Horizontal fissuring at the osteochondral interface: a novel and unique pathological feature in patients with obesity-related osteoarthritis

Abstract

ObjectivesObesity is a well-recognised risk factor for osteoarthritis (OA). Our aim is to characterise body mass index (BMI)-associated pathological changes in the osteochondral unit and determine if obesity is the major causal antecedent of early joint replacement in patients with OA.MethodsWe analysed the correlation between BMI and the age at which patients undergo total knee replacement (TKR) in 41 023 patients from the Australian Orthopaedic Association National Joint Replacement Registry. We then investigated the effect of BMI on pathological changes of the tibia plateau of knee joint in a representative subset of the registry.Results57.58% of patients in Australia who had TKR were obese. Patients with overweight, obese class I & II or obese class III received a TKR 1.89, 4.48 and 8.08 years earlier than patients with normal weight, respectively. Microscopic examination revealed that horizontal fissuring at the osteochondral interface was the major pathological feature of obesity-related OA. The frequency of horizontal fissure was strongly associated with increased BMI in the predominant compartment. An increase in one unit of BMI (1 kg/m2) increased the odds of horizontal fissures by 14.7%. 84.4% of the horizontal fissures were attributable to obesity. Reduced cartilage degradation and alteration of subchondral bone microstructure were also associated with increased BMI.ConclusionsThe key pathological feature in OA patients with obesity is horizontal fissuring at the osteochondral unit interface. Obesity is strongly associated with a younger age of first TKR, which may be a result of horizontal fissures.

Pathogenesis and clinical management of obesity-related knee osteoarthritis: Impact of mechanical loading

“…[ 14 ] Less cartilage degradation from superficial zone Chen et al. [ 10 ] Osteochondral interface Increased incidence of horizontal fissuring Increased length, increased area of fissuring Chen et al. [ 10 ] Subchondral bone Increased bone volume fraction, more plate-like trabecular bone, increased trabecular space, increased trabecular number Reina et al.…”

“…[ 16 ] Increased osteoid formation, decreased bone mineral density and bone volume Chen et al. [ 10 ] Osteophyte Higher incidence of knee osteophytes Hart et al. [ 17 ] Synovium Marked fibrosis Increased macrophage infiltration Higher level of Toll-like receptor 4 expression, higher level of adiponectin and adipose-related markers peroxisome proliferator-activated receptor γ (PPARγ) Increased hematopoietic cells, M2-type macrophages Harasymowicz et al.…”

“…The novel pathological findings of horizontal fissuring, characterized by irregular erosion, free bone/cartilage debris, fibro-granulation tissue and the rupture of microcapillaries at the osteochondral interface, is the key pathological feature in patients with obesity-related OA. The unique feature of horizontal fissuring in obese patients with OA suggested that mechanical factors play a key role in the pathogenesis of obesity-related OA [ 10 ].…”

“…Our recent study showed that BMI was positively associated with increased osteoid formation, but negatively associated with total bone volume and bone mineral density in the predominant compartment of knee OA [ 10 ]. While low bone volume and mineral density may be due to the high prevalence of vitamin D insufficiency or deficiency in the obese individual [ 34 ], Reina et al.…”

“…A study that examined the effect of mechanical stress and obesity-related systemic factors on knee and hand OA showed that obesity-related mechanical stress was the most important risk factor for knee OA [ 7 , 8 ]. Causation can be difficult to prove in a noninfectious disease, however, there is increasing evidence showing that OA is a disease primarily of mechanics, whereas the inflammation in OA is more so a secondary consequence of this [ 9 , 10 ]. In this review, we focused on discussing the effect of obesity-related biomechanical factors on OA development, and the management of obesity-related OA based on adjusting the abnormal biomechanics.…”