What causes a leg muscle strain?

A muscle strain usually results when it is overly stretched, and the muscle fibers tear. Strains often happen near places where muscles connect to tendons.
Once you have strained a muscle, it may be prone to reinjury. This is true of leg strains. Proper healing is important, and preventative measures should be followed to prevent a leg strain from happening again.
Stretching or tearing of muscle fibers is known as a muscle strain. Strains usually occur for one of two reasons:
- The muscle was stretched beyond its limitations
- The muscle was forced to contract too far
The thigh has three large muscle sets — hamstrings, quadriceps, and the adductor muscles. The quadriceps and hamstrings are at high risk for muscle strains. This is because they cross both the knee joint and the hip joint. They are also used in activities that are high speed like running and soccer.
In minor strains, only a few muscle fibers are affected and the muscle remains strong. In major strains, the muscle may be torn, and you may not be able to properly use your leg. There are three grades to a muscle strain:
- Grade I — mild. Few muscle fibers are affected. There is tenderness but muscle strength remains.
- Grade II — moderate. More muscle fibers are affected. There is more pain and tenderness, along with mild swelling and some loss of strength
- Grade III — severe. The muscle is torn all the way through. There may be a "pop" sensation as the muscle sheds from tendon, a loss of muscle function, pain, discoloration, and swelling, and a possible dent under the skin
How long does it take for a leg muscle strain to heal?
Once your leg muscle is strained, time and rest are needed to allow the muscle to heal. A mild or grade I strain may need ten days to three weeks to heal. A severe strain to the hamstrings may take up to six months.
The healing outlook depends on the location and the severity of the muscle strain. In general, mild leg strains heal within weeks — major strains months, with surgical intervention if necessary.
Who can get leg muscle strain?
There are many factors that can put you at risk for muscle strain. These include:
- Muscle fatigue
- Muscle tightness
- Poor conditioning
- Muscle imbalance
Participating in contact sports like football and hockey can also increase your risk of getting a muscle strain. Participating in certain sports puts some sets of body muscles more at risk for strains. Quick start and jumping sports like basketball can cause leg strains.
What are the symptoms of a leg muscle strain?
Common symptoms of a leg muscle strain include:
- Abrupt severe pain
- Snap or pop sensation when the muscle tears
- Injured area painful to touch
- Visible bruising
Depending on the severity, symptoms may also include :
- Redness
- Muscle spasms
- Limited motion
- Muscle weakness
How is a leg muscle strain diagnosed?
Your doctor will conduct a physical exam and take a medical history to see how you obtained your injury. They may also ask if a pop was heard during the injury. They will also look for difficulty walking and a decrease in muscle strength.
Minor strains may not require more testing. If a major injury is suspected, X-rays or an MRI may be ordered. If the injury is in your calf, your doctor may want an ultrasound done to make sure you don’t have a blood clot.
How do you treat leg muscle strain?
Treatment for leg muscle strains varies depending on severity. First-line treatment includes RICE:
- Rest — getting away from the activity that caused your injury
- Ice — use of cold packs for swelling
- Compression — lightly wrapping the injured area to prevent additional swelling
- Elevation — propping your leg up above your heart level to minimize swelling
Your doctor may advise you to take medicines such as non-steroidal anti-inflammatories. As you get better, physical therapy may be added to your treatment. This will build stability and strength in the injured part of your leg. In cases of severe strains, surgery may be indicated.
Overall, the outlook for a mild sprain is good. Routine stretching and strengthening exercises at your fitness level help to decrease your risk for leg muscle strains.

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Drugs.com: "Leg Strain Guide: Causes, Symptoms and Treatment Options."
Harvard Health Publishing: "Muscle Strain."
Illinois Bone and Joint Institute: "Thigh Muscle Strains: Symptoms, Treatment and Prevention."
Mayo Clinic: "Muscle Strains."
OrthoInfo: "Muscle Strains in the Thigh."
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