Aching legs are commonly experienced by the elderly but can affect people of any age. It is also associated with a lot of medical conditions that’s why it is important to point your finger to the real cause of it, in order to know how to alleviate the pain.
A good history taken by your doctor will always be the starting point. After your doctor got the necessary information needed, assessment will then follow.
- Has there been a recent trauma or injury to the leg? Or did the pain suddenly come?
- Does it affect one or both legs?
- What aggravates the pain?
- Is it localized to the knee or the ankle? Or there are other symptoms associated with it like back pain?
- Does it hinder you from doing your daily activity? Does it keeps you awake at night?
- Have there been any physical changes on your legs (change in color, size, sensation, etc.)?
- How about the person’s general health and well being?
In some cases though, if the doctor is in doubt of the diagnosis, additional tests might be required. 
Aching Muscles when Lying Down
Experiencing leg pain at the end of the day after strenuous activities is expected. But experiencing pain at rest especially when lying down is another thing. 
It is primarily caused by atherosclerosis, a progressive hardening and narrowing of the arteries secondary to fat deposition which reduces the volume of the blood flow through them. Impeded blood flow results to a painful sensation. 
Signs / Symptom
Leg pain when lying down.
Picture 1: Atherosclerosis
Plaque deposition on the arteries may block the blood flow thus hindering sufficient blood flow to the feet and toes.
Image source : www.webmd.com
There is no treatment available for this type of leg pain but the following may be helpful to alleviate the pain: 
- Doing simple stretching of the calves during the day and whenever there’s an occurrence of pain.
- Application of warm or cold compress to help relax the muscles.
- Pain relievers.
But if the pain is recurrent and doesn’t just go away, a professional advice from your doctor is necessary.
Diet modification may be the key. Cut down the intake of saturated fats to prevent atherosclerosis in the future.
Fibromyalgia / Fibromyalgia Syndrome (FMS)
Fibromyalgia or FMS (formerly known as fibrositis) is a disorder characterized by widespread musculoskeletal pain that is not caused by tissue inflammation. It predominantly affects women ages 35-55 years old. It can occur independently or may be associated with another disease such as systemic lupus erythematosus or rheumatoid arthritis.
Currently unknown but scientists noted that there seems to be diffused disturbances of pain perception in patients with this condition.
Signs / Symptoms
- The cardinal sign of FMS is having “tender points” (localized areas of the body that are tender when lightly touched) that are found around the back of head, shoulders, sides of the breastbone, elbows, hips, and the knees.
- Numbness or tingling of different parts of the body
- Abdominal pain
- An irritable bladder 
Figure 2: Fibromyalgia Tender Points
Reporting 11 positive tender points out of 18 will affirm the diagnosis of Fibromyalgia.
There are no blood tests that can be done to diagnose FMS, but blood tests are important to exclude other medical conditions.
While there is no cure for FMS, the following are beneficial to manage the symptoms:
- Medications (tricyclic antidepressants, local injection of analgesic and/or cortisone medications).
- Acupuncture and massage therapy are also reported to be beneficial to some.
- Regular low impact exercise.
- Avoidance of alcohol and caffeine.
- Stress reduction .
- Sports or any rigorous activity
- Aging (age related wear and tear of the muscles).
- Diseases or disorders that affect multiple body systems or area like diabetes or peripheral artery disease (PAD). 
- Thigh pain may also be caused by life-threatening conditions like bone fracture, deep vein thrombosis, or hip dislocation. Seek immediate medical care when this happens.
Signs & Symptoms
- Presents as a pain, numbness or burning sensation that is felt between the pelves stretching down to the knees that could be located at your hamstring muscles, quadriceps muscles, and even radiate to your groin or buttocks area usually occurring on only one side of the body.
- The spine contains the sciatica nerves. When these nerves are compressed, there will be a pain on the back that radiates down the thighs.
Picture 4 : Sciatica
image source : virginiaspinecarechiropractic.com
Thigh pain caused by minor muscle strain may be controlled by home treatments like:
- Rest to immobilize the affected part and to prevent further injury to the muscle.
- Ice reduces swelling by vasoconstriction and is most effective if applied at 20 minutes interval within the day.
- Hot compress can be applied to promote blood flow and provide healing once the swelling subsided.
- Pain relievers could also be prescribed depending on the doctor’s discretion.
Stretching before doing rigorous activities like sports.
The knee joint which is made up of bone, cartilage, ligaments, and fluid plays an important role in our day to day activities. Muscles and tendons help the knee joint move so when any of these structures is hurt or diseased, you are greatly affected.
It is noted that bursitis, rheumatoid arthritis and osteoarthritis are some of the common diseases that may.
Bursitis is an inflammation that affects the bursa which is a fluid filled sac that cushions the joints. It affects shoulders, elbows, hips, knees and great toe.
- Repetitive motion.
Signs & Symptoms
Pain at the knee joint that presents gradually or suddenly.
- The bursitis usually diminishes on its own once the repetitive motion ceases.
- Rest, ice, elevation of the affected part.
- Anti-inflammatory drugs and pain medication.
- Antibiotic therapy for bursitis caused by infection.
