Why Hip Stiffness—Not Back Weakness—Might Be Causing Your Squat Pain.

One-sided low back pain during squats can come from a hip mobility problem rather than a spine problem. Dr. Aaron Horschig (Squat University) describes a patient who had right-sided low back pain every time he squatted for over a year. A chiropractor treated only the low back directly, but the pain kept coming back because the actual driver was elsewhere.

On testing, the patient showed hip stiffness moving knee to chest on his right side and a limitation in internal rotation of that hip. Because the hip couldn't rotate or flex normally, the low back compensated by flexing excessively during the squat, creating shearing forces across the spine. That compensation pattern—not a weak back—was the real source of his pain.

You test it by isolating spine position under load, separate from hip movement. Dr. Horschig had the patient pull up on a stool to load the spine in two different positions.

1. Neutral spine, pulling up on the stool — no pain at all.
2. Flexed spine, pulling up on the stool — this reliably triggered his symptoms.

This contrast confirmed the diagnosis: the patient's tissue was fine tolerating compressive load in a neutral position, but flexion under load was the trigger. Combined with the hip internal rotation limitation found earlier, this gave a specific movement diagnosis of flexion intolerance associated with a right hip mobility restriction — a term Dr. Horschig uses to describe pain driven by excessive spinal flexion compensating for restricted hip movement.

The fix combines hip rotation control, glute activation, and core stiffness — in that order. According to Dr. Horschig, this three-part sequence resolved the patient's pain in a single session.

1. Hip airplanes — used to regain hip rotational control, focusing on dropping the hip into internal rotation until a glute stretch is felt.
2. Side plank clamshell, held for 5 seconds — teaches the glute medius muscle to better control the newly gained hip rotation.
3. McGill Big 3 core stability routine, with 10-second holds in each position — enhances overall spine stiffness so the back doesn't need to flex to compensate.

After this sequence, the patient squatted 135 lbs with no back pain, the first pain-free squat he'd had in over a year.