What Causes Patellofemoral Pain Syndrome and Chondromalacia?

I got this question recently.

It’s a good one because, unfortunately, the answers aren’t easy. But they are important to seek out. As I mention in Saving My Knees, my first law of healing is:

Before devising a plan to heal, you need to know what’s wrong and what’s causing it to be wrong.

So let’s start with what causes patellofemoral pain syndrome (often abbreviated “PFPS”).

Ah, that’s easy! It’s psst ... psst ... psst.

Seriously: there are two ways to answer this question.

One is that no one knows what causes it. No one knows because no one can know. There is no such thing as PFPS. PFPS is an overly broad, useless pseudo diagnosis that, when translated to its constituent parts from the bewildering medical terminology, means:

You have knee pain (of unknown origin).

An analogy: Your elbow hurts. You see me, a learned doctor, and I say, in tones most grave and dignified, that you have “humeroulnar pain syndrome.” You leave my office, distraught, then do some research, and find out that I’ve told you:

You have elbow pain (of unknown origin).

Not too helpful, huh? Same with PFPS.

The second answer is a bit more sophisticated. PFPS does mean “knee pain,” but it does align with a certain set of symptoms (difficulty sitting and walking up and down stairs, for example). So what’s the most likely cause of that symptom set?

In a moment, I’ll offer an, um, “unified theory of chronic knee pain.”

But first, let’s look at chondromalacia in the knee joint. What is that? It’s an abnormal softening of cartilage. That literal definition is rather abstract though. More commonly, it can be thought of as “a condition in which the cartilage ... becomes worn from age or is damaged from injury.”

Now there's one more thing to introduce at this point: patellofemoral pain syndrome and chondromalacia are often used interchangeably. They are NOT the same thing, but the fact that this confusion exists is very interesting. It suggests that one (chondromalacia) may have something to do with the other (PFPS).

Which brings me to a unified theory of chronic knee pain.

Cartilage problems are involved in much of this kind of pain. So bad cartilage would be implicated in many cases of PFPS. What causes bad cartilage, or chondromalacia, in the first place? I doubt there’s a simple answer. It could be anything from an injury to overuse to obesity -- whatever causes wear or damage to the tissue.

Next week: Objections to the unified theory. A response to each objection. Finally, even if bad cartilage isn’t causing your knee pain, why it may not matter in terms of what you need to do to get better.