Any injury to the ligament is called a sprain. A ligament is a fibrous tissue that joins bones together, providing stability and support.
The knee’s many ligaments are divided into two categories: the cruciate ligaments and the collateral ligaments.
- The cruciate ligaments, which form the “X” structure in the middle of the knee joint, are the ACL (anterior cruciate ligament) and the PCL (posterior cruciate ligament). The ACL prevents the bone of the lower leg from slipping forward on the thigh bone, and the PCL prevents excessive backward movement of the lower leg.
- The collateral ligaments are found on the sides of the knee and are responsible for preventing unnecessary side-to-side movements. These are the MCL (medial collateral ligament), located at the inner side of the knee, and the LCL (lateral collateral ligament), located at the outer side. The MCL limits excessive inward movement of the lower leg, while the LCL prevents excessive outward movement.
How Do I Know if I Sprained My Knee?
A knee sprain will feel different for each individual, and the symptoms that you will experience will depend on the type of ligament affected.
- If the ACL is damaged, a popping or cracking sound may be felt or heard at the time of injury, and there will be an immediate feeling of the knee giving out; if the PCL is affected, there will be pain on the back of the knee and kneeling might be difficult.
- If the MCL is injured, a popping sound may be heard or felt, and there will be immediate pain and swelling on the inner side of the knee; if the LCL is affected, pain, tenderness, and swelling are observable on the outer side of the knee, and the knee might lock or feel stuck.
Types of Knee Sprains
A sprain in any of the ligaments is graded based on the following:
- Grade 1 or Mild
- The ligament stretches, and the only visible damage is microtears. The knee is still stable and can support the body.
- Grade 2 or Moderate
- The ligament partially or incompletely tears. There is some instability in the knee, and the knee might feel like it will give out.
- Grade 3 or Severe
- The ligament tears completely. The knee is unstable, and putting weight on the affected leg is difficult.
What Does a Knee Tear Feel Like?
Another important structure in the knee joint, aside from the ligaments, is the meniscus. There are two menisci in the knee: the medial and lateral menisci.
The menisci are crescent-shaped cartilages situated between the joints. They cushion the knee and protect it from stress endured through walking, running, climbing and jumping.
A knee tear can happen in any of the ligaments or menisci. The ligaments or menisci may rip apart separate from their bony attachments. The damage may be partial or complete, or it might entirely separate from the bone. In severe cases, it can result in an avulsion fracture wherein the ligament pulls off a part of the bone when it tears.
If you have a torn ligament or meniscus, you may feel pain immediately after the injury. There will also be swelling and bruising on your knee. A severe tear may feel like your knee is buckling. It might not be able to tolerate weight-bearing, and the knee might be difficult to bend and straighten. The knee might also look deformed and misaligned.
Damage to an isolated knee structure is rare. Most knee injuries involve several structures because they work as a unit providing stability and support to the knee, especially during strenuous activities.
A common injury to the knee is the “unhappy triad,” which involves damage to the ACL, MCL, and medial meniscus. When the foot is planted on the floor, the knee is slightly bent, and a forceful twisting or rotating on the knee occurs, an individual is likely to experience this “unhappy triad.”