Ins and Outs
The majority of tendinitis conditions affecting the lower leg and foot are felt along the medial (inner) side of the ankle (posterior tibialis tendinitis), the anterior or front of the foot (anterior tibialis tendinitis), and the posterior or hindfoot region (Achilles tendinitis). A small percentage of runners, however, may experience pain along the lateral or outer ankle region, just beneath and behind the bony protrusion of the lower portion of the fibula, also known as the lateral malleolus. The two tendons that traverse this region belong to the peroneal muscles, the longus and brevis. Like the other tendons listed above, they can fall victim to overuse injury that can disable a runner for weeks, if not months.
The peroneal (pehr-oh-knee-uhl: pronunciation can emphasize any of the first three syllables – take your pick) tendons are actually more often injured as a result of trauma than overuse; the typical ankle sprain can strain these tendons concurrently with the damage inflicted on the lateral ligaments. More significantly, a roll-out of the ankle can sometimes rupture the band of tissue that secures the tendons beneath the malleolus. When this happens, the tendons may become unstable and sublux or roll over the tip of the bone. This irritates and inflames the tendons, resulting in a chronic tendinitis problem. Not a good thing to have, but fortunately rare.
Peroneal tendinitis of the overuse variety is also fairly uncommon in the running population since the specific biomechanical conditions necessary to produce this injury are somewhat unique. The peroneus longus tendon, after it courses behind and underneath the lateral ankle, traverses across the bottom of the foot at the midway point, eventually attaching to the head of the first metatarsal (MT) bone – this is just before the ball of the foot at the great toe. The muscle’s function is to pull the head of the metatarsal toward the ground, so it effectively acts as a stabilizer of the great toe during the push-off phase of gait. Logic will tell us that a structurally unstable first ray (the first MT and some other bones attaching to it at its base) will necessitate extra effort on the part of the peroneus longus to ensure an efficient push-off.
The first ray can become unstable – meaning there is too much joint play due to lax or loose ligaments – secondary to trauma to the mid-foot, or from an excessively pronated foot. The latter causes this instability through its innate action of increasing mobility in the mid-foot. Normal pronation movement in the rear and mid-foot allows for normal mobility of the first ray; abnormal pronation may produce abnormal first ray movement. If such a condition exists, the obvious solution is to identify and correct the cause for the abnormally pronating foot. (As we have seen in the past, this may or may not involve orthotic intervention.)
Less obvious is the exact nature of lateral ankle pain in the first place. Distinguishing between the multiple structures in this part of the foot as the source for pain can be a tricky proposition. Runners who experience persistent discomfort along the outer ankle that does not respond to rest, icing, anti-inflammatory medications, etc., should probably seek professional assistance.