants (n = 145) underwent knee surgery that included a washout at a median of 17 days after injury.

Participants were asked to participate in a screening by an orthopedic surgeon investigator (AW), as well as complete a self-reported questionnaire that would generate results for the Knee Injury and Osteoarthritis Outcome Score (KOOS4) and Tegner activity scores.

Finally, extended knee x-rays were taken at baseline and 2 years, as well as MRI scans. Biological samples were taken at baseline, 14 days, 3 months, and while participants attended study visits at 2 and 5 years.


The research showed that 22 (15%) of 150 participants had new tibiofemoral radiographic osteoarthritis at 2 years. Meniscal tears uncovered by MRI scans were linked to the condition.

Additionally, the study found that the biggest factors associated with adverse outcomes at 2 years after knee injury were blood in the knee joint, effusion and joint injury inflammatory responses measured in synovial fluid.

“The combination of effusion and hemarthrosis was significantly associated with symptomatic outcomes after acute knee injury,” the investigators wrote. “The synovial fluid molecular protein response to acute knee injury was independently associated with symptomatic outcomes but not with structural outcomes, with the biomarkers overall playing a minor role relative to clinical predictors. The relationship between symptoms and structure after acute knee injury and their apparent dissociation early in this process need to be better understood to make clinical progress.”

The study, “Clinical and molecular associations with outcomes at 2 years after acute knee injury: a longitudinal study in the Knee Injury Cohort at the Kennedy (KICK)”, was published online in The Lancet Rheumatology.