Ligament injuries account for 40 percent of injuries to the knee, and strains or tears of the medial collateral ligament (MCL) are the most common.1,2 A person who experiences an MCL injury typically reports a combination of the following symptoms:
- A “popping” sound when the injury occurs. This sound is usually a sign of a grade II or grade III tear.
- Immediate sharp pain from the inner section of the knee.
- Immediate swelling at the inner knee. Swelling may increase and spread to the actual knee joint 1 or 2 days following injury.
- Tenderness around the inner knee. This area may be painful to the touch.
- Increased pain a few hours after the injury.
- Bruising around the knee, especially around the location of the MCL (inner knee).
- Noticeable looseness in the knee. A person may be able to feel looseness around the inner knee when walking. The knee may feel as if it has a greater range of motion than normal.
- Knee stiffness may make walking, sitting down, rising from a chair or climbing stairs difficult. A person may have trouble bending or straightening the knee.
- Feeling of knee instability may be particularly noticeable during activities that strain the knee, such as going down stairs or pivoting on one leg. The knee may feel as if it is about to give out. Instability is usually associated with more severe MCL tears.
- Pain when bearing weight, such as when walking, sitting down, or rising from a chair.
While some symptoms occur immediately after injuring the MCL, such as swelling and tenderness, others may appear or get worse in the days following the injury, such as bruising.
MCL injuries are acute and therefore typically not related to progressive knee conditions, such as osteoarthritis. Most people are able to pinpoint when and how the injury occurred.
Most MCL sprains and tears heal within a short time, ranging from a few days to a few months. A small group of people may experience a chronic MCL injury, which means that the symptoms persist for 3 months or more following treatment.
People with MCL injuries may also present with damage to other structures in the knee, such as the anterior cruciate ligament (ACL) or meniscus. These other injuries may cause additional symptoms, such as difficulty straightening the knee.