Tight Quads no matter how consistently you stretch?

Stretching your quads properly, without lapsing into an arched low back, is tough.  Consistently tight quads have very much to do with chronic low back pain.  And, in the world of 'sitting syndrome', quads don't get much opportunity to lengthen!

One of the big reasons quads stay tight despite regular stretching is because your hips joints have shifted, which, in turn, shifted your pelvis [as demo'd in this video].  If you can imagine, a shift enough to maintain quad tension is a shift enough to perpetuate low back pain!

A way to work hip extension (you can add the quad stretch) combining mobilization of the hip.

Proper quad/hip flexor stretch -- you can add the mobility band (as per above) to combine it with hip joint mobilization

Per the pic, tight quads lend to more than just chronic low back pain.  Once you get 'locked' into this posture, manual physical therapy helps mobilize you when the self-intervention of mobility bands, stretching, and exercise have plateaued.

Basically, the rote belief of "you're getting old" or "it's arthritis" are NOT the reasons you have pain and relief is most definitely possible!

Best physical therapy dictates treating you AS A WHOLE dynamic, complex being... that means the joint ("pulley"), muscle ("lever arm"), fascia, areas above and below, etc. Intervention should be multifaceted and involve lifestyle change as well as manual intervention for restoring full mechanics of the pain area and surrounding regions!