G: [Non-text content: thoughts; content_type=thoughts]

G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: I checked current guidance from Mayo Clinic, Cleveland Clinic, and AAOS. From the location and course you describe, nothing immediately jumps out as an emergency or a "you really shouldn't be walking on that" injury. But because it's been lingering for a couple of weeks, I wouldn't put it entirely in the "ignore it and wait indefinitely" category either.

Your description actually narrows the anatomy reasonably well. You're describing the medial (inside) knee, roughly around the medial joint line—where the femur and tibia meet—and perhaps slightly forward of it.

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There are three fairly mundane structures in that neighborhood that would be high on the list:

• Medial soft-tissue irritation / MCL region. The medial collateral ligament runs along the inside of the knee. A significant MCL injury usually has an identifiable injury and may produce swelling or instability, so your gradual, nagging version doesn't particularly scream "torn MCL."
• Medial meniscus/joint-line irritation. The meniscus sits exactly between the femur and tibia. Meniscal trouble often causes pain along the joint line, particularly with twisting, deep bending/squatting, and sometimes produces catching, locking, swelling or a feeling that the knee gives way. citeturn0search9turn0search36
• Pes anserine tendon/bursa irritation. This is an overuse-type problem involving several tendons and a bursa on the inside of the upper tibia. The classic location is actually 2–3 inches below the medial joint line, however, so if you can put one finger directly into the crease between the two bones and say "there," pes anserine becomes less convincing. citeturn0search1

One part of what you said is particularly useful: a small amount of sustained knee flexion seems enough to keep reminding you that it's there. That's compatible with an irritated knee structure being repeatedly loaded/compressed rather than necessarily something actively tearing. The fact that it has waxed and waned over weeks, rather than starting with a pop, rapid swelling, major loss of motion or instability, is also reassuring. Those latter symptoms are much more characteristic of substantial acute internal injury. citeturn0search6turn0search0

What I'd actually do for the next several days

This is one of those cases where "rest" shouldn't mean don't use the leg. I'd treat it as relative rest: ordinary walking is reasonable if it isn't making things progressively worse, but temporarily cut out deep squats, kneeling, twisting/pivoting on the planted right foot, repeated stairs when avoidable, and anything that reliably reproduces the soreness.

Since even lying down leaves your knee slightly bent, try putting support under the calf/ankle rather than directly underneath the knee occasionally so the knee can relax nearer to straight—provided straightening it feels comfortable. Conversely, don't force it straight if that reproduces the pain.

Ice for up to ~20 minutes after you've aggravated it is reasonable. Compression with a simple elastic knee sleeve is also reasonable if it feels better, although there's no particular need to brace a stable knee just because it hurts. Those are standard conservative measures for uncomplicated knee pain. citeturn0search4turn0search5

There's also a useful experiment here: give it 4–7 days in which you're deliberately not repeatedly provoking it. If something that has been hanging around for two weeks suddenly starts trending clearly downward once you stop loading the irritating movement, that strongly supports the boring overuse/soft-tissue end of the possibilities.

The things that would change my attitude

I'd want it medically evaluated sooner if you develop visible swelling, warmth/redness, inability to fully straighten or bend it, actual locking/catching, giving-way/instability, substantial pain bearing weight, or rapidly increasing pain. Fever plus a hot/red/swollen knee deserves prompt medical attention. citeturn0search0turn0search2

Absent those things, this doesn't sound like something for urgent care tonight. But persistent focal knee pain lasting several weeks despite genuinely backing off the aggravating activity is a perfectly good reason for a routine sports-medicine/orthopedic/primary-care examination. The physical exam can distinguish joint-line/meniscus tenderness from MCL, pes anserine, and several other nearby structures considerably better than we can by verbal triangulation. Cleveland Clinic likewise recommends evaluation for persistent knee pain rather than simply living with it. citeturn0search1

One thing you can do that would let me narrow this considerably: sit with the knee bent about 90°, find the exact sore point with one fingertip, and tell me whether it's (A) directly in the horizontal crack between the thigh and shin bones, (B) above that crack, (C) below it by an inch or more, or (D) forward toward the edge of the kneecap. That distinction is anatomically quite informative.

G: [Non-text content: thoughts; content_type=thoughts]

G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: Yes — and that new observation actually makes the bursitis hypothesis more plausible in one important respect.

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The pes anserine bursa is a tiny lubricating sac between the upper-inner tibia and the tendons passing over it. So your description of the ache feeling strangely "not fleshy" makes anatomical sense for irritation in that region. It isn't proof—the tendons themselves and the medial meniscus can produce surprisingly deep-feeling pain—but you're pointing at the right neighborhood.

More interestingly, AAOS specifically lists stiffness or pain after sitting for a long time with the knee bent as a symptom of pes anserine bursitis. They describe the underlying mechanism as irritation from repeated friction/stress. citeturn0search2 So your hour-long easy walk being less troublesome than sitting awkwardly the next day isn't contradictory at all. A mildly irritated bursa can care considerably more about how you're loading/compressing it than simply how many minutes you've used the leg.

