The intense pain of the muscle in your calf knotting up is a leg cramp. Nocturnal leg cramps or leg cramps at night are a fairly common phenomenon and generally affect older persons as well as pregnant women. However, younger adults are also known to suffer from these pains. These cramps usually occur at night after sleep or during a wakeful period between phases of sleep. The muscles in your calf act involuntarily and it can last anywhere from a few seconds to few minutes. While most experience a reduction in the pain as soon as the cramp has subsided, many people are affected for more than 24 hours.

Why do these nocturnal leg cramps occur?
Leg cramps at night are not a serious medical disorder, in fact, doctors cannot often pinpoint why the leg cramps happen. Depending on the frequency of the leg cramps, you should visit your doctor to analyze the reason behind the leg cramps. They will know how to treat leg cramps which occur at night. 

Unknown causes
Idiopathic or unknown leg cramps are most common in individuals. There is no known reason and cramps simply occur due to a contraction of the muscle.

Known Causes
There are also secondary causes or reasons due to which the leg cramps occur. Some of the common ones are:

• Extreme exercise
  If a person is not used to exercise or if the exercise is more than the regular amount, then there is a higher chance of leg cramps. This affects even athletes a lot if they stretch their limit and play for too long. This is connected to the loss of salts and minerals due to sweat and wear and tear of the muscle.
• Alcoholism
  Alcohol is known to dehydrate the body severely and over a period of time, this starts affecting the muscles. Therefore, alcoholics often suffer from leg cramps.
• Pregnancy – Most pregnant women suffer from leg cramps during their third trimester. Generally, once the baby is born the cramp discontinues.
• Electrolyte imbalance
  This is a major disorder due to which leg cramps occur in normal people. Minerals and salts are an important element in maintaining the health of muscles. These are lost due to everyday activities like exercises, sweat etc. It can be a perennial problem for some hence, it is advisable to consult a doctor at the earliest.
• Medical conditions or diseases
  Leg cramps may be a symptom of more serious conditions like hypothyroidism, kidney failure, motor neuron problems, and peripheral artery diseases. There are also other conditions like allergies to certain medications that can cause leg cramps.

How do you treat or alleviate the leg cramps?
Leg cramps cause intense pain, however, there is no specific medication that can be taken to treat it. Only the underlying cause can be identified and treated accordingly. There are only measures that you can take to alleviate and prevent the pain.

While the leg is cramping, the pain is so intense, you can hardly do anything during that time. Yet, you can try these remedies to help with the pain. The pain will subside in a few minutes.

• Stretch muscles
  Try to stretch the muscles while holding it with your hand. You can get someone to help you out with this or stretch the muscles yourself.
• Keep a hot pack or soak in a hot bath
  You can apply a hot pack to relieve the tension in the calf muscles. Alternatively, you can have a hot water bath or soak a towel in hot water and apply to the area. A hot pack is the best option as you might not want to take a bath in the middle of your sleep schedule.
• Walk or jiggle the leg
  Try to walk and stretch the muscles. You can also shake or jiggle your leg to help move and stretch the muscles.

Do not take OTC painkillers as it will take a while for the painkillers to affect the body, by then the leg cramp will subside.

Preventing the leg cramps
The best way to know how to treat leg cramps is to prevent the pain itself. These are some of the things you can do to prevent the pain.

• Walk and stretch before bed
  Engage in light stretching exercises or a short walk to loosen the muscles prior to bedtime. This will relieve the tension of the muscles.
• Stay hydrated
  Hydrate yourself with 6-8 glasses of water through the day. You can know if you are hydrated by looking at the color of your urine. It needs to be clear instead of shades of yellow.
• Follow a comfortable sleeping routine
  Leg cramps at night are very common. Make sure you keep the blankets loose around yourself. Sleep with pillows propped up at the end of your bed so that your feet are pointing upwards. This will not create your legs to contract while you sleep.

Maintain a diary and note the frequency and symptoms of cramps if you experience cramps regularly. This will help your GP or doctor to give you the best medication.