Pain beneath the kneecap is one of the most common maladies runners suffer. It can begin during the run but can get even worse after you finish. Going up or down stairs increases the pain in many cases, and there isn't always observable swelling. This type of knee pain, called patellofemoral syndrome, is perhaps most common during or after runs lasting more than an hour when your quads tire.
The patella is the bone that protects the front of the knee joint. Sitting inside the patellar and quadriceps tendons, the patella connects to the most powerful muscle group in the body, the quadriceps muscle group. The patella must withstand tremendous amounts of force, and that force is directly related to the forces that come from the quads. Sometimes, these quad forces play out undesirably. If a runner has a strong lateral (outer) quad, the patella can be pulled too far to the lateral side. How well-aligned the patella tracks up and down along the front of the femur also has to do with the thin layer of cartilage lining the back of it, the articular cartilage. Poor alignment or injuries to the articular cartilage are frequent causes of patellofemoral pain. Weak or tight muscles contribute because they will compromise running form. If your glutes, core muscles, hips, and/or quads are poorly conditioned, this can lead to pelvic instability, another major cause of knee pain.
Think of your pelvis remaining in a steady, level state as you run. If your muscles are under-conditioned, your pelvis may wobble, much like the wobbling of a car with bad wheel alignment. This puts stress directly on the knees, often leading to knee pain. Over-pronation, the excessive rolling of the foot upon foot strike, can also be rooted in this unwanted hip motion, explaining why orthotics can help remedy knee pain.
Patellofemoral pain is often quite preventable and almost always very treatable. If you cannot run without pain, and the pain is intense enough to alter your form, you should rest. This means cease running, but perform regular pool workouts, such as deep water running, and maintain vigorous upper body weight training. Riding a bicycle is helpful if it is pain-free.
Additionally, slowly begin to build up strength in your knees, quadriceps, and hips. Weak or inflexible quads are a major culprit of knee pain, since evenly built-up, strong quadriceps surround and lend stability to the knee. Targeting knees and hips in addition to the quads is the most effective strategy of all. Improved form will help to prevent the injury from returning in the future.
Poor running form often lies at the heart of knee troubles. Consider having a friend shoot a video of you on a treadmill so you can look at what aspects of your form may be hindering the smooth, forward motion needed to keep excessive pulling forces from overtaxing your knees. Hip weakness and over-pronation are certainly not the only issues that can undermine pain-free training. A good way to ease landing forces on the knees is to shorten your stride while increasing turnover. Aim for a cadence of 85 to 90 foot strikes on one leg for each minute of running.
If patellofemoral pain persists after more than two months of disciplined, home-based treatment, it's probably time to call the doctor. You may have a different problem after all, and an MRI is usually recommended. Patients over age 50 may have some form of patellofemoral arthritis where there is a wearing down of the articular cartilage that warrants professional medical attention, diagnosis, and advice.