Paul Kochoa is hardly the professional consensus and he does not reference a single study in his article. I am a certified specialist in orthopedic physical therapy and hold a doctorate just as Paul does. I also use research to back my clinical decisions and writing.

The leg extension machine is safe and effective. I use it frequently with my patients and have great success as do thousands of professionals in my field.

Here is the research, which is more objective than your experiences in speaking with a handful of health professionals.

Compliation of research showing they are safe and effective after ACL tears: https://www.jospt.org/doi/pdf/10.2519/jospt.2020.0609

The peak forces found in studies (https://pubmed.ncbi.nlm.nih.gov/9565938/) are not dangerous and help induce muscle growth. No studies show a causative effective of this exercise causing problems.

It is similar to misunderstandings about rounding the low back and posture. Both are assumed dangerous bit the research is clear they are not.

https://medium.com/in-fitness-and-in-health/rounding-your-low-back-while-lifting-is-not-dangerous-b760a337bccf

Brad Shoenfeld, one of the leading researchers in exercise physiology is an ardent supporter of leg extensions.

https://www.strengthzonetraining.com/are-leg-extensions-good-or-bad-safe-or-dangerous-effective-or-a-waste-of-time-functional-or-nonfunctional-exercise-expert-brad-schoenfeld-has-the-surprising-answers/

Unfortnately, this is a myth, like many in exercise, that won't go away. If you are going to look at expert opinion, you need a larger sample than your personal experience.

The leg extension machine is safe and effective.