Does Manual Therapy help with OA?

The answer is yes, at least according to this lit review.

The “data crunching” found that manual therapy, defined as any hands on treatment rendered, with (and without) exercise therapy resulted in reducing pain, improving function, ROM and physical performance in patients with knee OA, at least in the short term. 

Anwer et al., Effects of orthopaedic manual therapy in knee osteoarthritis: a systematic review and meta-analysis. J Physiother 104 (2018) 264-276.