The others already clarified it but I would like to add my experiences with tendonitis:
For years during highschool and university my forearms and wrists hurt and I was multiple times diagnosed with "chronic tendonitis". Not doing certain movements and resting would lessen the pain but as soon as I started it very slowly again the pain immediately returned with the same intensity. The pain also came with a little less intensity to my left hand (right is dominant), which didn't make sense since I did most of the bothersome movements with right (clicking, writing etc.). The explanation I usually got was that it comes from bad posture (shoulders too far in the front) which didn't make sense to me because I saw other people sitting like a croissant typing all day long more than I did. I couldnt accept that my body should be so much more fragile than theirs. When I learned about TMS it all made sense to me and the pain went 95% away in a matter of weeks and didnt return for more than 5%. When I noticed the 5% slowly coming back, I just didnt care for the pain (before I learnt about TMS I was very afraid of the pain) and applied TMS techniques which made the pain vanish in short time. That was 5 years ago. No relapse. You couldnt explain that "physically".
That doesnt mean that there is no tendonitis however. As I am writting this with my left hand I have a "real" "physical" Tendonitis in my right wrist. Not from typing or some other repetitive every-day activity with little force but from archery. I pulled 25lb with two fingers while my wrist was bent (instead of straight, for some reason I changed my movements) for 2 hours. That is a big strain, thats how "physical" "acute" Tendonitis happens. And it actually feels very different than what I always felt during the "chronic" Tendonitis. Now it really feels like an injury and it is swollen. The pain is constant on certain movements and doesnt wander around - two things TMS pain does. Good thing is that I know of TMS and thats why I am not afraid of it. I know it takes some 1 or 2 more weeks of rest untill its good again. If the pain then, after recovery, tries to come back again, then I know its TMS, cus thats what TMS does (look up the "Whiplash" Syndrome).
TMS theory doesnt deny injuries like Tendonitis. TMS is about the chronic pain that is wrongly labelled "chronic" x. Our bodies are strong, resilient and quick to heal - the biggest bone, the femur, if broken takes 6 weeks to heal completely. Now imagine: If all the chronic diseases and pains which Sarno lists as TMS were "real physical", would humankind have come that far?
TMS usually happens when an acute injury or symptom persist after resting it for the appropriate time. Thats when the injury doesnt make sense anymore in a physical way but probably does in an emotional way.