Hi there

Sorry for delay in reply - I got a 4 month old and as you can guess, my life is consumed with him besides trying to get to work too!

It is really hard to tell without an exam what may be causing your knee pain. Although, posterior knee pain is a lot less common (i think) than anterior knee pain. One of the common causes of posterior knee pain is a BAkers cyst. Other possible causes of post knee pain can be from the hamstring tendons if the pain is not directly central but either medial or lateral. And of course, you can get post knee pain referred from back/ hip/ pelvis.

Re sub patella pain - you mentioned that the debridement was to help this prob. In my experience, most sub patella pain is due to patella femoral pain syndrome (PFPS) - such pain I am not sure is helped much debridement procedures tho I may be wrong. PFPS often responds well to quadriceps strengthening, VMO (Vastus medialis obliqus) retraining and taping during activity.

Often, it will be great if a specific dx can be achieved but in the absence of a specific one, knee rehabilitation still can go ahead. You need to work on the range (which you have been), and the strength of the knee muscles. Then also have to work in global lower limb biomechanics - there are many ways to do this my preferred method is to use a progressive series of weigthbearing exercises which will strengthen the knee muscles, but also improve on how the hip-knee-ankle work together in a closed kinematic chain.

You prob will benefit from an assessment of the knee structures - physios can assess the integrity of the ACL/PCL/MCL/LCL, Wikipedia reference-linkmeniscus, patellafemoral joint and overall stability of the knee to determine the extent of deficit in knee function.

Its a bit of a overload in info- hope it helps!

Elin