„I am 28 years old. For a year, I trained cross-fit (before that, I was anorexic and sports pulled me out of that problem). Additionally, I have hormonal imbalances caused by weight loss. In the second month of this year, I moved away for work. For weeks, I couldn’t sleep and was overly stressed until I started feeling terrible pain in my knees and legs. During that time, I didn’t train at all, my muscles weakened, and I gained weight.
Two top orthopedists said it’s minimal chondromalacia patellae, but I feel terrible pain. For the first month, I couldn’t even walk. I think it’s also tendonitis. Doctors recommend swimming (which helps) and cycling (while cycling, my quadriceps tighten a lot, which further tightens the knee, and I think it doesn’t make sense).
Do you have any program where I first relax the tissues and the knee, and then systematically perform exercises for the muscles to take over the joint function?“

Although without proper examination, I cannot definitively claim, there is a possibility that you are experiencing what is called central sensitization. Translated, your body, or rather the central nervous system, interprets usual sensory inputs such as tightness, stiffness, and minor pain as extreme pain. To clarify immediately, the problem is NOT in your head in terms of purely psychological issues of subjective interpretation. The process is similar to an allergy, where the body reacts to a benign stimulus with an extremely strong immune response. Thus, it is quite possible that your “warning system” reacts with severe pain to very small stimuli. If so, then a exercise program with very, very gradual increase in load could be helpful. To start, cycling WITHOUT or with minimal resistance for 15-25 minutes, with long and non-intensive stretching, every other day. Later, combine it with treadmill walking or outdoor walking. If you see that this approach is not helping, seek out a physiotherapist experienced in treating central sensitization.