The 36-year-old Box Hill man was arrested today and taken to Prahran police station.
He is expected to be charged with assault and theft offences.
Penelope Katsavos, 78, was at the Saints Constantine and Helen Greek Orthodox church in South Yarra about 6.15am on Saturday when she was attacked.
Today, she was reunited with her husband in emotionally-charged scenes.
Thomas Katsavos, 83, lives with dementia and Ms Katsavos is his full-time carer.
Their son Evri Katsavos said it was an emotional moment.
“It was a very emotional moment … when dad saw her from afar then recognised who it was … he went up to her and gave her the biggest hug, that moment left us all speechless,” he said.
She was alone and injured for half an hour before a good Samaritan saw her and helped her.
Richard Pavlovsky was the council worker who found the injured grandmother and said he just wanted to make her feel safe after the harrowing ordeal.
“She was covered in blood everywhere, her eye was out here, her jaw was out there there was blood all over her clothes.
“I sat down next to her, put my arm around her, tried to embrace her keep her comfortable,” Mr Pavlovsky said.
Ms Katsavos was allegedly punched to the right side of her face and pushed down some steps before she became unconscious.
She has suffered a broken wrist, a hip fracture, significant bruising and bleeding to the brain.
At the time, her trolley bag, which doubles as walker, was taken during the assault – with her phone and cash inside.
The trolley was later located nearby with her things still inside.