A sprained knee occurs when the ligaments in the knee are stretched or torn. These strong bands of tissue connect bones, providing stability to the knee joint. The injury can range from a mild stretch to a complete tear, affecting knee function.
What Exactly is a Sprained Knee?
A sprained knee involves damage to the ligaments, which are rope-like structures that link the thigh bone (femur) to the shin bone (tibia) and other bones in the lower leg. These ligaments ensure the knee moves correctly and remains stable. When forced beyond their normal range of motion, they can stretch or tear.
The knee contains four main ligaments often involved in sprains. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) cross inside the knee, controlling its forward and backward motion. On the sides, the medial collateral ligament (MCL) runs along the inner knee, and the lateral collateral ligament (LCL) is on the outer knee, both providing stability against sideways forces.
Recognizing the Symptoms
Immediate signs of a sprained knee include pain, often felt around the affected area and potentially worsening with movement or when bearing weight. Swelling typically develops in and around the knee.
Other indicators include tenderness to the touch and bruising. The knee might feel unstable, or as though it could “give out” or buckle, especially when trying to stand or walk. A popping or snapping sensation might be heard or felt at the time of injury, particularly with more severe sprains.
Causes and Grades of Sprains
Knee sprains often happen due to movements that force the knee beyond its natural range. Common causes include sudden twists, direct impacts to the knee, hyperextension, or awkward landings, which frequently occur during sports activities or falls. For instance, a blow to the side of the knee can injure the MCL, while a sudden twist or jump can affect the ACL.
Knee sprains are classified into three grades based on ligament damage. A Grade 1 sprain is mild, involving slight stretching or minimal tearing of ligament fibers without significant instability. Individuals may experience mild pain, swelling, or bruising, but can generally still put weight on the leg.
A Grade 2 sprain indicates a moderate injury where the ligament is partially torn, leading to increased looseness and instability. This results in more noticeable pain, swelling, and difficulty bearing weight. A Grade 3 sprain involves a complete tear of the ligament, causing significant instability and often making it difficult or impossible to put weight on the affected leg.
First Aid and When to Seek Professional Care
Immediate first aid for a suspected knee sprain involves the R.I.C.E. protocol: Rest, Ice, Compression, and Elevation. Resting the injured knee by avoiding activities that cause pain helps prevent further damage and allows healing. Apply ice to the affected area for 15-20 minutes at a time, several times a day, to reduce pain and swelling. Wrap the knee with an elastic bandage for compression, ensuring it is snug but not overly tight to avoid restricting circulation. Elevate the injured leg above heart level, especially while resting, to minimize swelling.
While many mild sprains can improve with consistent home care, clear signs indicate a need for professional medical attention. If you are unable to bear weight on the injured leg, experience severe pain, notice significant swelling that worsens, or if the knee feels unstable and prone to “giving out,” consulting a healthcare provider is important. Other reasons to seek care include a deformed appearance of the knee, numbness, or if symptoms do not improve after a few days of self-care.
A doctor will likely perform a physical examination to assess the knee’s range of motion and stability, often comparing it to the uninjured knee. To confirm the diagnosis and rule out fractures, imaging tests may be ordered. X-rays can identify bone fractures, while magnetic resonance imaging (MRI) provides detailed images of soft tissues, including ligaments, to determine the sprain’s extent.