If you have patellofemoral pain syndrome, you probably already know the feeling well: a dull, aching pressure behind or around the kneecap that flares when you go down stairs, sit for long periods, squat, or run.

If you have been told you have patellofemoral arthritis, you have probably received the standard advice: lose weight, strengthen your quadriceps, avoid stairs when flared, and take anti-inflammatories as needed.

Inclusion body myositis has a way of being misread for years. The grip that quietly loosens, the stairs that become a calculation, the swallowing that starts to require concentration — these are not vague symptoms, but they belong to a disease that remains underdiagnosed, often confused with polymyositis or simply with aging.

If your kneecap has ever slipped, caught, or felt unreliable during ordinary movements — walking down stairs, landing from a jump, or even sitting for too long — you already know how disorienting patellofemoral instability can be.