الفهرس 
GROSS ANATOMY OF KNEE JOINTOnly 14 pages are availabe for public view
 |  | from | 71 |  |  |
| | | from | 71 | | |
Abstract
The US can effectively be used to evaluate many structures of the knee. The resolution of US is maximized when evaluating superficial structures.
Therefore, evaluation of superficial structures such as the extensor mechanism of the knee, the MCL, and joint recesses can be quite successfull Because resolution is generally decreased as the depth of the structure being evaluated increases, US is less effective for deep structures as well as intra-articular structures, such as cartilage or intrinsic knee ligaments.
There are several advantages of using US evaluation of the knee when compared to other imaging methods for particular indications. One advantage is the decreased cost when compared to MRI when evaluating for a focal soft tissue abnormality. In addition, there are advantages gained by patient interaction, enabling a detailed history and direct correlation with findings from the physical examination. Another important advantage of ultrasound is the ability to perform a dynamic evaluation.
Indications for US of the knee vary depending on the experience and knowledge of the sonographer and availability of competing imaging methods.
In general, US performs best in the evaluation of a superficial structure where there is a focused clinical question. One of the most common indications for US of the knee is to determine the cause of posterior knee or calf pain or mass, in particular, the presence of a Baker’s or popliteal cyst. US is helpful in that a Baker’s cyst can be diagnosed or excluded, and complications of a Baker’s cyst, such as rupture, can also be assessed. A ruptured Baker’s cyst may produce a sterile cellulitis that extends into the ankle region.
Another common indication for knee US involves the extensor mechanism of the knee and surrounding soft tissues and bursae. For example, the specific question of a quadriceps or patellar tendon tear can be addressed with US. Other tendon problems, such as tendinosis, can also be diagnosed. Distention or inflammation of the adjacent bursa can easily be diagnosed, and US guided percutaneous aspiration can be performed to exclude infection.
US can also be used for the evaluation of joint effusion and to help differentiate simple joint fluid, complex joint fluid, and synovitis.
The deep and intra-articular structures of the knee are more difficult to evaluate with US while MRI is usually considered the standard of care. For example, although US evaluation of the menisci, the cruciate ligaments, and the articular cartilage has been describe
The development of high-resolution technology has led to increasing acceptance of US as a valuable diagnostic tool in musculoskeletal imaging. The afford ability and availability of US versus other imaging modalities is of great appeal. The prerequisites for excellent results include high-resolution US equipment, through knowledge of the regional anatomy, and recognition of the normal appearances and common pitfalls. Assessment can be rapid and offers the advantage of dynamic testing. It is important to recognize when US is appropriate or inappropriate for answering the clinical question at hand. With experience at acquiring and interpreting images, US can play a role in the assessment of pathologic conditions involving the knee joint.
High –resolutione US can early detect:
1- Knee effusion either serous ,bloody or lipohemarthrosis , either hetrogenus or hemogenus and associated with popliteal cyst or not.
2- Fluid fluid level means intra-articular fracture with escape of bone marrow fat and blood forming lipohemarthrosis.
3- Tendon tears.
4- Musclar fibers tear.
5- Tear of collateral ligament.
6- Can suggest acute meniscual tear.
7- But still ACL and PCL out of reach of US.