There are many causes of knee pain, which can be categorised into different age groups.  Broadly speaking, patients are usually young (children and adolescents), middle aged (30 - 60 years) and mature (50 years plus).  

Young patients commonly suffer injuries which may need a repair or reconstruction procedure, such as meniscal or ligament injury.  These can be time critical.

Middle aged patients can also suffer the same injuries as younger patients, but may also be making a transition into more degenerative conditions which may require joint preservation techniques.

More mature patients generally suffer with degenerative conditions which might warrant joint replacement.