Looking for recommendations for a knee specialist in Singapore for my mum

My mum has been experiencing knee pain lately, especially when walking for a while or getting up from a seated position. She sometimes complains that her knees feel stiff too, and I'm starting to get concerned as it's affecting her daily activities. I think it's time to have her properly checked by an orthopaedic doctor. For those who have helped their parents seek treatment for knee pain, may I know which doctor you consulted and how was the experience? Would appreciate any recommendations. Thank you!