The article should include the following areas for consideration:

· An Introduction section which should introduce the topic and place in context for the reader.

· A Background section which should provide a general overview of the condition including incidence, description of likely mechanisms of injury, clinical presentation, common radiological appearances, treatment outcomes and/or complications

· A Case Study section which focuses on a hypothetical patient journey from injury to outcome

· A Conclusion section which pull the assessment to a close.

The topic is : lipohemathrosis of knee

The first description of lipohemarthrosis was made by Kling in 1929. ‘ He demonstrated that there was a fat mixed with blood in 40% of the hemorrhagic fluid specimens aspirated from traumatized knees. Pierce2 suggested that fat may also enter the joint cavity through a synovial tear, explaining the presence of lipohemarthrosis in those cases without demonstrable fractures. In view of our findings, one would question whether his patients indeed had only soft-tissue injuries. In 1942 Holmgren3 reviewed 65 cases of knee fractures in which cross table lateral roentgenograms had been done. There were fat fluid levels in approximately half of his cases. In 1967 Berk4 reported an additional six cases. Three of these patients had subtle fractures that perhaps would not have been found without the presence of fat fluid to encourage taking additional roentgenograms. In 1977, Saks, Rosenthal, and Ferris5 described visualization of the articular capsule on vertical beam lateral roentgenograms due to the presence of fat lying both within and outside of the joint space. They stressed the importance of this finding in demonstrating subtle tibial plateau fractures. This sign, however, was not present in any of our patients. ***Reference (1)

Lipohemarthrosis is a joint effusion that contains fat and blood mixed with the synovial fluid. Due to gravity, the lighter fat floats above the synovial fluid. The floating fat above the synovial fluid has a lower X-ray attenuation, which is seen as fluid-fluid level on imaging studies. Lipohemarthrosis was first described by horizontal beam technology several decades ago Traumatic lipohemarthrosis is considered synonymous with an intra-articular fracture and occurs as a result of extrusion of fat and blood from bone marrow into the joint space after an intraarticularfracture .Lipohemarthrosis can also be visualized on cross-sectional imaging (such as CT) due to differences in X-ray attenuation of fat, blood products, and synovial fluid. Due to the differences in T1 and T2 relaxation times of fat, blood products and synovial fluid, lipohemarthrosis is also demonstrated on MRI scans. Traumatic lipohemarthrosis of the knee***Reference (2)

Lipohemarthrosis is defined as the presence of intra-capsular floating fat in a joint cavityTraumatic knee injury represents the most common cause, and lipohemarthrosis is widely considered pathognomonic for acute fracture.Lipohemarthrosis occurs in 35–41% of knees presenting with intra-articular fracture.Thus, lipohemarthrosis is an important sign, since knee trauma accounts for nearly 532,000 annual visits to the emergency department in the United States. ***Reference (3)

whereas lipohemarthrosis, the presence of lipid material and blood, is very accurate for an intraarticular fracture penetrating the cartilaginous parts of the joint [1]. Almost the only differential diagnosis is a rupture of the infrapatellar fat pad (Hoffa’s fat pad), as the latter resides within the capsula of the knee. Lipohemarthrosis can be found in approximately 40% [2] of all intraarticular fractures of the knee and evolves at the latest 3 h after the trauma [3]; however, gravity and a certain time of rest are needed to depict the characteristic double fluid–fluid layer which is characteristic of lipohemarthrosis Three bands can normally be distinguished: the top band consists of fatty material, whereas the following band below is composed of serum and serous joint effusion. The cellular parts of the blood, i.e., erythrocytes and leukocytes, sediment due to gravity and form the lowest band [6]. Current clinical routine is the puncture of the knee joint, however a potential risk of injection or the painfulness of the procedure renders it uncomfortable to the patient. As an alternative, lipohemarthrosis can be evaluated using different imaging methods comprising conventional X-rays, ultrasound, CT, and MRI***Reference (4)

