Why does knee pain so often start somewhere other than the knee? For decades, clinicians treated the knee in isolation — until dynamic imaging research revealed the real story: it’s often the femur moving under the kneecap, not the kneecap tracking poorly, that drives the pain. Dr. Brent Anderson sits down with Dr. Christopher Powers, professor and associate chair in the Division of Biokinesiology and Physical Therapy at USC, to unpack what that discovery means for how we understand and treat the knee.
Dr. Powers has spent his career studying the hip’s role in knee health, and in this conversation he explains “glute amnesia” — the surprisingly common phenomenon where patients simply can’t activate their glute muscles, even when they want to. He and Dr. Brent trace the connection from sedentary lifestyles and lost childhood movement patterns all the way to a troubling rise in ACL injuries among kids as young as ten. Along the way, they make the case for prevention, screening, and looking at movement — not just strength — as the real key to lasting knee health.
IN THIS EPISODE:
DEFINITIONS:
00:00 Introduction: The Knee Doesn’t Work Alone
A cold open on why the knee, hip, and ankle function as one connected system, followed by Dr. Christopher Powers’s introduction and research background.
03:38 Welcome, Chris — Diving Into Patellofemoral Pain
Brent and Chris kick off the conversation, framing the discussion around lower extremity organization and patellofemoral pain.
04:22 25 Years of Imaging Research
Chris revisits the dynamic imaging studies from decades ago that first challenged assumptions about patellar tracking.
04:59 The Femur Moves, Not the Kneecap
The revelation that in weight bearing it’s the femur moving underneath the kneecap, not the other way around.
05:31 Hip Control and the Femur-Knee Connection
Since the femur makes up half the knee joint, hip muscles are shown to control half of knee function by definition.
06:13 Old Habits: Patellar Taping and Its Limits
A look back at VMO exercises and McConnell taping, and why taping helped symptoms without fixing the underlying cause.
08:12 Redirecting Focus to the Hip
The conversation shifts to the exercises and observations that led to correcting femur alignment through the hip.
08:56 Glute Amnesia
Chris explains the concept of glute amnesia, where patients simply can’t activate their gluteal muscles on command.
10:08 Wrong Muscle, Wrong Signal
Why patients doing hip exercises often feel it in their hamstrings instead of the glutes, and the activation exercises developed to fix that.
11:59 Arthrogenic Inhibition and a Sedentary Life
How joint pathology and modern sedentary habits both contribute to the brain losing its connection to the glutes.
13:23 What Kids (and Squatting Cultures) Get Right
Infants and cultures that squat regularly retain natural hip mechanics that Western sitting habits erode over time.
15:13 Screens, Sedentary Childhood, and Lost Play
A discussion of declining physical education, screen time, and the disappearance of unstructured childhood play.
16:37 From Less Movement to the ACL Epidemic
Reduced movement development in kids collides with early organized sport, driving a rise in youth ACL injuries.
18:14 Anatomy 101: What the ACL Actually Does
A breakdown of the ACL’s role as the knee’s major stabilizer against rotational and shearing forces.
19:24 Hip Strength as a Predictor of ACL Injury
Research showing hip strength and control can prospectively predict future ACL injury risk.
21:04 The Long Shadow of Early Arthritis
ACL reconstruction is linked to early-onset osteoarthritis, turning a youth sports injury into a lifelong issue.
22:44 Rehab Requires Movement, Not Just Strength
Getting a weak muscle strong isn’t enough — patients also have to relearn how to use it functionally during movement.
24:16 Defining “Normal” Movement
Chris references Helen Hislop’s work on identifying what normal movement looks like across different populations.
25:51 Where Physical Therapy Falls Short
The profession’s overemphasis on isolated strength testing at the expense of evaluating movement itself.
27:01 Do Boys and Girls Move Differently?
Documented differences in how male and female athletes move, and why that may predispose girls to more knee injuries.
29:05 Prevention Over Treatment
Shifting the profession’s mindset from treating injury and pain to screening and preventing it in the first place.
32:04 The Red Flag: Knees Rolling Inward
Knee valgus is identified as the clearest, most observable sign of poor hip control to watch for.
34:04 Getting Coaches and Communities Involved
A call for youth coaches, parents, and physical therapists to bring simple prevention drills into everyday practice.
35:29 Take-Home Message and Finding the Right Clinician
Knee problems are a lower chain issue, and finding a movement-focused clinician is one of the best investments you can make.
38:01 Move Well, Give Back, and Closing Thoughts
A final call to prioritize movement quality, volunteer time for underserved communities, and Brent’s closing thanks to Chris.
PT, PhD, FAPTA
Christopher M. Powers, PT, PhD, FAPTA is Professor and Associate Chair in the Division of Biokinesiology and Physical Therapy at the University of Southern California. Internationally recognized for his expertise in human movement, Dr. Powers’ research has focused on lower extremity biomechanics and their relationship to injury, shaping evidence-based approaches to the prevention and treatment of knee pain, osteoarthritis, and sports-related injuries. He has published more than 200 peer-reviewed articles and has received multiple research awards from the American Physical Therapy Association. In addition to his scholarly contributions, Dr. Powers has been a dedicated leader within the profession. He has served as President of the California Chapter of the APTA and President of the Academy of Physical Therapy Research. Currently, he serves as a Trustee for the Foundation for Physical Therapy Research, where he continues to champion the profession’s scientific foundation and its capacity to improve patient care.
Get notified when new episodes are released and stay up to date with the latest insights on movement, rehabilitation, and Pilates education.
