Intra-Articular Mineralization May Have Pathogenic Effects on Knee Osteoarthritis

Intra-articular (IA) mineralization may have a pathogenic effect on the structural progression of knee osteoarthritis (OA), according to study results published in Arthritis & Rheumatology.

Using data from the longitudinal Multicenter Osteoarthritis (MOST) study, researchers investigated the relationship between IA mineralization and cartilage worsening over 2 years among older patients with or at risk for OA.

Included patients came from 2 cohorts in the MOST study:

• The original cohort, which comprised patients aged from 50 to 79 years at risk for OA
• The new cohort — recruited at the 12-year study visit  — which comprised patients aged from 45 to 69 years with a Kellgren/Lawrence (KL) grade of 2 or less for both knees, with no or only mild knee pain

The 12-year study visit was considered baseline for the current analysis. Computed tomography (CT) exams were conducted at the 12-year visit to detect the presence of IA mineralization. Magnetic resonance images (MRIs) of the knee were taken at each study visit to assess cartilage damage.

Intra-articular mineralization was defined as a Boston University Calcium Knee Score greater than 0, while an increase in the MRI OA Knee Score was indicative of worsening cartilage.

A total of 1673 participants with a mean age of 60.1 years were included in the study. Among these, 56% were women, 81% were White, and the mean body mass index was 28.6 kg/m²; 57% of knees were classified as KL grade 0, 26% were grade 1, 13% were grade 2, and 4.6% were grade 3 or 4.

Additionally, 9.0% of all knees were determined to have IA mineralization, which was present in the cartilage (6.3%), meniscus (7.1%), joint capsule (4.0%), and ligaments (3.4%). After 2 years, 47.4% of participants showed cartilage worsening.

Mineralization in any knee tissue was not linked to cartilage worsening anywhere in the knee, with relative risks (RRs) between 1.09 and 1.27. However, cartilage mineralization was tied to a 1.39-fold (95% CI, 1.04-1.88) increased risk for damage in the same knee compartment (medial or lateral tibiofemoral).

Meniscal mineralization was not correlated with cartilage damage at the compartment level (RR, 1.05; 95% CI, 0.79-1.39). For specific subregions, cartilage mineralization raised the risk for cartilage worsening by 1.56 times (95% CI, 1.13-2.17), but meniscal mineralization was not associated with cartilage worsening in adjacent subregions (RR, 1.02; 95% CI, 0.73-1.42).

Sensitivity analyses were conducted according to baseline radiographic OA status. No statistically significant associations were found for knee-level, compartment-specific, or subregion-specific analyses. However, in knees without radiographic OA, the effect sizes were similar to the main results. This was especially evident in subregion-specific analyses of cartilage mineralization, with an RR of 1.74 (95% CI, 0.99-3.07).

When examining MRI subregions with no baseline cartilage damage, cartilage mineralization was linked to a higher risk for new cartilage worsening in the same subregion (RR, 2.76; 95% CI, 1.50-5.08), but no association was found with meniscal mineralization (RR, 1.02; 95% CI, 0.71-1.46).

In analyses stratified by age, the relationship between IA mineralization and cartilage worsening was stronger among patients aged less than 60 years (RR, 1.95; 95% CI, 1.11-3.41) compared with those aged 60 years or more (RR, 1.03; 95% CI, 0.75-1.40).

The stages of OA during which mineralization becomes important have not yet been determined, which was cited as a study limitation. Additional limitations included reduced generalizability to populations with more severe structural disease and limitations in detecting smaller crystal deposits via CT.

Study authors concluded, “Further studies are needed to confirm the validity of dual-energy CT data and multi-energy photon-counting CT for the identification of different calcium crystals, which in turn may provide novel insights regarding effects of specific crystal types.”

This article originally appeared on Rheumatology Advisor