Hello, my left knee hurts when i run more than 5 miles. this happened first time 2 weeks ago. i run since jan this year, each week twice. ?

Too well done?: Don't over-do even good things. Before you do long-term damage, have an orthopedic/sports doctor examine it and follow recommendations for treatment, rest, support, etc. These injuries are common and most runners will describe their's if you ask. Gather and evaluate the 'wisdom' from others to keep you running a long time - but carefully!

See physiatrist: This may represent a meniscus injury or arthritis in that knee. See a physiatrist or orthopedist for an evaluation to see what to do to enable you to keep exercising.

Get checked: You may have a tear of the internal ligaments or cartilage. This can be common with running. An MRI can show more of these details. Your doctor may be able to prescribe medicines in the mean time. Good luck

The simplest...: Explanation is the most likely one. This sounds classic for an overuse injury. If you only have pain while running, and other activities are not bothersome, you don't likely have a serious injury and surgery not needed. See your primary care doctor for a focused exam. If needed plain films or MRI can be checked. Often this is treated with anti inflammatory meds and rest along with physical therapy