Sports Medicine Research: In the Lab & In the Field: Diagnostic Ultrasound can Shed Light on Knee Health After an Injury (Sports Med Res)

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Wednesday, February 20, 2019

Diagnostic Ultrasound can Shed Light on Knee Health After an Injury

Ultrasonographic Assessment of Femoral Cartilage in Individuals with Anterior Cruciate Ligament Reconstruction: A Case-Control Study

Harkey MS, Blackburn JT, Nissman D, Davis H, Durrington I, Rizk C, Kuismanen A, & Pietrosimone B.  J Athl Train. 2018; 53(11):2081-1088.  DOI: 10.4085/1062-6050-376-17

Take Home Message: Diagnostic ultrasound can detect differences in cartilage thickness in a knee with an anterior cruciate ligament reconstruction compared with the uninjured knee and healthy people.

A patient after an anterior cruciate ligament reconstruction (ACLR) is at elevated risk of osteoarthritis.  Unfortunately, we have no treatment options to slow or reverse osteoarthritis progression. Therefore, our best option is to prevent osteoarthritis; but, to prevent osteoarthritis a clinician needs to have ways to detect who will likely develop osteoarthritis after an ACLR.  Diagnostic ultrasound is a clinically accessible method for sports medicine professionals to achieve this goal by observing changes in structures like articular cartilage. The researchers of this study used diagnostic ultrasound to compare anterior femoral cartilage thickness between knees of people with a history of ACLR and between knees with an ACLR or healthy controls. They recruited 20 people with unilateral ACLR that were greater than 6 months post-surgery and 28 healthy individuals with similar demographics from the same population.  The authors specifically assessed cartilage thickness at the medial, lateral, and intercondylar areas. ACLR participants had thicker medial condyle cartilage and greater cartilage cross-sectional area in their ACLR knee compared to their uninjured knee and compared to healthy individuals. The researchers used a limb symmetry index (involved/uninvolved x 100) to provide a quantitative comparison of cartilage measurements between limbs within the ACLR participants. Using this measure, the researchers found that patients with more cartilage surface area in the involved knee seemed to be further away from their ACLR surgery date. 

These findings are interesting because they show relative early cartilage differences 1 to 5 years post ACLR in the involved limb compared to their uninjured limb and healthy controls.  It would be interesting to continue to follow these participants to gain a better understanding of the speed of cartilage changes over time in comparison to their uninjured limb or to healthy controls.  The authors have shown that ultrasound may provide an early opportunity to monitor progressive changes and tolerance to physical activity.  Interestingly, cartilage thickening is thought to be a very early stage of OA despite the cause being unknown.  Thickening may be related to cartilage swelling, which weakens the tissue. In this scenario, loading activities can exacerbate further degradation.  This may be an opportunity to intervene prior to osteoarthritis by better managing the loading environment.  However, it’s important to acknowledge that these changes may also be a positive adaption as the knee tries to adapt and protect itself from new loading patterns. Future research is needed to see how these changes on ultrasound relate to the risk of osteoarthritis. Cartilage changes may serve as an easily assessed marker for underlying biomechanical and biochemical changes within the knee. Asymmetrical or unexpected changes may ultimately leave a patient more susceptible to the repetitive wear of daily and physical activities.  It would have been interesting to see if gait kinematics were associated with these cartilage changes, as well as how these patients’ knee or general health symptoms related to cartilage presentation.  This study is a nice demonstration that ultrasound may serve as a potential tool for clinicians to identify and monitor cartilage changes in patients during their rehabilitation and return to physical activity so that they can most safely return with limited long-term complications.      

Questions for Discussion:  Are you aware of any ultrasound measurements occurring within your clinical practice? How do you think access to ultrasound measures could impact your clinical practice?

Written by: Nicole Cattano
Reviewed by: Stephen Thomas

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