What Causes It?
Sudden directional changes - Rapidly changing direction while running can place excessive stress on knee ligaments, particularly the ACL.
Direct impact - A blow to the knee, such as during contact sports or a car accident, can damage any of the knee ligaments, with MCL injuries being particularly common from side impacts.
Landing incorrectly from a jump - Coming down from a jump with improper alignment can stress and tear ligaments, especially the ACL.
Stopping suddenly - Rapidly decelerating while running can cause the lower leg to stop while the upper leg continues forward, stressing the ACL or PCL.
Hyperextension - Forcing the knee to straighten beyond its normal range can damage the ACL or PCL.
Pivoting with planted foot - Rotating the knee while the foot is firmly planted on the ground can twist and tear ligaments, especially the ACL.
Repeat stress - Chronic strain on ligaments from certain sports or activities can weaken them over time, making them more susceptible to injury.
Previous knee injury - Having had a prior knee injury increases the risk of subsequent ligament damage.
Anatomical factors - Certain physical characteristics like wider pelvis, narrow intercondylar notch, or muscle imbalances can increase susceptibility to ligament injuries.
Poor conditioning - Inadequate strength and flexibility in muscles supporting the knee can increase ligament stress during activities.
Signs & Symptoms
Audible "pop" sound at the time of injury - Many people report hearing or feeling a popping sensation when a ligament tears, particularly with ACL injuries.
Immediate pain - Usually ranges from moderate to severe, depending on the extent of the injury and which ligament is affected.
Rapid swelling - The knee typically swells within minutes to hours after injury due to bleeding within the joint.
Limited mobility - Difficulty bending or straightening the knee and pain with movement.
Instability - Feeling that the knee "gives way" or buckles when trying to stand or walk, especially with ACL or PCL tears.
Tenderness along the joint line - Pain when pressing along the affected ligament.
Bruising - May develop around the knee within 24-48 hours after injury.
Inability to bear weight - Difficulty or inability to put weight on the affected leg.
Range of motion loss - Restricted movement due to pain, swelling, or mechanical blocking.
Sensation of the knee "locking" or "catching" - Particularly if there is associated meniscal damage.
Numbness or tingling - In some cases, if nerves are affected.