Leg Pain Causes

Trauma

Trauma is the most obvious cause of leg pain. Falls, near falls, and twisting injuries can damage bones, muscles, and joints or a combination of all three. Pain from an injury to the back can inflame the sciatic nerve and cause pain that radiates down the leg. Overuse injuries can cause pain as well and may be thought of as multiple minor traumatic injuries.

• Fractures: The terms fracture, broken, and cracked all mean the same thing when referring to a bone. It means that the integrity of the bone has been compromised. The most common symptom is pain which arises from the nerve endings located in the lining of the bone itself, called the periosteum (peri=surrounding +osteum=bone). As well, the muscles surrounding the bone go into spasm and intensify the pain.
  
  
• Sprains and strains: A ligament injury is called a sprain and occurs when the ligament fibers are stretched, or partially or completely torn. Muscles and tendons can also be stretched or torn, causing a strain. Both sprains and strains result in swelling and inflammation that causes pain.
  
  
• Bleeding: Injuries can also cause bleeding into tissues and joints. Since blood, like any fluid, cannot be compressed, the swelling causes significant amount of pain as the pressure increases.

Non-traumatic Leg Pain

There are numerous causes of non-traumatic leg pain, and there is no single way of classifying all of these causes. Health care practitioners develop individual approaches to help decide upon a diagnosis. Sometimes it can help to classify the potential causes based upon the part of the leg that hurts, whether the pain is in one leg or both, whether it is related to activity or occurs at rest, and whether underlying medical conditions exist that can precipitate leg pain.

Pain in only one leg would tend to be due to local problems and not necessarily due to a systemic (involving the entire body) illness. The presumption would be that such an illness would affect both legs. This is not necessarily always true, since gout (the body's inability to process uric acid) often attacks only one joint during an acute flare.

• Peripheral artery disease: Pain in one leg may be due to peripheral artery disease, a decrease in arterial blood supply due to narrowing of blood vessels to the leg. Often the pain comes with activity, since walking requires more oxygen for the muscles and if the arteries are narrow and can't supply that need, the muscles begin to hurt. Blood vessels can be narrowed at any level, from the aorta (the large blood vessel that leaves the heart), to any of the branch arteries. Depending upon the level of narrowing and the particular muscles involved, the areas of perceived pain may be different.
  
  

Leg pain from peripheral artery disease that occurs with walking is called claudication. Since peripheral artery disease usually affects many blood vessels, both legs may be affected. The blood supply may decrease to the point at which pain occurs at rest, even without exercise. Poor blood supply to the legs may also compromise the integrity of the skin and may allow infection to occur.

• Blood clot: A blood clot can completely obstruct one of the arteries to the leg and cause the acute onset of pain because the blood supply has been completely cut off. Aside from pain, the leg becomes cool and pale. While there are many potential sources of a blood clot, one common place to look is the heart. If the cardiac arrhythmia known as atrial fibrillation is present, there is the potential that small clots can form on the lining of the heart and break off to travel through the arteries, obstructing blood flow at points distant from the heart. Aside from the leg, the obstruction may occur in one of the blood vessels leading to the brain, causing a stroke.
  
  

Veins return blood from the legs to the heart. There are two systems of veins in the leg - superficial and deep. If a blood clot occurs in a deep vein (deep venous thrombosis), it causes a "damming" effect, and blood is trapped behind the blockage. This causes redness, swelling, warmth, and pain in the affected area. Superficial veins can also clot and cause pain, but the complication of a deep thrombosis (breaking off and embolizing to the lungs - pulmonary embolism) does not occur with a superficial thrombosis. Superficial veins can also chronically dilate and swell, known as varicose veins. Varicose veins may cause pain from this swelling and inflammation.

• Low back pain: Low back pain from sciatica (inflammation of the sciatic nerve) may radiate into the buttocks and down the leg. The distribution of pain depends upon which nerve root is involved; therefore the pain may be felt in the foot, shin, or thigh. Sciatica may be caused by a variety of changes in the back from arthritis, a herniated disc, muscle spasm, or injury.
  
  
• Neuropathy: Pain may occur from peripheral nerve inflammation not associated with the spinal cord. These conditions are known as peripheral neuropathies. This can occur from direct nerve irritation or from a medical illness. Examples of injury include foot and toe pain from a Morton's neuroma, most frequently a thickening and inflammation of a nerve that supplies the 3rd and 4th toes, or meralgia paresthetica that causes pain in the anterior thigh resulting from entrapment of a nerve that leaves the pelvis. Neuropathy is also seen in pregnancy when the pressure of the uterus may cause the nerve to become inflamed. These types of pain tend to involve part of one leg only.
  
