DD has pain behind her knee

[varicoseveined]

I'm going to try to get a GP appointment for her this morning. She's 3.6 years old, and for the last week or so has complained of pain in her knee. At first I thought she was just copying what her grandma says (my mum has arthritis) or trying to get out of walking instead of using the pushchair, especially as she's fine at the playground and hasn't been limping or anything.

This morning though she has complained again and has indicated that the pain is actually at the back of her right leg and that it hurt since she went to soft play last week, and was wincing when she was trying to climb onto the bed. Has anyone else come across this?