You ask for personal experience,mindyourmind. When responding to your message earlier, something rooted in personal experience did indeed come to mind and I thought of including it in my response. Owing to constraints of time, I did not include it. Whether or not it is indeed relevant to the issue you raise, I am not sure and leave it to you and to others on the forum to judge.
For a good many years, my main practice was a specific method of mindfulness of breathing which had been brought to the United Kingdom by Nai Boonman, then a bhikkhu. It was and still is practised and taught by the Samatha Trust, a trust founded by students of Nai Boonman.The trust was called "the Samatha Trust" because it follows the teaching of the Buddha in the suttas by valuing achievement of the jhaanas/dhyaanas as the basis for the development of insight, in contrast to the newer "dry insight" methods, which were and remain dominant in many contemporary schools of Theravada meditation practice, and which regard the jhaanas as distractions at best and as negative and highly dangerous obstacles to insight at worst. Nai Boonman was Ajahn Brahmavamso's first meditation teacher when he was still, as I think he puts it, a long-haired student at Cambridge way back when, and it was from Nai Boonman and sitting-practice in the context of the Samatha Trust that he first learned, before he was ordained, that development of the jhaanas is important. In practice, the method taught and practised within the Samatha Trust is samatha-vipassanaa.
Perhaps a year after beginning to practice in the context of the Samatha Trust, I went on my first week-long period of strict practice. I was rather proud of my ability to sit for what seemed to me to be long-ish stretches in a sort of half half-lotus position, in which the right foot rested on top of the folded crook of the left leg rather than fully on top of the left thigh. The ability to sit in this fashion for forty minutes or so at a stretch had been achieved by dint of persistance and quite a bit of effort.
Each of us had an individual room in which each of us did most of our practice, alternating sitting meditation and mindful walking. Each person would report to a leader of the retreat once every day, the only time one would actually talk; we would gather for a light breakfast and for a meal before the sun reached the mid-point of the sky each day, and all of us would meet for a Dhamma talk and a communal sitting each afternoon. Otherwise, it was solitary alternation of sitting and mindful walking from the early hours of the morning until late at night.
As a novice to this kind of Theravadin strict practice, I found the first two days unproblematical. On day three, however, I began to discover that knees had rather alarming properties. Catching a glimpse of someone sitting in the garden within sight of the window of my room made it clear that I was not alone in discovering this: the person in question was ending a session of sitting-practice, and the painstaking care with which he unfolded his legs ever so slowly said volumes. Fran, who gave the Dhamma-talk that afternoon, began by simply saying "knees" and saying no more. There were sounds of slow, painful and nervous movements throughout the hall in response, as well as muted and decidedly nervous giggles. The word clearly struck sensitive nerves.
Most people managed to work through the painful sensation by some time the next day; but being a fully paid-up and card-carrying wimp, I did not. My sittings were plagued by terrible pain, egged on by even more terrible images and fears, which broke down my ability to sit almost completely. "Pain is a mechanism with an important physical function", I would find myself thinking. "It is a signal that harm is about to be done, and is meant to get one to stop doing whatever is causing physical damage." Images of needle-sharp crystals of uric acid lacerating the knee-joint loomed large, as did fears that I would do myself irreparable damage if I held my posture. And so, I found myself holding my posture for shorter and shorter periods -- at its worst, probably just a minute or two, breaking my posture and then forcing myself back into it. It was really a double-whammy: there certainly was physical pain, but anxiety about it -- attachment and aversion, and seeing the pain as a something an "I" -- namely me -- suffered, magnified it manyfold. It wasn't just that it was "eina", to use a South African word of Khoi-San origin for "ouch", but that I was attached to the "eina" and fretted over it.
The breakthrough came some time during day five, when I somehow found myself looking at the sensation in my knees with dispassion. There was a flux of sensation and I knew intellectually that it was pain, but somehow the "eina", the "ouch", was no longer there. It was just sensations rising and passing away, and the emotional investment -- the aversion and the fear -- vanished when one saw the sensations simply as sensations, as experience without an owner. This was actually quite disturbing at first: the pain had been unpleasant, to be sure, but it was mine. Where had it gone too? Had I been robbed? At some level, I came to realise, I had been attached to the pain. And so, initially, I probed my knees mentally, as it were, twinges of the "eina" came back, and I actually found this somewhat reassuring at first. Soon enough, however, the sense of strangeness disappeared, and one was left simply experiencing the arising and passing of sensations dispassionately without any sense of "this is mine" or "this is me" and, importantly, at least temporarily free of the grasping which is characteristic of dualistic vision.
It was a modest lesson. Others who participated in that strict practice probably went on to work through the far more subtle unpleasant feelings as distinct from grosser physical sensations, and perhaps also worked through the pleasant feelings which are an even tougher nut to crack. Perhaps some tasted jhaana or some of the jhaanas -- who knows? What I do know is that I got nowhere near jhaana, and that for me the strict practice was dominated by working through the pain exacerbated by my own attachment and propensity for seeing sensations as personal property, as it were, rather than as just arising and passing away, perhaps a play of energy in which subject and object have no purchase. A lesson I learnt: seeing experience as it is, without attachment and without aversion, the "eina" -- dukkha, really -- loses its purchase. When this is fully integrated -- something I was patently not able to do ... well, I'll leave it to you to draw the conclusion and to judge whether it is relevant to your query, or whether it is way