Knee pain can occur on all sides of the knee, and the location of the pain often indicates its cause. Knee injuries can damage any of the tendons, ligaments or bursae---fluid-filled sacs surrounding the knee joint---as well as the bones, cartilage and ligaments that make up the knee joint itself. The knee is a complex joint, and knee pain signals the presence of a structural imbalance in the body.
Sprains and Strains
The most common type of ligament damage is called a sprain, whereas the most common type of muscle damage is called a strain. Sprains and strains involve a tearing or stretching of the tissue beyond its normal stretch capabilities. The severity of sprains and strains are graded on a scale of one to three, with grade three sprains and strains being the most severe. Grade three sprains and strains involve a complete tear or rupture of the ligament or muscle, and may require surgical repair. There are several ligaments and muscles surrounding the knee joint that are vulnerable to sprains and strains.
On the outside aspect of the knee is the lateral collateral ligament, or LCL, and the tendinous insertion of the iliotibial band. According to the American Academy of Family Physicians, excessive varus or outward stress applied to the knee may damage the LCL. The person will experience pain immediately and will be forced to discontinue any sport or activity. The same is true for the medial collateral ligament, or MCL, on the inside edge of the knee when excessive valgus or inward stress on the knee is applied. Damage to the MCL usually is followed by pain and swelling on the inside aspect of the knee. Excessive valgus stress may also injure the pes anserine, which is the conjoined tendon of the sartorius, gracilis and semi-tendinosus muscles.
Tendinitis and Bursitis
Tendinitis and bursitis are common yet painful causes of knee pain. Tendinitis involves the inflammation of a tendon, often near the location of the tendon's insertion on bone. Bursitis involves the inflammation of a bursa that lies between a tendon and a bone. Bursae are intended to decrease friction between the tendons and bone during movement.
On the outside aspect of the ---the side of the knee facing away from the body---the iliotibial band may become inflamed and painful. Iliotibial band tendinitis is caused by excessive friction between the iliotibial band and the knee's lateral femoral condyle. It's a common musculoskeletal injury in endurance athletes, such as marathoners and road cyclists. On the inside aspect of the knee, pes anserine bursitis occurs when the tendinous aspects of the sartorius, gracilis and semi-tendinosus muscles inflame the pes anserine bursa.
On the front aspect of the knee, a person may develop jumper's knee, which results from inflammation of the patellar tendon, and often is seen in teenagers, especially boys, following growth spurts. Activities such as running and stair climbing worsen anterior knee pain in those with jumper's knee. According to the Clinical Sports Medicine website, anterior knee pain, including the pain associated with jumper's knee, is one of the most common presenting symptoms in a clinical sports medicine practice.
Cruciate Ligament Tears and Plica Syndrome
Just as structures on the outside of the knee are at risk for injury, so too are structures on the inside of the knee, including the anterior and posterior cruciate ligaments and the plica, which are an extension of the knee's synovial membrane.
According to the Sports Injury Clinic website, a torn anterior cruciate ligament, or ACL, injury is a relatively common knee injury among female athletes. People who tear their ACL may hear an audible pop and, like a tear of the posterior cruciate ligament, or PCL, will experience considerable swelling and pain in their knee and restricted mobility in the knee on the involved side. The knee will also feel unstable with cruciate ligament tears.
Plica syndrome occurs when the plica---remnants of the fetal stage of development----become inflamed and painful following repetitive knee motion. According to eOrthopod.com, A person with plica syndrome will experience pain and possibly a snapping sensation along the inside of the knee as the knee is bent.
Meniscus Tears
Unless a person has undergone knee joint replacement surgery, each knee joint possesses two menisci---crescent-shaped fibrous cartilage that pads and reinforces the knee joint. A lateral meniscus tear results when a person experiences a forceful torquing of their knee, which may occur when a runner or other type of athlete suddenly alters direction. Those who experience lateral meniscus tears typically develop knee pain and knee joint locking. Despite its unique anatomy, a medial meniscus tear is comparable to a lateral meniscus tear, in that the involved knee joint will experience periodic catching or locking. Those with medial meniscus tears may find squatting or twisting activities problematic.
