The peroneus longus muscle is part of the lower leg and is required to turn the ankle. It also helps to pull the ankle upwards, which is known as plantar flexion — something that is important for the stability of the knee as well as the ankle. There are three peroneus muscles located on the lateral side of the lower leg, although the longus is closest to the skin. The muscle is used in many daily activities, and it is most active while walking on uneven surfaces where it is required for stability.
The peroneus longus muscle originates at the top of the fibula — the smaller of the two main bones that make up the lower leg. From there it runs down the side of the leg and attaches to the bottom of the first metatarsal in the foot. It is part to the body’s nervous system via the superficial peroneal nerve. The other muscles in the peroneal group are the peroneus brevis and tertius.
Although the peroneus longus is associated with plantar flexion and eversion, or turning, of the ankle, it’s also essential for stability of the foot. Due to its location on the outside of the calf muscles, the peroneus muscle group is important when it comes to stabilizing the leg above the ankle. This becomes more apparent when standing on one leg — without the peroneus longus the leg would be drawn inwards.
Due to its importance as a leg stabilizer, the peroneus longus sometimes need to be strengthened. This is especially true for athletes who require a greater level of stability and control than most people. Strengthening exercises for the peroneus longus include calf raises with a bent knee. To perform these exercises, the athlete should stand on one leg on the edge of a step with his or her non-weight bearing leg behind the other. The heel is then lifted as high off the step as possible and held for several seconds before being lowered back down.
As with any muscle that is used in many daily activities, the peroneus longus can suffer from over-use injuries. For example, peroneal tendinopathy can affect the tendon which attaches to the muscle. Symptoms of peroneal tendinopathy include pain on the outside of the ankle, pain that gets worse during sport and extremely tight calf muscles. Treatment for this sort of tendinopathy includes rest, calf stretching and in some cases sports massage.