Home > Uncategorized > How exercise affects knees: bone spurs vs. cartilage

How exercise affects knees: bone spurs vs. cartilage

July 30th, 2010

Conventional wisdom tells us that running and other forms of vigorous exercise will ruin your knees. A number of studies, on the other hand, have found that long-term runners are actually less likely to develop osteoarthritis in their knees than non-runners, as I’ve written about before. So how we reconcile these conflicting beliefs?

Australian researchers have just performed a large-scale analysis of existing research in an attempt to answer this question, in a paper that was posted online by Medicine & Science in Sports & Exercise earlier this month. They started by scanning 1,362 relevant studies, and eventually winnowed that number down to 28 high-quality studies (which gives you some idea of the number of lower-quality studies out there!). Six of them were MRI studies, with the remaining using X-rays to assess cross-sectional and longitudinal links between exercise and knee joint status.

Here’s what they found:

i) strong evidence (from multiple high quality cohort studies) that there is a positive relationship between osteophytes and physical activity;

ii) strong evidence (from multiple high quality cohort studies) that there is no relationship between joint space narrowing, as a surrogate for cartilage thickness, and physical activity;

iii) limited evidence (from a cohort study and two cross-sectional studies) that there is a positive relationship between cartilage volume and physical activity;

iv) strong evidence (from multiple high quality cohort studies) that there is an inverse relationship between cartilage defects and physical activity.

In other words, exercise results in fewer cartilage defects, and may actually result in increased cartilage volume, but also results in more osteophytes (also known as bone spurs).

So what does this mean? Bone spurs aren’t generally a good thing, but decreased cartilage (as measured by joint space narrowing) is the most common way of monitoring the progression of degenerative conditions like arthritis. The researchers suggest that, in this case, the bone spurs may simply be a reaction to the forces of exercise, and don’t indicate that the joint is degenerating:

Thus, in response to mechanical stimuli, such as physical activity, osteophytes may enhance the functional properties of the joint by increasing joint surface area for the greater distribution of load or reducing motion at a joint and improve joint stability… While it is possible the higher prevalence of osteophytes identified in people exercising may be detrimental to the knee joint, it could also be argued, in the absence of cartilage destruction, that physical activity is beneficial and osteophytes are simply a response to mechanical stimuli.

To be perfectly honest, it sounds like they’re stretching a bit to make things sound good. “What, exercise causes bone spurs? Well, maybe bone spurs are actually good for us!” But for most people, loss of cartilage is a far more serious consideration, so overall these results are (once again) good news for people who exercise regularly and don’t want to have to replace their knees when they turn 60.

  1. August 2nd, 2010 at 18:17 | #1

    I’d be interested to know if any of the studies you reviewed looked at the possible effects of biomechanical joint imbalances and dysfunctional movement strategies on osteophytes in the joint. If physical activity contributes to the creation of osteophytes as “a response to mechanical stimuli” – would optimal joint function not be important? If load is being transferred through the joint in a less than optimal way, and the ostephytes are being deposited where load/pressure creates greatest need for more bone – there is, I think, concern that the bone spurs could develop in areas that actually impede fluid motion of a joint over the long term. Whether or not joints “hurt” – I think it’s important to look at the movement patterning and load bearing strategies we bring to our movement to help prevent building spurs in places that could cause trouble later. Haven’t seen any studies that relates specifically to this – I’d be glad to know if you have. Thx!

  2. alex
    August 7th, 2010 at 02:14 | #2

    Interesting points, Sue. I think most people would agree that if you’ve got wonky joint angles that are applying uneven loads on your joints, that’s going to have consequences. Whether those consequences will turn out to be osteophytes is still just speculation at this point — I haven’t seen any studies along those lines. But I think it’s fair to say that we should all be aspiring to avoid excessively unbalanced joints!

  3. berto fernandez
    May 28th, 2013 at 06:08 | #3

    HELLO! I HAVE A FRIEND THAT HAD SURGERY RECENTLY TO REPAIR SPURS AND CARTILAGINOUS DEFECT. BEFORE HE COULD NOT EVEN PUT HIS OWN BODY WEIGHT ON HIS KNEE. HE HAD TERRIBLE BACK PAIN BEFORE. AFTER THE SURGERY, HE DOES NOT HAVE ANY BACK PAIN AND HE IS PUTTING WEIGHT ON HIS ANKLE AND HE FEELS NOT PAIN NOW. iS THERE A CHANCE THAT HE WILL NOT REQUIRE ARTHRODEDESIS. CAN THE CARTILAGOUS REPAIR ITSELF? HE IS REALLY CONCERN ABOUT THIS. THANK YOU

  1. July 30th, 2010 at 19:14 | #1
  2. October 13th, 2010 at 06:12 | #2