Most frequently seen in athletes or those who participate in sports, ACL injuries range in severity from small strains to a complete ACL tear. The ACL, or anterior cruciate ligament, is one of the four major ligaments of the knee and the main support system for the knee. Patients with ACL injuries often complain of a "pop" sound from inside the joint, immediate, intense pain and a feeling of the knee giving out.

A chondral defect refers to damage to the articular cartilage located at the end of bones. Articular cartilage is an elastic, smooth, soft tissue which allows bones to interact with each other without friction or pain. It acts as a shock absorber for force applied to the joint during movement. Specific to the knee joint, damage can occur at the end of the femur (thigh bone), the proximal tibia (lower leg bone), or the posterior aspect of the patella (kneecap).

Knee tendonitis, also known as patellar tendonitis occurs when the patella tendon is overstressed, causing swelling and irritation. The condition is often called jumper's knee. Patellar tendonitis develops gradually.

The lateral collateral ligament (LCL) is the ligament located in the knee joint. Ligaments are strong and thick bands of tissue that connect bone to bone. The LCL is the ligament that runs along the outside of the knee joint. It runs from the bottom of the thigh bone to the top of the lower-leg bone. Its function is to help keep the knee stable.

A loose body is a small piece of cartilage or bone that breaks off and moves freely around the knee in joint fluid, or synovium. Loose bodies can hinder the joint moment by getting caught in flexion and extension movements.The fragments can lead to damage to the articular cartilage, causing osteoarthritis.

The medial collateral ligament (MCL) is located on the inner part of your knee, but it’s actually outside the joint itself. Ligaments hold bones together and add stability and strength to a joint. The MCL connects the top of the tibia, or shinbone, to the bottom of the femur, or thighbone.

Injuries to the meniscus cartilage of the knee are among the most common injuries encountered in sports. Many athletes, especially runners and those in contact sports, are highly susceptible to tears. However, individuals at any age can experience tearing of the meniscus. Tears can be acute and traumatic, involving injury, or chronic and degenerative in nature.

Sometimes called degenerative joint disease or degenerative arthritis, osteoarthritis (OA) is the most common chronic condition of the joints, affecting approximately 27 million Americans. OA can affect any joint, but it occurs most often in knees, hips, lower back and neck, small joints of the fingers and the bases of the thumb and big toe. In normal joints, a firm, rubbery material called cartilage covers the end of each bone.

The patella, or better known as the kneecap, dislocations occur when the patella shifts out of place leaving the patellofemoral groove. Dr. Austin Chen, orthopedic knee and sports medicine specialist in Boulder Colorado works with patients to treat patellar dislocations.

The posterior cruciate ligament is located in the back of the knee. The PCL is one of several ligaments that connect the femur (thighbone) to the tibia (shinbone). Its function is to keep the shinbone stabilized and from moving backwards too far. The PCL can be injured by a direct force with a bent knee. Dr. Austin Chen, knee specialist serving Greater Boulder, Colorado, is available to both diagnose and treat PCL injuries.