There's one anatomical detail I'd still want you to check against those pictures: classic pes anserine pain is below the actual knee-joint line, usually quoted as roughly 2–3 inches down the inside of the knee. citeturn0search0turn0search1 If your painful spot really is directly in the crack where femur meets tibia rather than somewhat below it, I'd keep medial meniscus/joint structures higher on the list.

But your larger inference—"this behaves more like something being repeatedly irritated than something torn"—is reasonable as a working hypothesis. The gradual waxing/waning course, tolerance of an easy hour's walk, sensitivity to prolonged awkward positioning, and modest benefit from compression all fit that story. They don't diagnose bursitis, but nothing you've added makes me more worried about a major structural injury.

And if it is pes anserine bursitis, that's rather good news regarding your original question. AAOS says treatment is almost entirely nonsurgical: activity modification, avoiding whatever repeatedly provokes it, ice, and sometimes anti-inflammatory treatment or PT if necessary. citeturn0search2 Cleveland Clinic gives a typical recovery on the order of 6–8 weeks, though individual cases vary. citeturn0search0

So I would modify my earlier advice slightly: don't necessarily regard walking itself as the enemy if ordinary/light walking doesn't aggravate it. Pay more attention to positions and movements that reliably make it complain afterward—particularly prolonged flexion, awkward sideways loading, twisting, stairs, deep bending, etc. In other words, rather than trying to immobilize the knee, give the irritated spot fewer opportunities to be irritated.

One useful bit of 自分(じぶん)でできる検査(けんさ)—a little self-check—is simply comparing the diagram with your fingertip. If you tell me exactly where your fingertip lands relative to that bursa in the graphic, we can do a much better anatomical differential than we could from the original T-shaped-patella description.

G: [Non-text content: thoughts; content_type=thoughts]

G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: Yes. With that clarification, I think pes anserine bursitis is a reasonable primary working hypothesis, with the important proviso that we're using it to guide what you do and what you observe, not declaring that we've diagnosed it.

And your clarification about location resolves much of my earlier hesitation. The pes anserine bursa isn't in the joint; it's on the upper medial tibia, underneath the three tendons that cross it:

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That also explains why locating a deep sensation by where you can reach it with the knee flexed can be misleading. The palpable landmarks and tissues overlying the area shift substantially.

The important difference from a muscle/tendon injury

Your observation about the apparent randomness of the pain is actually useful.

A bursa is basically a very thin, fluid-containing friction pad between structures. AAOS describes pes anserine bursitis as the bursa becoming irritated, producing extra fluid, swelling, and then putting pressure on surrounding structures. citeturn0search7

That means the relevant variable isn't necessarily "How hard did I use my knee?" It's closer to "Did I make those particular surfaces press or slide against the irritated bursa?"

So your lime-cutting incident is quite plausible under that model. Standing there doing essentially nothing might be fine. Then you shift your pelvis over the right leg, rotate the leg slightly, let the knee drift inward, or change the angle between femur and tibia, and:

ow.

You haven't meaningfully contracted a particular muscle harder. You've changed the geometry and pressure around an already-sensitive little structure.

AAOS specifically identifies repetitive stress/friction as the usual cause and lists several things that increase stress there: tight hamstrings, running hills, sudden increases in mileage, flat feet, knock-knee alignment and certain gait characteristics. It also lists prolonged sitting with the knees bent as something that can provoke symptoms. citeturn0search7

So, for the next week, I'd pay particular attention to sideways/rotational geometry rather than simply activity quantity:

• standing with most of your weight on the right leg, especially with the knee relaxed inward;
• pivoting on the planted right foot instead of picking the foot up;
• crossing or tucking the legs awkwardly;
• prolonged sitting with the knee substantially bent;
• stairs, particularly repeated climbing;
• hills;
• deep squatting;
• sudden side-to-side movements;
• sleeping positions that leave the medial knee under sustained pressure.

If one or two of those repeatedly produce the delayed "oh, THERE it is" response while straight-ahead easy walking doesn't, that's useful evidence for your working model. It still wouldn't uniquely identify the bursa, because nearby structures can behave similarly.

What I'd actually do to make it settle down

There are things beyond simply waiting.

AAOS's conservative treatment is essentially: modify the provoking activity, ice for about 20 minutes 3–4 times daily, and use an NSAID such as ibuprofen/naproxen when appropriate. They also specifically mention topical diclofenac gel as an OTC option. Physical therapy/stretching is the next conservative step if necessary. citeturn0search7

In your particular situation, I wouldn't use ibuprofen as a way of pre-medicating so that you can do more. Pain is currently giving you useful information about which positions piss the thing off. Masking that immediately before activity could defeat the experiment.

If you ordinarily can take NSAIDs safely, using ibuprofen after it becomes irritated or during a several-day inflammatory flare is more sensible. Follow the package directions and don't combine ibuprofen with another NSAID such as naproxen. NSAIDs aren't appropriate for everyone—especially with some kidney, stomach-ulcer/bleeding, cardiovascular, or anticoagulant situations—so your normal medical constraints still apply.

