First, start with the entrenched thinking (flawed) on what causes “patellofemoral pain syndrome.”
American Family Physician describes the cause of PFPS as an imbalance of the forces that keep the kneecap in alignment during knee extension and flexion. This imbalance can increase the risk of muscle dysfunction, poor quadriceps flexibility, overuse, trauma and a host of other musculoskeletal problems. In other words, during PFPS, the kneecap does not glide back easily on its “track” to the femur. ... Some health professionals, such as physical therapists and athletic trainers, recommend corrective exercise as a self-care method for patients.Sounds simple, straightforward, reasonable. Except:
Despite the prevalence of corrective exercise prescriptions, current evidence shows that this intervention may not always effectively treat knee pain and could be a waste of time.The problem is, the idea behind corrective exercise is that you’re crooked (your kneecap is mistracking) or that various muscles or tissues are too tight or too loose. But “studies have shown that PFPS may not always be a biomechanical problem.”
A 2006 Swedish study is then described, one that I was previously unaware of. Eighty patients with PFPS were examined. Of those, 29 had no identifiable cause of their PFPS (the others either had “slow bone turnover disease” or a type of pathology of the knee, and a small number dropped out.) For the 29 who didn't have a clear cause for their pain, “researchers could not differentiate between [them and] the control group that had no knee pain and were not diagnosed with PFPS.” So they weren’t identifiably crooked or imbalanced in a way that the control group was not.
Of course there is evidence that exercise can reduce knee pain, but as Paul Ingraham says in the article, that’s “probably not because it’s ‘correcting’ anything.”
I’ve linked to Paul’s website a few times over the years, such as to this essay where he examines the obsession that physical therapy has with crookedness/imbalances. I like his thinking and he’s a good writer. In the article above he is quoted saying, regarding the misalignment theory (the underlining is mine):
Exercises are prescribed in the hope that such things can be corrected, usually by strengthening and stretching. Unfortunately, a lot of exercising for these goals is often out of tune with how exercise actually does help patients.I couldn’t agree more with that. And, finally, he does well to note that knee pain comes in many stripes, with many possible causes. So, he notes:
Exercise is no kind of magic bullet. Patellofemoral pain has many faces, many possible causes and complications, and some cases do not respond to any kind of exercise, ‘corrective’ or otherwise.