Knee strains are a common injury involving a torn muscle or tendon around the knee. Strains are often related to sports injuries.
According to a 2012 analysis, knee sprains and strains are the most common knee injuries seen in emergency rooms in the United States, accounting for 42.1% of cases.
This article explores the symptoms and possible causes of knee strains and sprains, along with available treatment options.
Knee strains affect the muscles or tendons.
The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) state that they occur when a tendon or muscle stretches or tears. A tendon is a structure in the body that connects muscles to a bone.
A muscle strain around the knee is often due to overuse. The NIAMS indicate that a person may strain their knee from stressing the muscles, lifting heavy weights, or a sudden injury.
There are three grades of muscle strain based on severity.
- Grade 1: A few muscle fibers are torn or stretched, and the muscle retains full strength.
- Grade 2: This involves more muscle fibers being stretched and torn. The muscle becomes weaker and is more painful.
- Grade 3: The most severe type of strain involving significant or complete tearing of the muscle or tendon, which causes loss of function.
There are several potential symptoms of a knee strain. According to the NIAMS, they commonly include:
- cramping in the muscles around the knee
- spasms in the muscles
- difficulty with moving the muscles or walking
The severity of symptoms will vary according to the severity of the strain.
While strains affect the muscles and tendons, sprains affect the ligaments.
The NIAMS define a sprain as an injury to one or more ligaments from a stretch or tear. Ligaments are tough connective tissues linking bones to other bones.
There are four major ligaments of the knee joint. Of these, the anterior cruciate ligament (ACL) experiences the most injuries. A person can injure their ACL through contact, such as a football tackle, or without contact, which commonly occurs due to a sudden twisting motion.
Although both cause pain and swelling, knee sprain symptoms also often include difficulty putting weight on the leg, alongside pain with range of motion.
The most common causes of knee strains include:
- twisting or lifting a heavy object without proper support
- recent injury to the knee or muscle
- overuse of the muscle
A tear to the tendons that run through the knee is a common sports injury.
According to the American Academy of Orthopaedic Surgeons (AAOS), two common tendon tears in the knee include a patellar tendon tear and a quadriceps tendon tear.
Common causes of tears to these tendons include:
- landing awkwardly
- direct force to the front of the knee
- misstepping and “jamming” the knee
Often, people can treat knee strains at home.
- Rest: May include using assistive walking devices to avoid moving or putting weight on the knee.
- Ice: Wrap ice with a towel and apply to the knee to help reduce swelling.
- Compression: This can involve using a wrap or specialized bandage to apply pressure to the knee.
- Elevation: This can help reduce swelling.
In addition to RICE, over-the-counter anti-inflammatory medications, such as acetaminophen or ibuprofen, may reduce pain and swelling.
It is always best to consult with a doctor if a person is unsure which medication to use, or if they take regular prescription medications.
Although people may need surgery for some knee injuries, a doctor may recommend several non-surgical treatments before discussing surgical options.
According to the AAOS, some common treatments may include:
- physical therapy
- immobilizing the knee with a brace
- using crutches
If the knee strain or sprain is severe, surgery may be necessary to restore stability and function.
Recovery time varies greatly from person to person, according to the severity of the injury and whether they underwent an operation.
The United Kingdom’s National Health Service (NHS) note that people experiencing strains will feel better after 2 weeks. However, more severe injuries can take significantly longer.
Following a knee strain or sprain, a person should avoid strenuous exercise, such as running and jumping, until symptoms improve significantly. This recommendation is to avoid the risk of further damage.
The AAOS note the following recovery times for a tendon tear:
- for mild cases, it can take 3–6 weeks to recover
- after surgery, it can take 6 months to a year for complete recovery
Although a person can treat most minor knee sprains and strains at home, the AAOS recommend seeking immediate medical attention for a knee injury if people experience any of the following:
- severe pain at the site
- hearing or feeling a popping noise or sensation at the time of injury
- inability to move the knee
- swelling at the injury site
A person should also seek medical attention if the pain or swelling gets worse, or if new symptoms develop. Always consult with a doctor if there is no improvement in symptoms following home treatment.
To diagnose a knee strain or sprain, a doctor will ask questions about a person’s symptoms, medical history, and if they participate in sport or similar activities.
They will then examine the knee and test for strength and range of motion, alongside other tests.
Healthcare professionals will usually obtain X-rays to check for broken bones. A doctor may also order an MRI to examine the tendons and ligaments of the knee.
Preventing a knee sprain or strain is not always possible, but there are ways to reduce the chances of sustaining injury.
The NIAMS recommend the following:
- eating a healthful diet
- maintaining a moderate weight
- wearing properly-fitted shoes
- avoiding exercising or playing sports when tired or in pain
- running on flat surfaces
- warming up and stretching before exercise
- taking part in regular exercise
- wearing protective equipment when playing sports
A knee strain occurs when a muscle or tendon stretches or tears. The severity of the strain can vary from mild to severe.
Mild cases often do not require medical attention, and a person can treat them at home.
More severe cases may require immobilization, physical therapy, or surgery. Recovery times can vary based on how severe the strain is and can range from several weeks to a year.