  
• Illness: Chronic illnesses like diabetes, alcoholism, cancer, and vitamin deficiencies may also result in nerve pain that often affects both legs.
  
  
• Joint pain: Joint pain may occur because of a local injury but may also be due to medical conditions that can cause inflammation and swelling. Joint pain associated with swelling is called arthritis (arth=joint+ it is=inflammation), while pain without swelling is called arthralgia (arthr=joint + algia= pain) Some examples include the following:
  
  
  • Patients with progressive osteoarthritis may have days in which affected joints may hurt.
    
    
  • Similarly, patients with rheumatoid arthritis may have episodes of joint inflammation when their disease flares.
    
    
  • Exacerbations of gout can cause joints to become inflamed if uric acid crystals start to deposit within the joint. It is often the joints that are under significant workload that are affected. The joints in the great toe are commonly involved, but the ankle and knee are also common sites of uric acid crystal deposition.
    
    
  • Pseudogout can also cause joint inflammation. Instead of uric acid, calcium pyrophosphate crystals deposited in joints are the cause of this condition.
    
    
  • Systemic illnesses (there are too many to discuss in this article) may also cause joint inflammation. Some common conditions that may cause joint pain include systemic lupus erythematosus (SLE), psoriasis, hepatitis, inflammatory bowel disease, and Lyme disease.
    
    
  • Joints may become inflamed as part of the body's generalized reaction to an infection. Infections may cause synovitis, or inflammation of the synovium (the lining tissue of a joint). Most often it is due to a virus, but in children there is always a concern that a bacterial infection is the cause.
    
    
  • People who take warfarin (Coumadin) for anti-coagulation (to thin their blood) may spontaneously bleed into a joint, causing pain.
    
    
• Muscle pain: Muscle pain or myalgia (myo=muscle +algia=pain) is a common finding and may be due to overuse (mild trauma) or associated with the generalized aches and pain of an infection.
  
  
• Muscle cramps: Muscles may cramp, causing significant pain. This may be due to a lack of stretching or an imbalance of electrolytes in the bloodstream. The body needs to have the right amount of calcium, sodium, and potassium for muscles to function well. Calf and foot muscles are particularly prone to cramping, especially at night.
  
  
• Muscle injuries: The muscles in the leg tend to be in balance with each other to promote joint stability and act as shock absorbers for the forces that are generated by walking and running. The quadriceps muscles on the front of the thigh extend or straighten the knee and are balanced by the hamstring muscles in the back of the thigh responsible for flexing or bending the knee. If this balance is lost, the muscle fibers may become overstretched and tear. This is called a strain.
  
  
• Hamstring Injury: The hamstring is made up of a group of individual muscles known as the semitendinosus, the semimembranosus, and the biceps femoris. While the tendons can be felt at the back of the knee, the muscle originates and is anchored in the pelvis bone. When the muscle contracts, the knee bends and the leg is able to generate power to push the foot away from the ground so that the body can walk. Walking also requires the quadriceps muscles to fully extend the knee so that the heel of the foot can strike the ground and begin the footstep.

  If the hamstring muscle tendon units are not flexible or if there is too much stretch placed on the structure, fibers may be damaged if the knee extends too much. Muscle or tendon fibers may be stretched or even torn, causing pain and swelling. To protect itself, the muscle may go into spasm which may cause even more pain.
  

• Skin abnormalities: Skin abnormalities may cause pain. Lacerations and skin tears, ranging from trauma to ulcers caused by poor blood flow, are among the causes of pain from skin conditions. The skin has numerous nerve fibers that can sense pain, and anything that damages the skin can cause pain.
  
  
• Leg pain in children: Leg pain in children is a special situation. While most leg pain in children is not serious, there are times when the pain has a significant cause. These may include a joint infection causing hip pain, trauma causing damage to growth plates, and pain due to systemic illnesses like Henoch-Schonlein purpura, juvenile rheumatoid arthritis, or rheumatic fever.

"Growing pains" are most likely due to muscle overuse, although they may be associated with a mild stretching as the muscles grow along with bone.

• Diabetes: Diabetes may cause leg pain in a variety of ways. If blood sugar levels are not well controlled over a period of many years, nerves and blood vessels deteriorate and lose their function. Often the damage occurs in the feet. With loss of sensation, skin infections and foot injuries may occur without the patient feeling much discomfort. Alternatively, the nerves may be so inflamed that the patient feels intractable pain. Diabetes also causes blood vessels to narrow and cause symptoms of peripheral artery disease, or claudication.
  
  

Patients with diabetes are also more prone to infection because of an impaired immune system, and with poor blood supply to the legs, the skin integrity may be compromised, increasing the risk of foot and leg infections.