Osteoarthritis (OA) is the most common cause of musculoskeletal pain and disability. It is a chronic degenerative disorder of multifactorial etiology, including acute and/or chronic insults from normal wear and tear, age, obesity and joint injury. The true pathogenesis remains poorly understood. OA is characterized by a degradation of the articular cartilage, resulting in an alteration of its biomechanical properties, which in turn contributes to a focal loss of articular cartilage, loss of joint space, osteophyte formation, focal areas of synovitis, per articular bone remodeling and sub chondral cysts , OA presents with symptoms such as joint pain, stiffness, motion limitations, motor and sensory dysfunction and functional impairments, thus, preventing patients from participating in regular physical activities , The common sites of OA appear on the knees, hands, and hips, whereas knee OA is the most common .~Pain is the most frequent complaint for patients with knee OA to seek medical attention. If left untreated, pain and stiffness can result in a loss of physical function and independence during daily activities. The presence of OA-related knee pain has also been associated with increased risks of physical disability in the community .~Many studies have revealed a discrepancy between patients' reports of pain and their radiographic findings , a plausible option is that the pain originates from the myofascial trigger points (MTrPs) in the surrounding muscles (myofascial pain) and cannot be visualized by imaging.~The term myofascial pain is defined as the complex of sensory, motor, and autonomic symptoms caused by MTrPs , MTrPs, hyperirritable spots found in the skeletal muscles, are associated with hypersensitive palpable nodules located in a taut band. The spots are painful on compression and may produce characteristic referred pain, referred tenderness, motor dysfunction, and autonomic phenomena.~All studies found a high prevalence of myofascial pain in knee OA patients . study of OA patients, MTrPs were found in all participants, especially in the medial head of the gastrocnemius (92%) and the vastus medialis muscle (67%).~The treatment of MPS includes:~In activation of trigger points, relaxation of taut bands, and breaking the pain-spasm-ischemia-pain cycle. The most widely used treatment methods for MPS are education, exercise, non steroidal anti-inflammatory drugs (NSAIDs), superficial and deep heat, electrotherapy, laser therapy, and local injections.~Laser treatment :~Is non- invasive and painless and can be easily administered in therapy units for a wide range of conditions .~Recently, high-intensity laser therapy (HILT) was introduced to the field of physical therapy. The advantage of HILT over Low level laser therapy(LLLT) is that HILT is able to reach and stimulate the large and/or deep joints that are difficult to reach in LLLT .~The use of HILT has been proven to significantly reduce pain . Previous studies describe the anti-inflammatory, anti-edematous, and analgesic effects of HILT, thus justifying its use in the therapy of pain .
This study was conducted to investigate the effect of High intensity laser therapy( HILT) on pressure pain threshold, serum cortisol level, passive knee range of motion, and changes of functional disability in patients with active myofascial trigger points(MTrPs) pain associated wit knee osteoarthritis(OA) .