A sprained knee can make simple movements, like walking, standing, or climbing stairs, painful and frustrating. Whether it’s caused by sports, a fall, or sudden twisting, this common injury affects thousands each year. Understanding what causes a knee sprain, when to seek emergency care, how to recognize symptoms, and what recovery involves can help you heal faster and avoid long-term damage. Here’s everything you need to know about sprained knees.
What Is a Sprained Knee?
The knee is the largest and one of the most complex joints in the human body. It connects the thigh bone (femur) to the shin bone (tibia), with the kneecap (patella) protecting the front of the joint. Smaller bones like the fibula also play a role in stability. The knee’s movement is made possible by a network of ligaments, tendons, cartilage, and muscles that work together to support weight and allow motion like bending, straightening, and rotation.
Key Ligaments of the Knee
- Anterior Cruciate Ligament (ACL): Controls forward motion of the tibia and stabilizes rotational movement.
- Posterior Cruciate Ligament (PCL): Prevents the tibia from sliding backward under the femur.
- Medial Collateral Ligament (MCL): Provides inner knee stability and resists forces from the outer side.
- Lateral Collateral Ligament (LCL): Provides outer knee stability and resists forces from the inner side.
These ligaments act like strong ropes, keeping the bones properly aligned and ensuring smooth joint function.
Symptoms of a Sprained Knee
Recognizing the symptoms of a sprained knee early is important to prevent the injury from worsening and to start proper treatment quickly. Symptoms can appear immediately or develop over several hours, and their severity depends on how much the ligament is stretched or torn.
- Pain and tenderness: Ranging from mild aches to sharp discomfort, especially when bearing weight. Pain location can indicate which ligament is injured.
- Swelling and bruising: Fluid buildup and discoloration within hours of injury, often signaling internal bleeding and inflammation.
- Limited mobility: Difficulty bending or straightening the knee fully, making walking or climbing stairs challenging.
- Instability or popping sound: A “pop” heard during injury or a sensation of the knee “giving out,” common in moderate to severe sprains.
Causes of a Sprained Knee
A sprained knee can happen to anyone, from athletes to people performing everyday tasks, but certain movements and conditions raise the likelihood of injury. Understanding these causes can help you avoid situations that put excess strain on the knee ligaments.
Sudden twisting or awkward movements
Quick pivoting or sudden changes in direction are among the leading causes of knee sprains, especially during sports like basketball, soccer, and skiing. These activities require rapid knee rotation, which can overstretch the anterior cruciate ligament (ACL) or medial collateral ligament (MCL). A simple misstep or losing footing on uneven ground can also trigger a sprain.
Direct impact or trauma
A blow to the knee, whether from a sports collision, fall, or car accident, can force the joint into an unnatural position. This impact often damages the posterior cruciate ligament (PCL) or lateral collateral ligament (LCL), which provide stability on the outer and back sides of the knee. High-impact trauma can also injure multiple ligaments at once, resulting in a more severe sprain.
Overextension during activity
Pushing the knee past its natural range of motion, also known as hyperextension, puts excessive stress on the ligaments. This can occur while jumping, sprinting, or performing high-intensity drills without proper warm-up. Athletes and dancers are particularly prone to this type of injury because of the repeated strain on the joint.
Weak muscles or poor balance
Muscles around the knee, including the quadriceps and hamstrings, act as secondary stabilizers. When these muscles are weak or imbalanced, the ligaments bear more load and are more susceptible to injury. Poor balance or coordination, common in beginners or older adults, also makes sudden missteps more likely, increasing the risk of sprains during everyday activities like walking on uneven surfaces or climbing stairs.
How to Diagnose a Sprained Knee
Accurate diagnosis is essential to determine the severity of a sprained knee and choose the right treatment plan. Doctors evaluate the injury through physical examination and imaging tests to rule out fractures or other knee problems.
Diagnosis Process
- Physical examination: The doctor checks for swelling, bruising, tenderness, and range of motion. They may gently move the knee to assess ligament stability and pinpoint which ligaments are affected. Stress tests, such as the Lachman or valgus/varus stress test, are often used to evaluate ligament integrity.
- Medical history: Information about how the injury happened, previous knee injuries, and your activity level helps guide diagnosis.
Diagnostic Tests
- X-rays: Used to rule out bone fractures or dislocations that may mimic sprain symptoms.
- MRI (Magnetic Resonance Imaging): Provides a detailed view of soft tissues like ligaments, tendons, and cartilage to detect partial or complete tears.
- CT scan (Computed Tomography): Occasionally used for more complex injuries or when MRI results are inconclusive.
Grading the Severity of a Sprained Knee
- Grade I (Mild): Ligaments are slightly stretched; minimal pain, swelling, and no significant instability.
- Grade II (Moderate): Partial ligament tear; noticeable pain, swelling, and some difficulty bearing weight.
- Grade III (Severe): Complete ligament tear; severe swelling, instability, and inability to use the knee normally.
Treatment Options for a Sprained Knee
Treatment depends on the severity of the ligament injury. Mild sprains often heal with self-care, while moderate to severe sprains may require professional medical intervention or even surgery. The goal is to reduce pain and swelling, restore knee stability, and prevent future injuries.
At-Home Treatments (RICE Method)
The RICE method is the first line of treatment for most mild to moderate knee sprains:
- Rest: Avoid putting weight on the injured knee. Use crutches if necessary to prevent further damage.
- Ice: Apply an ice pack for 15–20 minutes every 2–3 hours during the first 48 hours to control swelling and pain.
- Compression: Wrap the knee with an elastic bandage or use a compression sleeve to minimize swelling and provide support.
- Elevation: Keep the knee elevated above heart level, especially while resting or sleeping, to promote fluid drainage and reduce inflammation.
Over-the-counter medications like ibuprofen or acetaminophen can also help relieve pain and reduce inflammation during the healing process.
Medical Treatments
If symptoms are severe or don’t improve with home care, medical treatments may be necessary:
- Physical therapy: Guided exercises to strengthen muscles around the knee, restore range of motion, and prevent future sprains.
- Knee braces or supports: Provide extra stability during recovery, especially for athletes or individuals returning to activity.
- Surgery: Required for severe ligament tears (e.g., ACL or combined ligament injuries) that cannot heal on their own. Surgical repair is often followed by an extensive rehabilitation program.
Get Immediate Care at STAT Specialty Hospital – Open 24/7
If your knee pain is severe, swelling continues to worsen, or you’re unsure whether it’s a sprain or something more serious, don’t delay seeking help. Immediate evaluation can prevent long-term damage and speed up recovery. STAT Specialty Hospital is open 24/7, providing expert emergency care, on-site imaging, and specialized treatment for knee injuries. Their experienced team ensures you get fast, accurate diagnosis and the right care plan to get back on your feet. Visit STAT Specialty Hospital anytime for peace of mind and quick relief.