The knee is the largest joint in the body and is one of the most complex. It is a made up of four components: bones, cartilage, ligaments and tendons. The knee moves like a door hinge and enables a person to bend and straighten their legs so they can carry out daily activities like sitting, squatting, jumping and running.
Knee injuries are very common especially among sportsmen and the elderly. Since the knee is a complex joint, it is vulnerable to a variety of injuries. Most knee injuries include dislocations, tears and sprains of the soft tissue, and fractures around the knee. Swollen and painful knees are two of the most common indicators of a knee injury. Sometimes the knee may also catch or lock up. Several knee injuries may also result in instability – a feeling that the knee is going to give out. Let us take a look at some common knee injuries.
1. Kneecap (Patellar) Fractures
The kneecap functions as a shield for the knee joint, thus it can easily be broken when subjected to a strong force. Patellar fractures account for at least 1 percent of all fractures and will often require surgery to heal as it is a floating and moving bone. Patellar fractures can be caused by direct blows (i.e. motor vehicle collision or falls). Swelling and pain in the front of the knee are two of the most prevalent indicators of patellar fractures. Other symptoms can include: Inability to walk or straighten the knee and bruising.
2. Patellar Tendon Tears
Tendons are made up of strong cords of fibrous tissue that attach the muscles to the bones. The patellar tendon is a ligament that connects to two different bones, the patella and the tibia. It works with muscles in the front of the thigh to straighten the leg. Small tears to this tendon can make it difficult to walk. A large tear of the patellar tendon is a disabling injury and usually require surgery and physical therapy to regain full knee function.
A very strong force is required to cause the patellar tendon to tear. During a fall, direct impact to the front of the knee can cause tears to the tendon. The patella tendon may also be torn when a person jumps and lands incorrectly. A tearing or popping sensation is felt during patellar tendon tears. This will result in a painful and swollen knee. Other symptoms include: Bruising, cramping, tenderness, indentation at the bottom of the kneecap and difficulties walking.
3. Anterior Cruciate Ligament (ACL) Injuries
The ACL is one of the four main ligaments that connect the femur to the tibia. The ACL runs diagonally in the knee’s middle and prevents the tibia from sliding out in front of the femur. It also provides rotational stability to the knee. Injured ligaments are considered “sprains” and are graded on a severity scale. Most ACL injuries are either complete or near complete tears.
Changing direction rapidly, coming to a sudden stop, landing from a jump incorrectly or direct collision may result in ACL tear. When there is an ACL tear, a ‘popping’ noise followed by the feeling that the knee has given out. A painful and swollen knee usually follows. Other symptoms include loss of full range of motion, tenderness along the joint line and discomfort while walking.
4. Posterior Cruciate Ligament (PCL)
The posterior cruciate ligament is located in the back of the knee. It prevents the tibia from moving too far back. PCL tears make up less than 20% of injuries to the knee ligaments. Injuries that tear the PCL often damage some other ligaments or cartilage in the knee, as well. PCL injuries are often due to a powerful force when the knee is bent. Eg. Striking the knee against a dashboard during a car accident or a sportsman falling on the knee when it is bent.
After a PCL injury, people often think that they only have a minor knee problem and continue to go about their daily lives. However, symptoms that may develop include, swollen knee, wobbling sensation in the knee or trouble walking or bearing weight on the knee. Over time, a PCL tear may lead to osteoarthritis in the knee.
5. Collateral Ligaments
Collateral ligaments are found on the sides of the knee. This includes Medial collateral Ligament (MCL) and Lateral Collateral Ligament (LCL). Collateral ligaments control the sideway motion of the knee and brace it against unusual movement. As mentioned above, injured ligaments are considered “sprains” and are graded on a severity scale.
Athletes who participate in contact sports are likely to injure their collateral ligaments. MCL often occurs as a result of a direct blow to the outside knee. This pushes the knee inwards towards the other knee. A direct blow to the inside of the knee pushes the knee outwards and may injure the LCL. The MCL is injured more often than LCL.