Originally published by Harvard Health.

What Is It?

A muscle strain is a stretch or tear of muscle fibers. In the leg, muscle strains happen when a muscle is either stretched beyond its limits or forced into extreme contraction. Because the leg has many different muscles, it is vulnerable to several different types of muscle strains. Some of the more common ones are:

• Calf muscle strain (gastrocnemius strain). The calf muscle typically gets strained when the foot suddenly bends upward, stretching the calf muscle beyond its limits. At the time of injury, you may hear or feel a pop inside your calf — the sound of the muscle tearing or shearing away from the Achilles tendon. Calf muscle strains are common in athletes, especially tennis players and joggers. However, they also can happen during a simple stroll, if your foot flexes upward when you step into a hole in the sidewalk or if your heel slips off the edge of a curb.
• Plantaris strain. The plantaris is a thin muscle that begins at the lower end of the femur (the large bone of the upper leg), stretches across the knee joint and attaches to the back of the heel along with the Achilles tendon. Because the plantaris doesn’t contribute much force in bending the knee, a tear in this muscle may not seriously affect your knee function. However, a severe plantaris strain can cause significant pain, usually at the back of your calf rather than near the knee. A plantaris strain can occur alone or accompany a gastrocnemius strain or a tear of the anterior cruciate ligament (ACL), a major, stabilizing ligament in the knee.
• Hamstring strain (pulled hamstring). Hamstrings are long muscles that extend down the back of the thigh. Because hamstrings work to pull back the leg and bend the knee, they can be injured during running, kicking or jumping. You may feel a pop, usually at the back of the thigh, when the muscle tears.
• Quadriceps strain. The quadriceps is a large group of muscles in the front of the thigh that straighten out the knee, the opposite action from the hamstrings. Quadriceps strain is a common injury in runners. However, it also may occur during a strenuous leg press at the gym. The pain of a quadriceps strain is felt in the front of the thigh. The strain may be described as a groin pull if the tear is fairly high in the muscle.

To help simplify diagnosis and treatment, doctors often classify muscle strains into three different grades, depending on the severity of muscle fiber damage.

• Grade I. Only a few muscle fibers are stretched or torn, so the muscle is mildly tender and painful, but muscle strength is normal.
• Grade II. A greater number of muscle fibers are torn, so there is more severe muscle pain and tenderness, together with mild swelling, noticeable loss of strength and sometimes bruising (called ecchymosis).
• Grade III. The muscle tears all the way through. Either it rips into two separate pieces or the fleshy part of the muscle breaks away from the tendon. Grade III muscle strains are serious injuries that cause complete loss of muscle function, as well as considerable pain, swelling, tenderness and discoloration. A Grade III strain also causes a break in the normal outline of the muscle, often producing an obvious dent or gap under the skin where the ripped pieces of muscle have come apart.

Symptoms

Symptoms of a strained leg muscle can include:

• Muscle pain and tenderness, especially after an activity that stretches or violently contracts the muscle. Pain usually increases when you move the muscle, but it is relieved by rest.
• Local muscle swelling, black and blue discoloration or both
• Either a decrease in muscle strength or (in a Grade III strain) a complete loss of muscle function
• Difficulty walking
• A pop in the muscle at the time of injury
• A gap, dent or other defect in the normal outline of the muscle (Grade III strain)

Diagnosis

Your doctor will want to know what activity triggered your leg pain and whether there was a pop in the muscle when you injured it. The doctor also will ask about your symptoms, especially any decreased muscle strength or difficulty walking.

To confirm a diagnosis, the doctor will examine you. If the results of your exam point to Grade I or II muscle strain, you probably will not need any additional testing. However, if the diagnosis is in doubt, X-rays or a magnetic resonance imaging scan may be necessary. Also, in calf muscle injuries, Doppler studies may be done to check for a blood clot.

Expected Duration

Most Grade I or Grade II strains begin to feel better within a few days. In most cases, symptoms are either totally gone, or very much improved, within 8 to 10 weeks. Symptoms of a Grade III strain may last until the torn muscle is repaired surgically.

Prevention

To help prevent muscle strains in your legs, you can:

• Warm up before you participate in high-risk sports.
• Follow an exercise program aimed at stretching and strengthening your leg muscles.
• Increase the intensity of your training program gradually. Never push yourself too hard, too soon.

Treatment

If you have a Grade I or Grade II strain, your doctor will probably recommend that you follow the RICE rule:

• Rest the injured muscle (take a temporary break from sports activities).
• Ice the injured area to reduce swelling.
• Compress the muscle with an elastic bandage.
• Elevate the injured leg.

In addition, you can take a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen (Advil, Motrin and other brand names) or aspirin, to ease pain and relieve swelling. As pain gradually subsides, your doctor may recommend a rehabilitation program to restore the normal range of motion in your leg and to gradually strengthen the injured muscle.

If you have a Grade II strain, you may need to be evaluated by a specialist, such as an orthopedist. To allow the injured muscle to heal, you may need to wear a cast for a number of weeks.

If you have a Grade III strain in your leg, the torn muscle may need to be repaired surgically by an orthopedic specialist. One exception is a Grade III plantaris strain, which usually is treated without surgery.

When To Call a Professional

Call your doctor promptly if:

• You hear or feel a pop in your leg muscle at the time of injury
• You have severe pain, swelling or discoloration in the injured muscle
• Your injured leg is obviously weak compared to your uninjured leg
• You have difficulty walking
• You have milder leg symptoms that do not improve after 48 hours

Prognosis

The outlook depends on the location and severity of the muscle strain. In general, almost all Grade I strains heal within a few weeks. Grade II strains may take two to three months. After surgery to repair a Grade III strain, most people regain normal leg muscle function after several months of rehabilitation.

Additional Info

National Institute of Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse
National Institutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
Phone: 301-495-4484
Toll-Free: 1-877-226-4267
Fax: 301-718-6366
TTY: 301-565-2966
http://www.niams.nih.gov/

National Institute for Occupational Safety and Health
395 E Street, S.W.
Suite 9200
Patriots Plaza Building
Washington, DC 20201
Toll-Free: 1-800-232-4636
TTY: 1-888-232-6348
http://www.cdc.gov/niosh/

National Rehabilitation Information Center (NARIC)
8201 Corporate Drive
Suite 600
Landover, MD 20785
Phone: 301-459-5900
Toll-Free: 1-800-346-2742
TTY: 301-459-5984
http://www.naric.com/

American Academy of Orthopaedic Surgeons (AAOS)
6300 North River Road
Rosemont, IL 60018-4262
Phone: 847-823-7186
Fax: 847-823-8125
http://orthoinfo.aaos.org/

National Athletic Trainers’ Association
2952 Stemmons Freeway
Dallas, TX 75247
Phone: 214-637-6282
Fax: 214-637-2206
http://www.nata.org/

American Physical Therapy Association
1111 North Fairfax St.
Alexandria, VA 22314-1488
Phone: 703-684-2782
Toll-Free: 1-800-999-2782
TTY: 703-683-6748
Fax: 703-684-7343
http://www.apta.org/