Knee-Pain Triggers in Runners
By Sara Calabro
Runners are famous for investigating their injuries. Is it the surface? The shoes? The stride?
Answers to these questions don’t change the reality that runners endure a lot of pain, with the knees often bearing the brunt. And yet despite the high percentage of runners who are plagued by recurrent knee pain, effective treatment options are scarce within mainstream medicine.
Acupuncturists can assist runners with a new kind of investigation—identifying trigger points that cause runner’s knee.
What Is Runner’s Knee?
Runner’s knee is usually diagnosed as chondromalacia patella, suggesting damage to the cartilage under the kneecap. Another diagnosis is patellofemoral pain syndrome, indicating poor alignment of the kneecap over the femur. However, in a large number of runners, neither diagnosis fully explains what’s going on.
This is why runner’s knee, for many, is a chronic injury for which pain meds, icing, orthotics and other frequently prescribed treatments offer temporary, if any, relief. Many cases of runner’s knee actually are muscular in nature, caused by trigger points that refer pain to the knee.
The Quadriceps Muscles Are Likely Culprits
Trigger points in a number of muscles—hamstrings, gluteus minimus, and sartorius—can cause knee pain. But the most common culprit in runners is the quadriceps.
The quadriceps femoris muscle group includes the vastus medialis, vastus intermedius, vastus lateralis, and rectus femoris. With the exception of the vastus intermedius, whose trigger points usually refer pain to the mid-thigh region, trigger points in any of the quadriceps muscles can cause knee pain. A key to determining the affected muscle is having the runner identify the exact location of the pain.
Trigger points in the vastus medialis refer pain to the front and inner side of the knee. Since trigger points in other muscles can produce similar pain patterns, a tip off to the vastus medialis is if the runner also experiences weakness in the thigh and knee area, including buckling of the knee. Also, vastus medialis trigger points cause deep pain in the knee joint, leading to the common misdiagnosis of knee-joint inflammation.
Pain on the outer knee suggests trigger points in the vastus lateralis. This is the biggest of the quadriceps muscles, so trigger points can cause pain anywhere along the lateral thigh, as high as the pelvic area, down to just below the knee.
In addition to lateral knee pain, signs of vastus lateralis involvement include difficulty sleeping (since many people sleep on their sides, trigger points up the lateral thigh can cause pain at night) and posterior pain (the vastus lateralis is the only quadriceps muscle whose trigger points can cause pain behind the knee).
Vastus lateralis trigger points also can restrict patella movement, evidenced by difficulty flexing and extending the knee after sitting.
Although frequent offenders in cases of runner’s knee, rectus femoris trigger points are often missed because of their location. They usually appear near the proximal end of the muscle, on the upper thigh, around acupuncture point ST31. Trigger points in this part of the muscle refer pain directly to the kneecap.
The rectus femoris sometimes develops trigger points near the distal end of the muscle, just above the knee, but the upper portion is more common. Since pain in the front of the knee can also be caused by vastus medialis trigger points, palpation is the best way to distinguish rectus femoris involvement. In addition, runners might wake up at night with kneecap pain, as certain side-lying positions shorten the rectus femoris muscle.
For exact locations of quadriceps trigger points and their pain-referral patterns, Janet Travell’s Myofascial Pain and Dysfunction: The Trigger Point Manual is the consummate guide.
What About the Patella?
If quadriceps trigger points are so often to blame for runner’s knee, why do orthopedists, sports medicine doctors, and physical therapists talk so much about the patella? Quadriceps trigger points can be a primary source of knee pain, however, they also can cause pain indirectly by creating dysfunctional patella tracking (mentioned earlier as patellofemoral pain syndrome).
In Myofascial Pain and Dysfunction, Travell says, “Normal functioning of the patellofemoral joint depends largely on the dynamic balance between the medial and lateral forces exerted by the vastus medialis and vastus lateralis muscles.”
Trigger points disrupt this balance by shortening the muscles and making them tense, pulling the patella offline. Through trigger-point release with acupuncture, the muscles relax to their normal resting state and allow for proper movement of the patella along the groove of the femur.
Acupuncturists trained in trigger-point release can play a critical role in helping runners of all surfaces, shoes and strides stay healthy.
Photo by Sara Calabro