Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
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 sciatica, or pain that radiates down the leg following the path of one of the many roots that make up the sciatic nerve. Overuse injuries may cause pain and can be thought of as multiple minor traumatic injuries that occur over a longer time span.
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 fibrous tissue lining of the bone, called the
periosteum
(peri=surrounding +osteum=bone). As well, the muscles surrounding the bone go
into spasm and intensify the pain.
Shin splints can be thought of as an overuse injury to the tibia or shinbone. This condition is also known as tibial stress syndrome. Running, jumping, and dancing are the most common causes.
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
a significant amount of pain as the pressure increases. Blood is also very irritating to the surrounding tissues when it leaves blood vessels.
Compartment syndrome describes the situation in which excessive swelling within the sections, or compartments, that contain muscles can cause increased pressure to the point that blood supply is cut off. Pain, numbness, and an inability to move the foot or ankle may be signs of compartment syndrome. This is a true surgical emergency, requiring opening of the compartments and relieving the pressure within to restore blood supply and prevent permanent disability.
Nontraumatic Leg Pain
There are numerous causes of nontraumatic 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, for example, gout (a
defect in the body's ability to process uric acid)
often attacks only one joint during an acute flare.
Peripheral artery disease (PAD): Pain in one leg, or both, 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 on 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
ache. 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, although the pain may be of different severity in each leg. 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. As well, poor blood supply makes it difficult for wounds like lacerations or abrasions to heal.
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 any 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.
Blood clots can also obstruct veins, causing pain. 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. Calf pain and swelling are common symptoms.
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 unless the clot develops near the groin where the two systems come together. Superficial veins can also chronically dilate and swell and form 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 third and fourth 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. There are some illnesses that cause leg weakness that may be associated with complaints of leg pain, including
Guillain-Barré syndrome and multiple sclerosis.
Skin: Skin inflammation may also cause significant pain, especially if there are underlying illnesses like diabetes or peripheral artery disease that prevent adequate healing. The inflammation may be due to infection often caused by
Streptococcus or Staphylococcus bacteria. Shingles
describes an inflammation of a nerve root that can cause significant pain in the leg and is due to reactivation of the chickenpox (varicella) virus. Skin that is stretched due to edema or fluid accumulation in the tissues underneath the skin can cause significant pain especially when the legs are not elevated.
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, knee, wrist, and fingers 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. The knee is often affected by pseudogout, and the diagnosis is sometimes made when calcification of the cartilage is seen on plain
X-rays of the knee joint.
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 anticoagulation (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.
Muscles will also go into spasm to help protect an injured site. For example, when a hip bone is broken, the muscles that move the hip will go into spasm to help minimize movement of the injury.
Muscle injuries: The muscles in the leg tend to act 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
affected person 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 PAD (peripheral artery disease) or claudication.
People 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 and the inability to easily heal cuts and abrasions.
