Diagnosing Knee Sprains & Strains

Doctors at NYU Langone Orthopedic Center use their expertise to diagnose knee sprains and strains.

A knee sprain occurs when some of the fibers in one of the ligaments surrounding or in the joint overstretch or tear. Ligaments are tough cords of tissue that connect and support bones and help to keep the knee stable while bending and rotating. A ligament sprain can be caused by a sudden impact, such as a collision during sports, or from putting too much weight or pressure on the knee, such as during weightlifting, or from landing awkwardly after a jump. A sudden twist or another movement that stretches the ligament too far can also cause a knee sprain.

A knee strain is a pull or tear that occurs in muscle fibers or in the tendons, which are fibrous cords of tissue that attach muscle to bone. Muscles and tendons help to move the bones that make up the knee joint. A strain may occur after a dramatic increase in activity. For example, many visitors to New York City develop muscle strains in their knees from walking more than they might at home.

Symptoms of knee sprains and strains can include pain, bruising, swelling, difficulty moving the joint, or a feeling of instability.

Medical History and Physical Examination

Your doctor may ask specific questions about your activities, symptoms, and prior injuries, and want to know whether your symptoms appeared immediately after an injury or in the days afterward. This helps your doctor determine if pain is a sign of osteoarthritis or other problem of the knee.

Your doctor may ask you to stand and walk to assess whether an injury affects your gait or causes a limp. You may need to bend and straighten your leg while you sit on the exam table for an evaluation of the range of motion in the knee.

During a physical exam, your doctor can often determine which type of knee injury you have. Imaging tests may be needed to confirm the diagnosis and to distinguish between other knee injuries.

Imaging Tests

Your doctor may recommend an X-ray to rule out another cause of the pain, such as a broken bone, arthritis, or bone spurs, which are small bony knobs that can form in joints when the ends of bones rub together. An X-ray may also show whether fluid has accumulated around a joint, which is a sign of a sprain or strain.

Our doctors often use ultrasound to diagnose muscle, tendon, and ligament injuries because the imaging test can produce clearer picture of soft tissues.

Doctors use MRI scan to examine the ligaments to determine the extent of a knee injury. The results of these scans can also determine if more than one structure in the knee is affected. For example, your symptoms may be caused by a knee cartilage injury, or a meniscus tear.

An MRI can also help your doctor determine whether a knee sprain is severe, meaning the ligament has partially or fully torn, typically requiring more extensive treatment, including possibly surgery. The most common ligament to tear is the anterior cruciate ligament (ACL).

If you have the symptoms of a sprain or strain, but the muscles, tendons, and ligaments of the knee seem healthy, your doctor may suspect another injury, such as a fracture. A CT scan or MRI can also help your doctor to find very subtle fractures that might otherwise go undetected.