Hi @SportsBoy, there are multiple causes of knee pain which occurs after running. The most common knee pain generators after running for young people include the knee cap, the menisci of the knee or some of the tendons around the knee joint. Acupuncture may only be useful for some of these conditions. 

Specific to acupuncture, my recommendation is to get your knee checked either by a qualified medical doctor or acupuncturist and let them determine if your knee condition is something which can be truly treated by acupuncture. A thorough assessment will include a proper history and physical examination. Sometimes, it may include some radiological tests as well. 

Based on the clinical diagnosis, sometimes, there may be other simple solutions which they may recommend, which can even include specific stretching and strengthening exercises!