HIV infection and
antiretroviral therapy are associated with increased risk of cartilage
damage in the knee associated with osteoarthritis, according to the results of
a small US study published in BMC
Musculoskeletal Disorders
. The case-controlled study showed a higher
prevalence of several key markers of knee cartilage damage at baseline and
greater deterioration over eight years of follow-up.

“Our results
suggest that treated HIV infection is associated with compositional changes of
the cartilage matrix and increased knee joint inflammation, but findings appear
not to have a significant impact on structural knee degeneration,” comment the
authors.

Despite the small
study size (ten people with HIV and 20 matched controls) the study
had a rigorous methodology and hints that ageing HIV-positive people may
well have an increased risk of arthritis.

As well as ageing,
metabolic problems such as high lipids, hypertension, body fat disturbances and
diabetes can all increase the risk of osteoarthritis. Thanks to improvements in
treatment and care, many people with HIV now have an excellent life
expectancy, but the inflammation caused by untreated HIV and the side-effects
of some antiretroviral drugs can increase the long-term risk of metabolic
problems.

Dr Yao Liu and
colleagues from the US Osteoarthritis Initiative therefore wanted to see if people taking antiretroviral therapy (ART) were more likely than matched controls to have knee
cartilage degeneration and structural knee changes over eight years of
follow-up.

At baseline and
during follow-up, cartilage health and knee structure were assessed using an
intensive battery of tests including MRI imaging and measures of cartilage
structure, composition and texture.

The people with HIV and controls were closely matched for age, sex, race and BMI.
Approximately a third were female and the mean age was 52 years.

All the
people with HIV had been on HIV therapy for at least 12 months.

Baseline analysis
showed that the HIV-positive people had a higher prevalence of several
markers of cartilage damage, including fat pad abnormalities and higher knee
effusion (accumulation of fluid around the knee, a marker of inflammation)
scores, when compared to the controls. However, these individuals
were less likely to have a type of bone cyst associated with osteoarthritis.

Over the eight
years of follow-up, the ART group showed a significantly greater decline in
markers of cartilage texture and composition and also more severe knee
effusion. However, as at baseline, bone cysts were less severe in people with
HIV than the controls.

The investigators
believe their findings show “a more heterogeneous and disordered cartilage
matrix composition” in ART-treated people, adding that “cartilage damage is
the hallmark of knee osteoarthritis, and cartilage matrix degeneration is
an essential event that determines the irreversible progression of knee OA [osteoarthritis].”

A possible cause
for the cartilage degeneration seen in the ART-treated people is
HIV-associated loss of skeletal muscle mass around the knee, leading to changes
in the biomechanics of the knee and cartilage damage. Alternatively, the damage
and inflammation could be due to a combination of HIV-related inflammation,
treatment side-effects and metabolic disorders.

The investigators
were puzzled by their finding that the HIV group had lower bone cyst scores
than the controls and comment: “Given the complex effects of HIV and ART on
bone resorption and bone formation, additional mechanisms may be involved
reducing the development of subchondral cysts.”

The investigators
acknowledge that their study had a number of limitations, especially the small
sample size and call for further research to validate their findings.

“Our study showed
a more heterogeneous and disordered cartilage matrix composition in PLWH [people living with HIV] on
ART, suggesting that treated ART infection may accelerate the degeneration of
the knee cartilage matrix,” conclude the authors. “In addition, compared with
the HIV-negative group, PLWH had significantly more severe knee joint effusion
over 8 years.”

The clinical
significance of these findings will need to be confirmed by larger studies.
However, the analysis does underline the importance of assessing bone health
and arthritis risk as part of the routine care of ageing people with HIV.