Running is a stellar way to achieve top cardiovascular fitness, improve muscle tone and definition, lose weight and bolster your self-esteem. If you run on a treadmill, what you lose in variety you gain in being protected from the elements regardless of the weather, not having to endure the pounding of asphalt and concrete surfaces, and being able to set your speed with precision. Nevertheless, this doesn't make you immune to injuries, including those of the upper outer thigh.
Iliotibial Band Syndrome
The iliotibial band runs the top of your hip bone to the outside of your knee joint. The ITB, as it is more often called, is an extremely common source of pain among runners, both in the knee and in the upper thigh. Pain from a troubled ITB may shoot down the outside of your thigh, but it is usually localized closer to your hip.
If you frequently incline the treadmill belt to get in a "hill" workout, you are more susceptible to ITB pain. Sudden increases in training mileage are another common culprit. Treating ITB pain involves rest, icing, stretching and massaging the area that is most painful.
Any pain you feel in your outer upper thigh may be a consequence of an inflamed tendon. A large number of muscles attach to the pelvis, including the hip flexors, abdominals, the tensor fascia lata, and various muscles of the back and trunk.
The usual cause of this sort of tendinitis is weakness in one or more of these muscles, as this predisposes the tendons to inflammation, especially when a strength imbalance is present, i.e., when the muscle or muscles on one side are weaker than the corresponding muscles on the other. Strengthening your core muscles is likely to lead to recovery, and will make you a stronger athlete overall.
Also called athletic pubalgia or Gilmore's groin, a sports hernia occurs as a result of muscle weakness. It can cause pain on one or both sides; the discomfort usually most pronounced in the groin, but frequently radiates outward to the thigh. It is not a true hernia, which involves part of the lower intestine protruding through the abdominal wall. Instead, the pain results from inflammation of the adductor-muscle tendons that connect to the hips.
You are more likely to experience this problem when you accelerate rapidly -- not the usual situation on a treadmill -- or are simply doing more than your body is presently equipped to handle. Rest and physical therapy often help, but persistent sports hernias usually require surgical repair.
Inflammation of the pubic symphysis, a cartilagenous structure in the midline where your two pubic bones meet along your waist, is called osteitis pubis. This kind of pain is sharp, and can spread from its point of origin to your lower abdomen, down toward your groin, and outward toward either outer upper thigh.
Overtraining, a biomechanical imbalance such as a leg-length discrepancy, or both can bring on this issue. Resting, icing the area, and strengthening and stretching exercises can relieve the symptoms and, once the inflammation is resolved, help prevent it from happening in the future.
L.T. Davidson has been a professional writer and editor since 1994. He has been published in "Triathlete," "Men's Fitness" and "Competitor." A former elite cyclist with a Master of Science in exercise physiology from the University of Miami, Davidson is now in the broadcast news business.