Hi Mike,
This is a really typical Bakers cyst and they often wrap around the medial gastric tendon. You will see plenty more just like this. Check the subcutaneous fat just distal to the Bakers cyst in the medial calf for localised oedema which indicates a superficial rupture.
The knee has OA changes and CPPD in the meniscus as well as I think a likely meniscal tear as there is some cystic changes in the meniscus.
The joint effusion has the fronded appearance. This can be fat, but use the Doppler and if there is flow in it on a low flow setting with lot of gain it will represent synovial proliferation and knee joint synovitis.
Yes, you can check out the peroneal nerve apparatus.
I find the sciatic nerve in the mid / distal third of the posterior thigh. I follow it distally until I see the common peroneal nerve branch off laterally. Follow the CPD and the muscle on the lateral aspect of it is the short head of biceps femoris. This will guide you to the fibular head and you can watch the nerve pass around the fibula neck where it is usually damaged (most commonly from a fracture). It is also a rare location where an intra-neural ganglion can be found as they arise from the neural branch that enters the proximal tibia-fibular joint.
Steve.