A 70-year-old woman suffered a dislocated shoulder, bruising and a gash on her head when she was attacked by a burglar at her Grimsby home.
The woman was attacked by the man after she disturbed him in the garden of her home on Revesby Avenue at 0700 BST on Monday, Humberside Police said.
The man then forced his way inside the house and stole jewellery.
The woman is being treated in hospital for her injuries. A 47-year-old man has been arrested and is in custody.
After stealing a wooden jewellery box containing several items of jewellery the woman's attacker ran away, leaving her lying on the ground.
Police said the woman's condition was not life-threatening.
Det Supt Gary Peck, of Humberside police, said: "This is a shocking incident in which a vulnerable woman has been seriously assaulted.
"The incident has happened during daylight hours, albeit early this morning, however it is possible that this male would have been in the area acting suspiciously either before or after the incident took place.
"It is also likely that he would have left the area after the incident in a hurry carrying the wooden jewellery box, possibly with blood on his clothing, so he may well have been quite easy to distinguish."
Witnesses have been urged to contact Humberside Police or Crimestoppers.