Lipohemarthrosis is very suggestive of an intraarticular fracture. It can be assessed by various tomographic and non-tomographic methods, each of which has its advantages and disadvantages. An accurate diagnosis helps the patient during his treatment as it paves the way to either conservative treatment or surgical intervention. ***Reference (5)

Case stydy

The first image is a lateral plain radiograph, with a linear interface between 2 soft-tissue densities, just superior to the posterior aspect of the patella. This linear interface indicates lipohemarthrosis, resulting from entry of marrow fat into the joint cavity. Lipohemarthrosis can also be detected when fat globules are observed on needle aspiration of a hemarthrosis. The second image is a sagittal MRI that shows the interface in greater detail, with blood products posterior and fat anterior. (The fracture is not shown in these images.) Emergency physicians should be vigilant for lipohemarthrosis on radiographs of traumatized joints, just as they are vigilant for the fat pad sign on radiographs of traumatized elbows. While the fat pad sign indicates displacement of a fat pad by an effusion, lipohemarthrosis indicates release of fat into the joint cavity, ie, an effusion composed of both blood and fat.(6)

A 32-year-old female presented to the ED minor injury unit with the inability to stand or bear weight on her left leg after a fellow dancer knocked her left knee at an unknown angle and the patient fell to the nightclub dance floor. She had instant severe pain and felt the left kneecap move laterally. The paramedics had managed her injury with an inflatable split. the patient was transferred to the hospital by ambulance and entering to an accident and emergency department Her main complaint was of pain. She had no other neurologic symptoms, no history of dislocations, and no predisposing risk factors.

the first Examination revealed a laterally dislocated patella, with the knee held in slight flexion and tenting of the skin over the superolateral patellar surface (Figure 1). Peripheries were warm and well perfused with distal pulses intact. The patient had no obvious long bone deformity or bruising, and she had normal light-touch sensation. She was refusing attempts at relocation because of the pain.

then the doctor refers the patient to the x-ray dept.the radiographer justifies the request and checks the patient details also the LMB.AP and Lateral views were done for her.

X-ray images revealed a left lateral patellar dislocation with no obvious associated fracture (Figure 2). The radiographer could not obtain skyline views because the patient was unable to sufficiently flex her knee. Postimaging, after the ED physician and another senior physician made 2 further attempts at closed reduction without success, the patient’s leg was placed in a Richards splint, and the plan was to reattempt reduction in the morning.

Computed tomography (CT) scan of the left knee revealed a fracture of the medial patellar margin, associated lipohemarthrosis, and a small donor fragment of bone lying in the dependant portion of the lipohemarthrosis laterally (Figure 3).

The patient was discussed in the morning trauma meeting, and the decision was made to take her to the operating room for closed or open relocation of the patella with or without stabilization with suture anchors of the medial patellofemoral ligament. An orthopedic surgeon performed manipulation under anesthesia and achieved a closed reduction after 20 minutes of firm manipulation (Figure 4). The patient had a large knee joint effusion postreduction, the patella tracked in correct alignment, and the knee was able to flex and extend in a full range of motion. Postoperative x-rays confirmed appropriate position and joint effusion but showed no other fractures or complications

The surgeon reported that the reduction was particularly difficult and required significant force. He was only minutes away from performing an open reduction when the patella was successfully reduced. The surgeon’s opinion was that an incarcerated fat pad initially blocked reduction. His technique for reduction with an incarcerated fat pad included firm pressure to the lateral patella while lifting it anteriorly and medially to help alleviate the blockage. This case highlights how a bony fragment or incarcerated fat pad can cause irreducibility by locking the patella in a lateral position.

Postoperatively, the patient complained of moderate pain requiring analgesia. She was placed in a full-weight-bearing Richards splint for 2 weeks. When she was seen in the clinic at 2-week follow-up, the patient reported instability with stairs and some pain. She had a Beighton score of 9/9. On examination, both knees hyperextended >5 degrees with a grade I effusion of the left knee. She had no medial or lateral joint line tenderness, and her range of motion was 0-80 degrees. She was referred to a physiotherapist for vastusmedialis exercises and conservative management in a hinged knee brace. ***Reference (6)