Anterior interval release (AIR) is a type of arthroscopic knee surgery performed to alleviate pain and associated symptoms caused by scar tissue (or fibrosis) accumulation in the anterior region of the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

, behind and under the knee cap (or patella), in a condition called

arthrofibrosis Arthrofibrosis (from Greek: ''arthro-'' joint, ''fibrosis'' – scar tissue formation) has been described in most joints like knee, hip, ankle, foot joints, shoulder (frozen shoulder, adhesive capsulitis), elbow (stiff elbow), wrist, hand joints as ...

. In normal, asymptomatic

s, this anterior compartment of the knee comprises mobile, scar-free tissues such as the infrapatellar (Hoffa's) fat pad. With progression, scar tissue (or fibrosis) leads to closure of the anterior interval, tethering the

patella tendon The patellar tendon is the distal portion of the common tendon of the quadriceps femoris, which is continued from the patella to the tibial tuberosity. It is also sometimes called the patellar ligament as it forms a bone to bone connection when t ...

and causing pain, loss of

range of motion Range of motion (or ROM), is the linear or angular distance that a moving object may normally travel while properly attached to another. It is also called range of travel (or ROT), particularly when talking about mechanical devices and in mechanic ...

, damage to

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

, and/or pain, among other symptoms. Diagnosis of

or scar tissue in the anterior interval can consist of clinical signs such as a positive Hoffa test, loss in

flexion, and/or diminished superoinferior

patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

mobility, with supplementation by magnetic resonance imaging (or MRI) Post-surgical rehabilitation should be conservative in nature, focusing on maintaining joint mobility via early motion to avoid reformation of scar tissue. Early motion may be promoted by specific mobility exercises and use of continuous passive motion. Restoration of joint

may be augmented by specialized bracing devices. Weight bearing is delayed appropriately post-surgically to promote control of swelling, pain, and joint irritation. Strengthening is delayed to a minimum of 6 weeks, often several months, post-operatively. The origins leading to

are unclear. They frequently have involved previous knee injury or

trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...

, such as

anterior cruciate ligament The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formation ...

reconstruction surgery. More subtle origins of

fibrotic Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perman ...

contracture in the anterior interval have also been attributed to plica (or naturally occurring folds in the knee joint lining) that become stiff and restrictive.

References

{{reflist Orthopedic surgical procedures