I started running around 6 months postop. I didn't attempt any formal running program, such as
Couch to 5k - C25K Running Program, nor did I ever give thought to proper foot wear or stretching properly. Ultimately, I paid the price when I developed what was originally thought to be runner's knee in my right knee. I was referred for physical therapy, which turned out to be an amazing experience! At my first appointment and initial evaluation, they deemed my problem was with my MCL (medial collateral ligament, the ligament that runs just on the inside of my knee) due to poor foot strike, falling arches, and improper stretching before and after running.
For one solid month, I worked with both a physical therapist and an athletic trainer to get me back in shape. They helped me develop a stretching and strengthening program. They suggested the use of orthotics (I bought some over-the-counter products to help with my arches and noticed a dramatic difference), as well as better running shoes. As others have suggested, consider getting fitted for running shoes...and track your miles on the shoes.
I was hesitant to attempt running while I was undergoing PT, but I decided to give it a shot and ran on Thanksgiving Day at my local high school track (mind you, I hadn't run for about a month). My first lap around the track, I noticed a slight pain in my knee. I immediately started thinking about my foot strike and how much I seemed to be guarding my knee. Once I corrected my foot strike, I noticed the pain went away. My knee started tightening up a little on laps 12 and 13, but I knew I was approaching my stopping point. I accomplished running 3-1/4 miles before heading to relative's homes for Thanksgiving dinner. My physical therapist about slapped me the next day when I went in for my PT appointment (she joked with me about how I was supposed to be slowing down to fully recuperate!), but she was thrilled that I was able to assess my pain and make corrections that helped me accomplish my run.
It's not easy being a runner, but it sure can be fun! There's nothing better for me than lacing up my shoes, turning on my iPod really loud, and heading out on the road. It's the only time of the day where I am free from home stressors, kid's whining and tattletaling, food (and all of my obsessive thoughts about calories, fat, protein, sodium, carbs, and fluids). Now that winter has arrived here in Michigan, I am giving serious thought to purchasing a running treadmill.
I hope your knee issue resolves and you are able to make some simple minor adjustments or changes. I tried running through my pain (mine had gotten so bad that my pain started as soon as I took my first step and didn't go away once I stopped running), but this only made my recovery longer. Don't make the same mistake I made. Ice it after your runs, and don't hesitate to make an appointment with your doctor. Better to be safe than sorry!