- Surgical intervention (bursectomy) in some cases where the infection isn’t responsive to antibiotic therapy.
- Resting hours especially for person whose job is repetitive motion in nature.
- Exercise with gradual repetition.
2. Rheumatoid arthritis
Rheumatoid arthritis is an autoimmune disease that attacks people of all ages especially the women. It causes chronic inflammation of the joints. Early treatment of rheumatoid arthritis yields better outcome.
- Some say it might be genetically-linked.
Signs & Symptoms
- Pain that starts at the small joints of the hands, wrists and toes then later on moves to bigger joints of shoulders and knees.
- There may be stiff, tender, or painful joints typically in the early morning while others may report accompaniment of fatigue, weight loss or fever.
There is no known cure for rheumatoid arthritis. But treatment for it focuses on lessening the joint pain and prevention of further damage. It involves combination of patient education, rest, exercise, medications and occasionally, surgery.
Osteoarthritis on the other hand is the most common form of arthritis.
It causes inflammation of any joints, but with usual affectation on the cause aching in the knee. 
hands, knees, and spine. The pain is caused by the breakdown of the cartilage (the slippery tissue that covers the bones). Over time, when the cartilage breaks down, the bones will rub together and will make a permanent damage.
Treatment includes exercise, diet modification, medications and sometimes surgery. 
Risk factors for osteoarthritis include but are not limited to: old age, injury to the joint, or being overweight.
Confusion over the diagnosis between osteoarthritis and rheumatoid arthritis may occur. That’s why no single test can diagnose it.
A thorough medical history, physical examination, x-ray and blood tests are used.
Figure 3 Common Types of Arthritis
This is a visual representation of the difference between a
healthy joint, osteoarthritis and rheumatoid arthritis.
Aching Legs at Night / Restless Leg Syndrome (RLS)
- Imbalance in a chemical that transmits signals between nerve cells in the brain called dopamine.
- Genetic in nature because more than half of the population who suffer from RLS share the same condition with a family member.
- Pregnancy or old age.
- Triggered by health conditions like rheumatoid arthritis, diabetes, kidney failure, and iron deficiency.
It is the crawling, tingling or itching feeling in your legs that usually starts mild in the day then gets worse by night especially when you lie down and about to sleep and temporarily get better when you move, stretch or massage your legs.
Treating the underlying health conditions will help to eliminate the aches.
- Lifestyle modification (Stopping from smoking and drinking of alcoholic beverages).
- Cutting back the caffeine intake.
- Shedding off some extra pounds.
- Exercising in moderation. 
Aching Legs during Pregnancy
A collection of pain and aches will be experienced by a woman in the whole course of her pregnancy. One of which and the most common is the aching legs especially when the pregnancy is on its second to third trimester (most commonly on the third trimester). 
No one really knows why the pregnant woman gets more leg cramps than the other. It could be probably due to the extra weight that the legs are carrying all day or can be aggravated by the pressure that the growing uterus puts against the blood vessels that return blood back to the heart and on the nerves from trunk to the legs.
Signs & Symptoms
Like any other leg pain, this is a needle-like sensation that can be felt during the day but most noticeable at night.
- Avoid long standing or long sitting with crossed legs.
- Walk regularly, as long as there’s approval from the doctor.
- Have a warm bath and simple stretching of calf muscles before bedtime. 
- Lie on one side when sleeping to improve blood flow.
- Some experts also say that taking supplements like magnesium and calcium in adjunct to vitamins can help lessen the occurrence of it. But before taking any of these medications, make sure to consult your doctor and ask for advice.
Hence, if the leg pain is constant and there are physical changes such as swelling, redness and warmth at the area of concern, the doctor must be informed at once. This might be a clot that needs an immediate medical attention. 
Leg Aches during Flu
The flu, also known as influenza, is usually confused with the common colds.  But unlike the common colds that lasts only for a few days and with symptoms that are always above the neck, flu can have much more serious effects making you feel sick all over.
It is caused by a single family of viruses (the influenza viruses). Flu is contracted by coming into contact with the virus through touching an infected area (e.g. door handles, tables, etc.) or being around a person infected by the flu that coughs or sneezes.
Signs and Symptoms
Some common symptoms are high fever, hoarse cough, sore throat, headache and aching muscles (from back, arms and legs).
When you have flu, your whole body is aching most especially the legs because a large portion of your body’s resources and energy are being used to focus on rebuilding your immune system and fighting off the ailment. By this, a little is left over to power your muscles making it really painful.
Unfortunately, there are no treatments that can take away the flu and all its symptoms. Once the flu virus invades your system, you need to go through its course which usually lasts for a week or two. But the following methods can be tried to ease the pain:
- Hot bath to relax your muscles. 
- Having a massage is also helpful especially on the legs because this is mostly the cause of bother. Applying camphor while massaging the legs will provide additional soothing effect due to its warmth.
- Flu medications like Tylenol, aspirin and Advil are also helpful. Just make sure not to overmedicate because it may backfire and will make the situation even worse.
- But if you are experiencing dehydration, dizziness, high grade fever, difficulty of breathing and excessive sweating in a day or two, an immediate consultation with a physician will be needed.
Washing your hands regularly and keeping yourself away from person with flu will save you.