Stiff legs can be caused by exercise, a lack of activity, circulatory problems, injury and immune system reactions and many different diseases. In most cases, it isn’t serious. The fact so many different things cause the problem, however, means that being evaluated by a doctor is usually a good idea when it persists, gets worse or shows up with other symptoms.
Working out or doing sports is perhaps the most common cause for stiff legs, as too much activity can cause both cramps and delayed onset muscle soreness, or DOMS. Doctors and scientists aren’t sure exactly why cramps happen with exercise, but they think that it could be related to overstimulation of nerves, poor electrolyte balance and dehydration. Drinking electrolyte drinks and properly resting between exercise sets might help. DOMS, which usually is most noticeable the day after a workout, happens because microscopic tears form in the muscle. The body eventually repairs these tears and makes the tissue stronger.
Lack of Activity
Just as too much activity can be a bad thing for the legs, doing nothing isn’t a good idea, either. In some cases, a lack of movement can cause fluids in the body to build up in the legs, which can make them stiff and painful to shift. Additionally, activity “warms up” the tissue, making it more flexible. When a person doesn’t do anything physical for a while, the muscles get “cold” and shorten a bit, becoming more rigid. This is why people gain a greater range of motion as they exercise, and why they can be stiff in the morning or after sitting for a long time.
The simple solution for this problem is to get up and do some basic movements to gently warm up. Ones to try are squats, hamstring curls, toe taps with leg lifts and quadricep extensions. It is a good idea to do more than one set of these, gradually working toward a greater range of motion with each set.
In order to function well, muscles need enough oxygen. Blood carries the oxygen that is necessary to the working tissue, so when blood supply is limited, the muscle easily is fatigued and has a hard time moving. This can occur because of other medical issues such as diabetes, but it also can be the result of simply sitting in one position too long.
Injury and Immune System Reactions
Injury can result in stiff legs. This is typically because the immune system responds to the injury with inflammation, which helps the body repair damage and fight off infection. In order for this to happen, smooth muscles around blood vessels in the injured area have to contract to some degree. Without this process happening, leukocytes, or white blood cells that defend the body, would have a much harder time getting into the hurt tissue. When it happens right in the muscles, it is called myositis.
Inflammation and stiffness in the legs or other areas of the body is also linked to certain medical conditions. When a person’s diet is high in sugar or carbohydrates, for example, too much insulin can be released, which can trigger an immune system response. The problem also happens because of bacterial or viral infections and high amounts of certain hormones such as cortisol.
A number of diseases can cause stiff legs. These can be grouped very broadly into autoimmune, metabolic, and nervous system disorders. Many of these are thought to have genetic links, with research about treatments and cures still ongoing. The severity of symptoms often worsens over time as the conditions progress.
Probably the most well-known autoimmune condition that connects to leg stiffness is arthritis. This disease affects the joints, so it’s often the culprit when the lack of mobility is in the knee, ankle or hip. It is much more common in older people, but some types of arthritis appear even in teens and young adults. Over-the-counter anti-inflammatory medications often help, as do gentle activities such as swimming or walking.
Multiple sclerosis is an autoimmune disease that affects muscles. It attacks the nervous system, especially the brain and spinal cord, breaking down the fatty covering or myelin sheath around nerve cells. This disrupts nerve signals and can affect movement.
Andrenoleukodystrophy refers to a group of metabolic disorders that affect how the body metabolizes or breaks down fats. One of these, adrenomyeloneuropathy, is an inherited disease that, like MS, destroys the myelin sheath. This negatively affects physical functions and can lead to stiffness of the limbs.
Three other conditions might cause leg issues due to their connection to the nervous system. In syringomyelia, cysts form on the spinal cord. In nerve sheath neoplasm, tumors grow around the myelin sheath, especially in the spinal cord. Hereditary spastic paraplegia, which is a term actually covering several similar conditions, causes degeneration in the tract that connects the spinal cord and brain.
By itself, a single instance of leg stiffness generally is nothing to worry about. When it becomes progressively worse or happens with greater frequency, however, then a person should see a doctor. It is also a good idea to get a medical examination if the problem is present with other symptoms such as fever or seizures, as this might show that the cause is more severe.