Hey Danny
Congrats on the Judo competition. It's impressive even without the OA and two hips surgeries.
About not kicking the heavy bag or pads to protect the metal devices. Is there guidance from surgeons not to do this at this point? I'm not too convinced that hard kicking has any affect on the hips.
I myself have OA in both hips and kickbox 3 times a week. The classes are the real deal and by a two time former WKA champ who retired with one loss. All practice man. A real journeyman. Intense.
To be honest hitting the pads or bags themselves never cause me any pain when doing most kicks. This suggests to me that the impact on the hip joint is low. My shins receives impact, but by the time the force reaches my hip, which is imbedded, I don't usually feel any shock or pain.
The exception is front thrust kicks or side kicks which can sometimes cause some soreness. This suggests to me the direct impact kicks cause hip damage.
Leg kicks, body kicks, head kicks, or any kind of round kick on the bags have caused me pain too, but this disappeared with ramping up physio exercises for hip strengthening.
The reason I mention this is because it seems to me that hip pain from certain activities with OA are an indicator of what stresses the hip post surgery as well. Not the same but it would stand to reason an indicator.
Not every persons' hips are the same. Just something to think about. . .
I also think that using a theraband around my knees and doing the "four corners" makes a big difference for hip protection: standing side leg-outs with different pronations; lying adductor movement that mimicks the guard; front leg raises with/without ball; rear leg raises. Single Leg Squats. It's probably a good idea to do these exercises post-op too and if it's possible to kick a heavy bag without much or any pain with OA than the impact on the hips might be regarded as low. Just something to consider.