One caveat before you go any further....this article is being written with the assumption that you have functional knees with no tears, loose bodies, or large cartilage defects directly affecting your knees’ function. If you have a generally “healthy” knee and are a relatively healthy person who continues to get knee pain that doesn't seem to go away, your answer might lie above and below.
To begin, I would start at the bottom…the foot! While walking, a normal foot distributes your body weight starting at the heel and then moves toward the great toe as the heel begins to leave the ground. During this process, some feet will start the transference of weight toward the big toe too early, which results in the arch of the foot collapsing prematurely. This type of motion is called overpronation, more commonly known as a flat foot. While running, jogging, or walking throughout the day, this process repeats over and over again, which results in unwanted stretching in structures through the foot and ankle. It also inwardly rotates the tibia, which causes unwanted stress around the knee. This consistent over-pronation and unwanted stress around the knee can result in common knee pathologies, such as Iliotibial Band (ITB) Syndrome; Runner’s Knee; or Patellofemoral Pain Syndrome (PFPS). The most important factor in all of this is repetition. The actual process of running is not what is creating the pain or damaging the body. The repetitive overpronation of the foot, muscle imbalances, and improper joint motion create a repetitive strain can cause knee pain.
But the foot is usually not the sole culprit (no pun intended), so it is equally important to look above the knee for potential problems that could be impacting your knee. The hip is a common area that gets overlooked by runners and walkers alike. Research shows that patients with ITB Syndrome have significantly weaker hip abductors (the muscles that move the leg out to the side) on the affected side compared to the non-injured side. In a recent study, 24 patients with ITB syndrome were analyzed and it was discovered that their hip abductors were 21% weaker on their affected legs. In a 6 week span, a rigorous hip exercise routine was implemented, and by the end of the 6 weeks, significant gains were seen in hip abductor strength, and 22 out of the 24 patients were completely pain free. The problem truly lies in the impact phase of running, which results in an unwanted adduction (legs coming toward each other) and internal rotation (knees rotating in toward each) of the femur. This movement of the upper leg into excessive adduction creates abnormal forces upon the knee. If these forces occurred once or twice, it would not affect the joint or soft tissue surrounding the knee, barring some sort of catastrophic event (i.e. ACL tear). However, due to the repetitive nature of running, jogging, and working out in general, this abnormal motion continues to happen over and over again, creating knee pain that is truly not the result of an actual “knee problem.”
The solution: Physical Therapy! Patients should get a thorough initial evaluation focused on determining the cause of their symptoms. Oftentimes a treatment plan will consistent of hip and core strengthening exercises, or foot and ankle strengthening exercises along with manual therapy to help return normal biomechanics of the muscles and joints. Once the lower extremity is working with better flexibility and strength, the knee pain disappears!