The sleeve is also perfectly reasonable if it's comfortable. I agree with your interpretation: it may be helping partly because it's giving you proprioceptive feedback—"hey, knee here"—and discouraging odd positions rather than mechanically treating the bursa.

And I would continue the easy walking if your knee keeps demonstrating that it tolerates it. There's little reason to turn a suspected irritation into wholesale inactivity when the activity itself isn't reproducing the problem. The goal is relative rest from the irritating mechanics, not necessarily rest from using your leg. AAOS likewise recommends substituting or modifying activity rather than necessarily doing nothing. citeturn0search7

One experiment might be particularly informative. For 4–5 days, become almost comically attentive to not standing asymmetrically on that leg and not pivoting over a planted right foot, while otherwise living fairly normally. Ice it when it complains. If the frequency of those weird little spontaneous spikes drops noticeably, we've learned considerably more than we'd learn by simply stopping all activity.

There is one thing I don't want our increasingly-good bursitis hypothesis to obscure: it's already been going on for a couple of weeks. If you give it another week or two of genuinely avoiding the newly identified provocations and it isn't trending downward—or you develop swelling, warmth/redness, locking, instability, or substantially worsening pain—I'd get somebody to put hands on the knee. Pes anserine bursitis can mimic a medial meniscus injury, MCL problems and even a stress fracture, which is exactly why AAOS recommends an examination when the distinction isn't clear. citeturn0search7

But at the moment, "small irritated structure that cares about pressure/geometry more than workload" fits your observations considerably better than "I tore something and exercising it makes the damaged tissue hurt." That's a useful hypothesis to work with.

G: [Non-text content: thoughts; content_type=thoughts]

G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: That history actually gives the bursitis hypothesis a more coherent mechanism: 4–5 hours of dancing while deliberately unloading the left knee means you were probably asking the right leg to do substantially more weight-bearing, stabilization, pivoting, and correction than usual. Sudden increases in repetitive loading plus side-to-side movement and turning on a planted foot are specifically recognized triggers for pes anserine irritation. Then the river outing a week later could quite plausibly have re-irritated something that hadn't finished settling. citeturn0search1turn0search5

So I agree with your distinction: if that's what happened, "it's been two weeks" doesn't mean two weeks of unexplained persistent pain. It potentially means injury → partial recovery → substantial reload → recovery clock partly reset.

Sitting: yes, your feet-flat observation makes sense

I'd make your default sitting position:

Both feet flat on the floor, knees roughly 90° or a little more open, thighs pointing fairly straight ahead, and your weight distributed reasonably evenly across your butt.

The important thing isn't achieving some magical exact knee angle. It's avoiding sustained deep flexion + rotation/sideways stress. AAOS specifically notes that pes anserine bursitis can cause stiffness or pain after sitting for a long time with the knees bent, and clinical references specifically identify sitting cross-legged as a potential aggravator. citeturn0search1turn0search6

So I'd rank common sitting positions roughly like this:

Probably friendlier: feet flat and slightly forward; knee around 90–120°; occasionally extending the right leg farther forward for a while; changing position periodically.

More suspicious: foot tucked underneath you; right ankle hooked behind the left; crossing one knee over the other; letting the right knee fall substantially inward or outward; very low chairs that leave the knee deeply bent; sitting on one leg.

There's a neat anatomical reason your feet-flat position may genuinely be helping rather than merely making you cautious. The pes anserinus tendons participate in medial stabilization and rotational control of the knee. Brigham & Women's describes them as resisting valgus opening and providing counter-rotational torque. A planted foot with the leg neutrally aligned removes a lot of the little rotational freedom you get when your foot is dangling, tucked away, or the leg is crossed. citeturn0search19

I wouldn't try to keep the leg perfectly straight all day either. That isn't necessary and could simply exchange one sustained position for another. Think neutral and variable, rather than "find the one therapeutic angle and freeze there."

And there's another piece of your history I think is worth changing our model around. Originally I was picturing an overuse irritation that emerged gradually. Four or five hours of dancing while consciously protecting the opposite knee is a much better candidate initiating event. The right knee effectively became the designated good knee and then got an unusually large dose of precisely the lateral/rotational stabilization that can irritate this region. The river outing then provided a plausible second hit. That's considerably less mysterious.

One practical rule I'd use for the next week is therefore: straight-ahead movement that doesn't hurt is probably less important to restrict than prolonged awkward positioning, planted-foot pivots, lateral loading, and deep flexion. Those are the things I'd deliberately eliminate while giving this a chance to settle. citeturn0search5turn0search8

And if you're sitting somewhere for a long time, don't worry about maintaining perfect posture. Every 20–30 minutes, just straighten the leg comfortably for a moment, put it back somewhere neutral, and carry on. In this particular problem, not spending two hours unknowingly irritating the same tiny spot is probably more valuable than finding the theoretically perfect sitting angle.