They're all between 35 and 50 years old. They've all undergone surgery to repair a torn meniscus (a disk of cartilage in the knee joint). 87 percent of the group are aware of their knee problems at least monthly, and most have pain, stiffness and functional limitations.
Not a happy bunch.
They were subjects in a Swedish study to gauge the effect of exercise on something called "glycosaminoglycans" in knee cartilage. Big word, but important stuff: these polysaccharides are critical for keeping cartilage elastic and resilient.
The subjects were split into a control group (whose level of activity didn't increase over the course of the study) and a group that exercised. Each week, the exercisers were expected to go to at least three group classes, supervised by trained physical therapists.
The classes consisted of warm-ups, such as cycling, rope skipping and jogging on a trampoline. After that the subjects did "individually progressed weight-bearing strengthening exercises." These included such activities as repeatedly sitting down and standing up while holding a barbell bar (with no weight on it) and doing lunges while holding dumbbells.
After four months, researchers used a special enhanced MRI to peer into the joints of all the subjects.
The exercisers were found to have a significantly higher content of glycosaminoglycans than members of the control group. Also, they had improved scores on a special scale designed to assess pain, joint function and quality of life for people with troubled knees.
In Arthritis & Rheumatism (the November 2005 issue), the study's researchers, Ewa M. Roos and Leif Dahlberg, wrote that:
The changes imply that human cartilage responds to physiologic loading in a way similar to that exhibited by muscle and bone.So weak or damaged cartilage can change, and for the better. Furthermore:
In a cartilage matrix with low [glycosaminoglycan] content, as in cartilage disease, insufficient viscoelasticity may cause cause progressive denaturation of collagen molecules, collagen loss, and subsequent development of [osteoarthritis].Is having more glycosaminoglycans all that matters in beating knee pain? Of course not. But if you want robust knees that can withstand the rigors of daily living -- and that includes the "rigor" of sitting -- you need good, healthy shock absorbers, or cartilage. And good cartilage needs plenty of glycosaminoglycans to keep it stiff and functioning well.
So what the heck are glycosaminoglycans, and why do they sound so suspiciously like "glucosamine"? Ah, not a coincidence at all. I'll look at that next time, because answering the question properly requires a bit of a "fantastic voyage" into cartilage, on a cellular level.
(Note: observant readers will wonder about the exercises prescribed in the Swedish story. Aren't some of them "quad strengthening" -- which I've made no secret of disliking? Yes, but a few things: 1. They were done after a period of supervised warm up. 2. They were done under the supervision of physical therapists, who were monitoring each individual's form (a breakdown in form signals someone is doing an exercise beyond his or her capability). 3. They were specifically tailored to individual patients. 4. I'm not saying I endorse these particular exercises for knee pain sufferers; I'm just saying knees benefit from movement -- and here's evidence.)