Post-Traumatic Osteoarthritis Following ACL Injury

Li-Juan Wang; Ni Zeng; Zhi-Peng Yan; Jie-Ting Li; Guo-Xin Ni


Arthritis Res Ther. 2020;22(57) 

In This Article

Early Detection of PTOA

PTOA is a progressive pathogenetic process, and it could be too late to intervene when it progresses to a late stage. Therefore, there is a compelling need to improve diagnostic techniques in order to detect PTOA at an early stage. Currently, imaging modalities such as bone scans, radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) and specific biomarkers (biospecimen: blood, serum, synovial fluid, and other tissue samples)[3,17–19] allow early detection.

Radiography is a commonly used technique to diagnose OA. However, current clinical criteria such as the Kellgren–Lawrence and Outerbridge classification schemes are not sensitive enough to detect early changes of OA, and there is interobserver disagreement when classifying patients.[17] Additionally, radiography is a two-dimensional imaging modality and has limited ability to provide information on ligaments, the synovium, the meniscus, and the articular cartilage.[17,20]

As a repeatable, non-invasive, and multi-planar imaging modality, MRI has been widely used to longitudinally evaluate joint tissues following traumatic injuries.[20] It can perform more sophisticated analysis of various structures within the joint and even quantify the severity of the injury, for instance, characterizing metabolic-triggered subchondral bone damage, evaluating bone marrow lesions, detecting biochemical changes in the cartilage matrix and early cartilage matrix loss, and analyzing cartilage matrix composition.[3,20–22] T1rho is a technique used to assess proteoglycan content of the extracellular matrix of articular cartilage. And T2 mapping has been used to detect the structural integrity, organization, and water content of cartilage.[20] Physiological MRI has also been used to detect early changes during OA development. Na18F positron emission tomography with computed tomography (PET/CT) co-registered with MRI has been demonstrated to be a sensitive imaging modality in an in vivo canine model to detect molecular and cellular changes in bone metabolism before morphological signs appear.[4] The lower delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) index has been shown to have prognostic value for OA development after ACL injury.[23] However, MRI scans are expensive and not available everywhere.[17]

A variety of molecular and biochemical processes play important roles in the pathogenesis of PTOA. The detection of molecules in the acute phase provides indications of the future disease process. Breakdown of ECM structures including type II collagen, proteoglycans (PGs), and glycosaminoglycans (GAGs) may be one of the earliest signs of OA and could be detected before radiographic evidence. Elevated concentrations of degradative enzymes for instance matrix metalloprotease (MMP)-1 and MMP-3 in synovial fluid are also measurable after ACL injury. Increased ratio between MMPs and tissue inhibitor of metalloproteinase indicates an increase in degradation relative to synthesis.[24] Given that the alteration of synoviocytes and adjacent chondrocytes may decrease the level of lubricin, the latter is promising as a biomarker of cartilage degradation.[3]