Many conditions or injuries can cause pain in just one leg. According to the University of Maryland Medical Center, leg pain can be caused by blood vessel disorders, nerve problems, ligament sprains, muscle strains and joint pain. In some cases, leg pain is unilateral or occurs on only one side. This is especially true for traumatic lower extremity injuries, such as fractures or muscle tears. One-sided leg pain can range from mild to severe, depending on the cause of the pain.
Fractured Patella
A fractured patella, also known as a broken kneecap, can cause pain in just one leg. The patella is a triangular bone in front of the knee into which several tendons and ligaments attach. The patella increases the efficiency of the thigh muscles and absorbs a significant amount of stress between the thigh and the lower leg. The patella can fracture in several ways, according to the Cedars-Sinai Medical Center, a Los Angeles, California-based hospital and academic medical facility. It can suffer a partial fracture, a complete fracture or it can fracture into a few or multiple pieces. Common signs and symptoms associated with a fractured patella include severe one-sided knee and leg pain, swelling in the affected area, pain with knee active range of motion, difficulty performing a straight-leg raise and tenderness when the patella is pressed.
Calf Muscle Strain
A calf muscle strain or partial tear of the calf muscle fibers can cause unilateral leg pain. The calf muscles consist of the gastrocnemius, which is the bulky muscle at the back of the lower leg, and the soleus muscle, which is a smaller muscle that underlies the gastrocnemius. Both calf muscles help to plantarflex or point the foot away from the body. The calf muscles are one of the most commonly strained muscles in the body, according to the Sports Injury Clinic, an online information site, and calf muscle strains usually occur on just one side of the body. Common signs and symptoms associated with calf muscle strains include pain in the back of the lower leg, bruising and swelling in the affected area and decreased knee or ankle joint active range of motion. Strains, including calf muscle strains, are graded on a scale of one to three, based on the severity of the strain and the resulting symptoms. Grade one strains are the least severe.
Acute Compartment Syndrome
Acute compartment syndrome is a serious condition that usually occurs in just one leg. According to the American Academy of Orthopaedic Surgeons, acute compartment syndrome is a painful condition in which the pressure within lower leg muscles rises to dangerous levels. Increased muscle pressure can restrict blood flow, preventing nutrients and oxygen from reaching various tissues, including nervous and muscle tissue. If left untreated, acute compartment syndrome can cause irreversible muscle damage. Acute compartment syndrome may be caused by lower extremity fractures, severe muscle bruises, constricting bandages or anabolic steroid use. Common signs and symptoms associated with acute compartment include intense pain in the affected-side lower leg, numbness, tingling or burning sensations in the skin overlying the involved area and observable muscle bulging.
