This is a complicated subject,
So I love it!
I will send you a different article on the topic and you will see that the link you sent was just a copy of the schematics from the original article.
Rectus femoris has a unique design.
Proximally it has two tendon origins.
The direct head from the AIIS makes its MTJ at the anterior surface of the muscle.
The indirect head makes its MTJ in the middle of the muscle.
Hence you have to think of it like a muscle inside a muscle.
I like a hotdog metaphor.
The direct head is like a hotdog bun and the indirect head is like the sausage inside it.
The most common injury is for the indirect head component to “deglove” from the surrounding direct head component and hence you get the bulls eye appearance. I watch the indirect tendon carefully as I scan down the muscle and it should be continuous right down about 3/4 of the way to the knee before it disappears. If i can see this “intramuscular extension” of this tendon is intact but there is a bulls eye appearance I call this a degloving injury.
In your excellent video (which I would love to use in my teaching material if you grant me permission) you can see the central tendon for quite a while and then it completely disappears with a haematoma filling the space , then it briefly re-appears again distally. What has happened here is the indirect head intramuscular extension of the tendon has failed and popped. Hence you get atrophy of the proximal muscle component of the indirect head as it has nothing to pull on.
This is a central tendon failure and a bad injury in terms of recovery time etc.
With a devolving injury where the central tendon stays intact it will heal much quicker and also will leave less deficit. If the central tendon fails it is much worse.
I use another metaphor to explain this principle to people.
Imagine we are having a tug of war with a rope between us and the rope is slipping through your fingers a bit as you pull, this is like the devolving injury. Now imaging the rope between us snaps and we end up flat on the ground with o rope left to continue, this is like a central tendon failure.
There is another MTJ to consider as well and that is the distal tendon. The distal rect fem tendon makes the most superficial laminate of the quadriceps tendon. f you follow it proximally the MTJ is formed on the POSTERIOR aspect of the distal muscle belly.
I hope this makes sense.
I will find the article and email it to you ASAP,
Steve