Just an update. So I went to my local physio in March, who said she didn't think it was a Baker's Cyst and referred me to the GP. GP referred me for an MRI, the results of which confirmed it was a Baker's (phew!). Recommendation was to take ibuprofen, if in pain - I'm not, just mild 'sensation' of the lump being present.
So, for the last few weeks I've abandoned fellrunning to see if the cyst got smaller or better still disappeared. Usual exercise replaced with no (or comparatively little) weight bearing indoor rowing, 15K for 5 days each week, to feed my physical activity addiction (according to my partner!) and two days weekly fell walks, clocking up - slowly - ascent (2,550 - 3500) and mileage (14 to 18 miles) in the Hows and Lakes. Result: No change. Not a sausage
I now wonder if I should just 'go-for-it' and see if the cyst bursts, but potentially risk being in a more painfully situation, or.... admit defeat and erm take up something more sedate like, say, cycling (sorry - major tease - no offence meant)
! Seriously though, I've actually got to the point of thinking about dusting off and pumping up the tyres on my 1980s Peugeot Savoie tourer. That it should come to this...weep