To better understand why the location of knee pain can be so telling, it helps to learn about the structures of the knee and the various conditions that can affect them.
This article takes a concise look at the anatomy of the knee joint and describes the processes and conditions that cause pain in the different aspects (parts) of the knee.
Between the femur and tibia are two C-shaped pieces of cartilage, called the meniscus, that function as shock absorbers. There are also fluid-filled sacs, called bursae, between the bones of the knees that ensure smooth movement.
The knee joint is surrounded by a membrane, called the synovium, that produces a thick fluid, called synovial fluid, that helps keep the meniscus slippery.
The knee bones are connected with fibrous bands of tissues known as ligaments that provide the knee with stability. The ligaments that support the knee are:
Anterior cruciate ligament (ACL): This ligament prevents the femur from sliding backward on the tibia as well as the tibia sliding forward on the femur. Posterior cruciate ligament (PCL); This ligament prevents the femur from sliding forward on the tibia as well as the tibia from sliding backward on the femur. Medial collateral ligament (MCL): This is the ligament that prevents the knee from sliding sideways toward the center of the body. Lateral collateral ligament (LCL): This is the ligament that prevents the knee from sliding sideways away from the center of the body.
Tendons connect the knee bones to the muscles of the leg to move the knee joint.
Bursitis: This is the inflammation of the bursae commonly caused by an acute knee injury, a repetitive overuse injury, or a systemic (whole-body) inflammatory condition like rheumatoid arthritis or gout. Chondromalacia: This is the deterioration of the patella, also known as “runner’s knee,” most commonly caused by repetitive stress. Knee osteoarthritis: Thi is a non-inflammatory form of arthritis, also known as “wear-and-tear” arthritis. Arthritis in the patellofemoral compartment of the knee capsule, between the patella and femur, commonly causes upper knee pain. Patella tracking syndrome: This is a condition often due to a traumatic injury that causes the patella to shift out of place as the leg is bent or straightened.
Osgood-Schlatter disease: This is a condition common in children in which the tendons of the knees pull on the knee’s growth plate during rapid growth spurts. Osteochondritis dissecans: This is an uncommon disorder that causes the knee meniscus starts to loosen and, in some cases, detach from the bone. Patellar tendonitis: This is the inflammation of the tendon of the kneecap, also known as “jumper’s knee,” that commonly occurs in athletes who jump or run Patellofemoral instability: This is a condition, once known as traumatic patellar dislocation, in which the patella gets moved out of the groove that connects it to the bottom of the femur.
Bursitis: This is a form of bursitis called pes anserine bursitis that occurs in between the tibia and the tendons of the hamstring muscle. Knee osteoarthritis: This occurs when arthritis develops in the medial compartment of the knee. Medial collateral ligament injuries: Also known as an MCL tear, this is often caused by sudden turning, twisting, or “cutting” motions in sports like skiing, football, basketball, and volleyball. Medial meniscus tears: This is usually a sport-related injury caused when you forcefully twist or rotate the knee, such as occurs during football or soccer.
Knee osteoarthritis: This can occur when arthritis develops in the lateral compartment of the knee. Iliotibial band syndrome: This is a condition common in distance runners and impact cyclists in which the strong band of tissues that starts at the hip and runs along the outer thigh (called the iliotibial band) is injured. Lateral collateral ligament injuries: Also known as an LCL tear, this is most commonly caused by a direct blow to the inside of the knee. Lateral meniscus tear: This is when the cartilage on the lateral aspect of the knee is torn, often the result of excessive weight bearing and twisting knee motions, such as occurs with skiing or basketball.
Anterior cruciate ligament tear: Also known as an ACL tear, this is an injury that can occur during sports, motor vehicle collisions, severe falls, and work-related injuries. Tricompartment osteoarthritis: This is a form of osteoarthritis in which all three compartments of the knee (medial, lateral, and patellofemoral) have arthritis.
Baker’s cyst: This is a fluid-filled sac that occurs when excess synovial fluid sees through the back of the knee capsule (due to things like severe osteoarthritis or an injury of the meniscus). Posterior cruciate ligament injuries: Also known as a PCL tear, this usually occurs when the knee is directly hit, such as during contact sports like soccer, football, or rugby.
As a rule of thumb, see a healthcare provider if your knee pain was caused by a forceful impact or is causing significant swelling, pain, redness, or warmth around the joint.
You have severe knee pain. You hear a popping sound or feel your knee give out at the time of an injury. You cannot move your knee. You start limping and cannot bear weight on the knee. You have knee swelling after a blow to the knee.
