Magnetic resonance imaging offers doctors amazing ability to diagnose a wide variety of injuries. Use of MRI has become common in orthopedic surgery. You don’t need an MRI for every injury. There are many injuries, though, where MRIs can help doctors and orthopedic surgeons make the diagnosis.
Rotator cuff tear
The rotator cuff is a set of muscles that come off the shoulder blade. Their tendons attach to the humerus (the ball of the ball-and-socket joint). They help to stabilize the ball in the socket while the bigger muscles around the shoulder lift the arm overhead, out away from the body and behind the back. A doctor can examine your shoulder to detect weakness of the rotator cuff. After x-rays, the surgeon could get an MRI to show a tear of one or more of the rotator cuff tendons.
Rotator cuff tears
The labrum is a cartilage bumper that surrounds the socket of the shoulder. You can tear the labrum with traumatic events like shoulder dislocations. Repetitive overhead activity, like pitching in baseball, can also injure the labrum. A doctor might suspect a labral tear by certain physical exam tests. An MRI or MR arthrogram (MRI after the radiologist injects dye into the patient’s shoulder) can demonstrate a labral tear.
Anterior cruciate ligament (ACL)
The anterior cruciate ligament (ACL) is a ligament in the center of the knee that is important for knee stability. ACL tears are common in sports and other physical activities. The orthopedic surgeon can often detect laxity in the knee consistent with an ACL tear. Pain and swelling often make physical examination difficult. X-rays might show associated findings that suggest an ACL tear. MRI is highly sensitive for detecting ACL injuries.
Posterior cruciate ligament (PCL)
The posterior cruciate ligament (PCL) is located just behind the ACL. It is also important for knee stability. PCL tears are much less common ACL tears. They can occur in sports, falls, and motor vehicle accidents. MRIs can detect PCL tears and any associated injuries.
Medial collateral ligament (MCL)
The medial collateral ligament (MCL) is the ligament on the medial (side closest to the midline) side of the knee. The orthopedic surgeon can usually demonstrate an MCL injury by physical exam. An MRI can show where the MCL is injured. It can also show the severity of the injury and the presence of any associated injuries.
Meniscus tears are extremely common. Surgeries to treat them are among the most common surgeries in all of orthopedics. The meniscus is a C-shaped shock-absorbing piece of cartilage between the femur and tibia. There is one located on both the medial and lateral sides of each knee. An MRI can show meniscus tears. Degenerative meniscus tears often coexist with osteoarthritis. Therefore, the surgeon must carefully judge the cause of a patient’s pain. Surgery for a degenerative meniscus tear in the setting of arthritis might not help to relieve a patient’s pain.
Therefore, orthopedic surgeons often try to avoid getting an MRI or choosing surgery based solely on the presence of a meniscus tear on MRI in these situations.
It’s easy to detect a patella dislocation while the patella is out of place. Most patients, though, present after the injury has been reduced. X-rays are often normal. An MRI can detect articular cartilage damage or ligament injury that occurred during the dislocation.
MRI can demonstrate damage to the articular cartilage, the cartilage lining the end of the bones. Occasionally contrast injected into the knee can improve visualization of the cartilage.
Early in the course of the injury, x-rays often do not show a stress fracture. After several weeks, an x-ray can show healing of the bone. An MRI can show edema (fluid) within the bone and/or a small fracture line.
Tendons attach muscles to bones. In addition to rotator cuff tendons of the shoulder mentioned earlier, tendon injuries can occur around the knee, ankle, elbow and more. Orthopedic surgeons can often diagnose some tendon injuries, like Achilles, patellar and quadriceps tendon injuries without an MRI. Some injuries are more subtle. An MRI can help diagnose these injuries.
Injuries of the muscles, like the quadriceps and hamstring muscles of the thigh, are common in sports and exercise. Doctors often can make the diagnosis without an MRI. An MRI can help to show the severity and specific location of the muscle injury.
This list does not include every possible injury or reason to obtain an MRI, but these are some of the most common findings on MRI. When seeing an orthopedic surgeon for an injury, you can discuss whether or not an MRI would be helpful.