Look up the TUBOW in the book. Do a couple of box squat workouts with your standard stance. Then do a workout without the box to about 90%, videoing all your warmups to make sure your knee slide stays fixed.
I'm a 43 year old 6'4" 235 lbs male. Last year on an HLM program I moved my squat from 310 x 5 x 3 to 355 x 5 x 3 (missed the last rep on 360 when I had a sinus infection and lots of stress). I did this by gaining some needed bodyweight and at the end I was doing the 5,3,1 cycling mentioned in the Barbell Prescription on the heavy day to keep the 3x5 heavy day moving up.
I was very happy with the progress but started developing patellar tendonitis below my left knee to the point where it would wake me up when sleeping after 6 or 7 hours unless I take pain medicine before bed. It would also bother me when sitting in a chair more than 20 minutes if the angle between my hamstring and calf was more than 90 degrees.
Posting on the Technique forum Rip said I need to switch over to a box squat starting at 270x5x3 to remove my knee slide, by recording each set and rep and figuring out how to squat more bent over, with a more vertical shin and no knee slide in that left knee. I've learned how to do this, but not sure how to work towards getting away from the box in the squat. I'm doing HLM on the box squat, so at the point where it feels like I can't add 5 pounds next week on the heavy day at around 300, do I try switching over to a regular squat with the stretch reflex on the heavy day while keeping the box on the lighter squat days? Do I keep the slightly wider stance in the box squat when switching over to the regular squat? On the box squat each foot is about 1 to 2 inches wider than in the regular squat. Or do I need to deload significantly and try running up a linear progression on the regular squat?
Look up the TUBOW in the book. Do a couple of box squat workouts with your standard stance. Then do a workout without the box to about 90%, videoing all your warmups to make sure your knee slide stays fixed.
If everything goes well and with the TUBOW I can squat normally without pain, how long should I continue using it? Do I use it for a week or two and then stop using it if that goes well? Do I recheck every month or so especially when things start getting really heavy?
Use the TUBOW until you can identify your knee position. That's all it's for.
In my experience, isometric holds tend to help heal tendonitis. When I had some knee tendonitis, 3x 1minute wall sits everyday did the job. Just my experience though..
If it did work, then there would still be knee slide continuing to cause the same problem, unless you stop squatting altogether. The isometric holds might work for the general population that maybe gets tendonitis from running or climbing, but for us doing Starting Strength Rip's solution of using the box squat to not only help heal the tendonitis but also retrain the movement pattern to fix the knee slide seems to be a better solution. I think that removing knee slide might even allow the same person to squat more weight than they could with knee slide, since the energy leak at the bottom gets removed or at least minimized in comparison.
You misunderstand. Fix the underlying issue first then to help speed up the recovery do the wall sits. Healing comes from the blood and tendons get little flood flow; hence the slow healing of small tears which if damage is greater than healing causes tendonitis. The Iso holds help with the bloodflow to the tendons. Then again, I'm not a professional so I very well could be wrong.
If you fix the squat form problem and are squatting correctly, the squats themselves should stimulate the tendons enough to heal them without the need for wallsits. If not, the pause squats to a box and sitting even further back would be the next option. I've not tried isometrics for managing tendon pain. I wonder how they would work more generally.
Isometrics for pain makes sense though. In my mind, deadlifts use an isometric contraction of the back muscles more or less. And nothing has gotten rid of my back pain more than deadlifts. So it seems plausible it could help other areas too.
I've found isometrics work pretty well with tendon pain, at least for temporary relief. Slow, relatively heavy eccentrics work pretty well too and seem to promote healing. If used intelligently can reinforce proper form if that was the cause of the problem in the first place. I've used both in combination for rotator cuff tendinitis and just the slow eccentrics for quad tendinitis.