For Happier Knees, Avoid Soda, Cigarettes

When we’re young and ridiculously healthy and generally pain-free, we beat up our bodies a lot. That abuse partly comes in the form of junk we stuff into our mouths (as a college freshman, I liked to go into an “all nighter” with a full box of Entenmann’s soft chocolate-chip cookies by my side -- a box that would be depleted well before sunrise).

Some of us drink too much. Some of us take up smoking, with little thought to the long-term consequences.

When we get older, we usually get smarter about the self-abuse. When we get older and injured, it’s wise to be especially careful about bad diets and bad habits.

Take something as seemingly innocuous as soda. A study by researchers at Harvard Medical School showed that drinking soda may worsen knee pain -- and not because the sugary beverage tends to pack on excess weight. Rather, according to this short article, “one theory is that ... chemicals in soda may affect bone health in joints.”

Or consider an activity that we all know is definitely harmful: smoking. Indulging in this habit has been shown to be bad for your knees.

The January 2007 issue of Annals of the Rheumatic Diseases included results of a study of 159 men (12 percent of whom started out as smokers) that looked at the relationship. The men who had knee osteoarthritis who also smoked  sustained “greater cartilage loss” with “more severe knee pain.”

The researchers wrote that the harmful effect of smoking on articular cartilage “may be greatest when cartilage is already damaged by other mechanisms.”

So what’s going on here, on a cellular level?

The authors note that investigations into smoking and back pain have found that “components of tobacco smoke have a deleterious effect on chondrocyte function in discs, inhibiting cell proliferation and extracellular matrix synthesis.” Remember, chondrocytes play a critically important role as the cellular factories that produce more cartilage.

In their discussion section, they expand further. A study on smoke-exposed rats showed “disordered chondrocytes” in their intervertebral discs. In a separate study, on bovines, nicotine inhibited the proliferation of chondrocyte cells and impaired their ability to make new cartilage.

What causes such problems?

For one, smoking increases oxidant stress, and “oxidant stress may contribute to cartilage loss.” Then there’s this: “Cigarette smoking also increases carbon monoxide levels in arterial blood, contributing to tissue hypoxia, which may, in turn, impair cartilage repair in smokers.”

What this all adds up to is clear. What you put into your mouth (or suck into your lungs) can matter a great deal if you have chronic knee pain.