The child is an eight year old with special needs ...... you say you have a special relationship with him ....so how does he behave with other people?
Is this a "one off" or is violence a normal reaction for him?
How does he behave at home??

If violence is part of his behaviour, it is important that a behaviour management scheme be implemented immediately. His parents must understand that a growing child whose violence is not curbed or contained is a danger not just too staff but to other children.

The reaction of his sister probably stems from over-protectiveness. Families can often become traumatised by the process of getting help for special needs children.

With regard to your injury ...you should definitely record the incident in the school's accident register in case this event added to the previous injury makes it difficult for you to work. If in pain, make a doctor's appointment and get the knee checked out and if necessary go on the sick until it is totally better. You could also contact the Union for guidance should something like this happen again or in case the parents refuse to cooperate.

Finally ..... don't take it personally - you were not responsible for the upset the child was feeling. He was probably kicking out in frustration at life in general not at you in particular. Accept that you are not a miracle worker and that there will be times when some situations are beyond you - don't let one incident damage your confidence in such a difficult yet rewarding job.

PM me if you would like to talk further or more privately. I am a retired Special Needs teacher who did the job for 30 years.