Mr Guy devised (and published) the LIMP score as a simple tool to allow you to raise concerns that your knee injury does need knee specialist input. If you score positive for any of the statements below then it is possible you have suffered a significant injury that would benefit from a specialist opinion:

Leg given way during the injury or since
Inability to continue to play the sport
Marked swelling or bruising seen in / around the knee
Popping /snapping / tearing felt at the time of injury

First Aid
First Aid treatment of the knee should follow the P.R.I.C.E regime. Simple pain killers obtained over the counter can help in the initial days after surgery such as paracetamol and ibuprofen.

P – Protect the limb – Splint / Don’t walk on the limb
R – Rest
I – Ice the knee (Cover the skin always with a towel and ice packs or bags of frozen peas are great)
C – Compression – Stretchy bandages to help reduce the swelling
E – Elevate the leg.