Three muscles make up the section of the leg below the knee that most people call the calf. While any direct injury to these three muscles can cause pain, conditions that affect the surrounding tissue, arteries, nerves, or the muscles themselves can do so, as well.
Some of the most common causes of calf pain are muscle cramps, which are involuntary contractions of a muscle. Cramps can be extremely painful and even debilitating. The muscles may feel stiff to the touch or have a visible knot. Though the cramp may not last very long, the pain and soreness can persist for several days.
Another common cause of calf pain is muscle strain. Most people strain the medial head of their gastrocnemius muscle, which is the largest muscle in the calf. This condition is commonly known as “tennis leg.” Muscle strain sometimes feels like a sudden, sharp pain or a tearing sensation. Bruising and swelling are common. Severe strains may prevent a person from moving the affected leg.
Long-distance sprinters often damage their soleus muscles, which sit under the gastrocnemius muscle. People who incur this injury often describe the pain as a deep soreness or tightness. The sensations often worsen when bending the knee and pulling the toes toward the shin. Strains are more common, but full ruptures do sometimes occur.
A significantly smaller muscle runs alongside the gastrocnemius muscle. Movements such as lunging forward or dashing can place tension on this muscle, causing a strain or a rupture. This feels like a sudden, snapping pain in the calf. Sometimes, runners can even hear an audible pop as the muscle snaps. Cramping may occur soon after, along with bruising and swelling. Plantaris injuries are rare.
The legs are an extremely common injury site. The calves can become damaged from falls, collisions with objects, and strikes from other people. These incidents crush the calf muscles against the bone, leading to bleeding within the muscle. If the blood leaks outside of the muscle, it may become a bruise or other hematoma. If the blood remains inside the muscle, swelling may be the only visible symptom.
Claudication results when the muscles do not receive enough blood during exercise. Most people notice claudication after walking at a certain pace for a longer period than they would normally and experience mild to severe muscle pain. Claudication is technically a symptom of an underlying condition, such as peripheral artery disease. The pain often fades away after resting for a short time.
The sciatic nerve stretches from the lower back, through the hips, into the legs. If an issue like a herniated disk or bone spur compresses this nerve, severe pain may radiate along the nerve’s path. This condition is sciatica. One of the key signs of sciatica is pain that shoots below the knee, particularly when lifting the legs while lying down.
Achilles tendonitis is swelling resulting from an overuse injury of the Achilles tendon, which is the tissue that connects the calf muscles to the heel bone. Runners who recently increased the intensity or distance of their runs are particularly prone to developing Achilles tendonitis. The condition is also common among middle-aged athletes who casually play sports like tennis or basketball.
Some people develop fluid-filled cysts behind their knees. These Baker’s or popliteal cysts swell and can cause pain that radiates from the knee into the calf. Sometimes, the cyst bursts and leaks fluid into the calf region, resulting in sharp pain, swelling, and a sensation of water running down the leg.
Blood clots can form in the deep veins of the legs, usually as a result of an underlying condition or remaining stationary for long periods. This condition — deep vein thrombosis — often causes pain that begins in the calf and feels like soreness or cramping. Deep vein thrombosis is potentially life-threatening, as the blood clot may dislodge and travel to the lungs.
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