Like many distance races, the Philadelphia marathon has experienced a significant increase in female participants over the past 10 years. The benefits of running are well documented, and include improved cardiovascular fitness, maintaining appropriate weight and body composition, as well as improved mood and stress relief. However, runners are highly susceptible to musculoskeletal injury, and females, in particular, have an increased risk of knee injuries.

One of the most common knee injuries is an overuse phenomenon called Patellofemoral Pain Syndrome or "Runner's Knee." This syndrome can present as pain behind or around the patella (knee cap) with running, climbing the stairs, and sitting with knees bent for prolonged periods. The cause is variable, but in most cases, it is due to a combination of individual and environmental factors.

Common environmental culprits include running on slanted surfaces or shoes that are too old. The increased incidence in female runners is likely due to some key factors:

1) Leg alignment – Women tend to have more of a "knock-knee" and flat feet alignment than men. This can contribute to landing mechanics that cause the knee to collapse inwards while running.

2) Loose joints – The ligaments and joint capsule in the female knee tend to be looser than in males. As a result the knee cap can slide around in the groove on the end of the thigh bone (femur) causing pain.

3) Weak hip muscles – Women tend to have weaker muscles around the hip and pelvis which results in the femur sliding under the knee cap.

4) Hormonal fluctuations across the menstrual cycle – There are receptors for estrogen on muscles, tendons and ligaments. Recent research has shown that the structure and function of these tissues changes throughout the menstrual cycle.

The good news is that Runners' Knee is easily treatable. A female runner with this type of knee pain should be evaluated by a sports medicine physician to determine which particular factors are playing a role. Treatment often includes skilled physical therapy focused on strengthening the hip and lower limb muscles, taping, bracing and making adjustments in running mechanics. It is often possible to train and compete through the treatment phase, but getting started as soon as possible can help make race day pain-free and enjoyable!

Read more Sports Doc for Sports Medicine and Fitness.