Interpretation of the Common MRI Findings in Patients with Painful Knee Joint

Nowadays knee joint pain is a major public health issue and for an appropriate treatment option, it is important to have a clear understanding of the cause of pain as well as to identify the exact location of the pain. In the initial evaluation of acute knee pain, radiological findings help physicians in taking decisions regarding appropriate treatment. Besides conventional radiography and computed tomography (CT), Magnetic resonance imaging (MRI) is often used to diagnose the reason for knee problems. This study it is tried to evaluate the common MRI findings in patients with painful knee joints. The sample population comprised 77 outpatients had an age range between 14 to 66 years, representing male 70.13% and Female 29.87%.The study shows that the maximum numbers of patients were in the 26-30 years age group, which exposed that young people are more affected with knee pain. In this study, it is found that joint effusion is the most common pathology frequently found in 59.74% of patients followed by meniscus injury 53.24%, anterior cruciate ligament (ACL) tear 36.06%, Lateral meniscus injury 16.88%, Posterior cruciate ligament (PCL) tear 7.8%, Bone marrow contusion 22.07%, Osteoarthritis12.98%, Medial collateral ligament (MCL) injury 3.89%, Lateral collateral Ligament (LCL) 0%, Fracture 6.49%, Chondromalacia1.3%, Baker cyst 1.3%. Though knee pain can be diagnosed by other imaging modalities, MRI can often provide strong evidence to support one.

Plain X-ray can establish fractures and degenerative changes of the knee. In cases of knee joint trauma, clinical examination along with radio-graphs and even CT scan is not enough to diagnose many internal conditions of this joint. MRI, due to its excellent soft tissue contrast resolution and multi-planar imaging capabilities provides significant advantages over other imaging techniques in the evaluation of traumatic injuries of knee joint (Yadav and Kachewar, 2013;Prickett et al., 2001).
MRI can accurately diagnose the ligament injuries of knee joint, which is an ideal technique in the diagnosis of ligament injuries, and should be used as a routine examination method (Pompan, 2012). So, MRI affects the diagnosis and management of the knee injuries by decreasing the number of arthroscopic procedures, improving clinician diagnostic certainty, and assisting in management decision (Kamran et al., 2015). It has been found that the disruption of a knee ligament is commonest pathology in patients having post traumatic knee pain (Roy et al., 2020). It is important to develop a mechanistic approach to associate the imaging findings with their anatomic relevance (Miller and Yu, 2010).
MRI is a type of scan that uses a magnetic field, radio waves, and a computer to create detailed pictures of the inside of your body. Unlike an X-ray, which takes pictures of your bones, a knee MRI lets physician see bones, cartilage, tendons, ligaments, muscles, and even some blood vessels. The test can show a range of problems, including: Damaged carti-lage, Torn tendons or ligaments, Bone fractures, Oste-oarthritis, Infections, Tumors, etc. MRI is a non-invasive imaging technique that does not involve exposure to ionizing radiation (Peterfy et al., 2004).
Knee joint pain may either have traumatic origin or non-traumatic origin like infection or inflammation. Optimum treatment is hampered sometimes due not to identify the exact lesion causing pain. MRI can demonstrate the exact nature and extent of bony as well as soft tissue abnormality (Escala et al., 2006). This has increased the use of MRI in evaluation of patients of knee pain (Mehta et al., 2015).

MATERIALS AND METHODS:
This study consists of 77 adult cases from MRI department, Popular Medical College and Hospital. All patients had prior history of knee pain, injuries (Sports, Trauma), Swelling, difficulty in bending knee etc. Siemens Magnetom Avanto1.5 tesla MRI machine was used for diagnosis of patients' painful knee. The following protocols were used:  T2-tse-sagital,coronal,and axial plan  T1-tse-sagittal,coronal,and axial plan  PD-tse-fs-sagittal, coronal, and axial plan  PD-tse -sagittal plan  T2-tse -sag-p2-2mm (Especially for ACL injury).
 Inclusion criteria: Patients of either sex with age more than 14 having acute or chronic painful knee.  Exclusion criteria: Patients, who could not cooperate for MRI examination, have undergone prior surgical procedures and who had metallic implant or metallic situ.
All images were reported by radiologists, and a consensus diagnosis was given by two radiologists in controversial cases. After collection, Data was checked, verified, and processed to reduce error. Then it was analyzed by computer.

RESULTS:
Among all imaging technique, MRI becomes the preferred imaging technique for the evaluation of the painful knee following injury because of its ability to detect soft tissue abnormality (meniscus and cruciate /collateral ligament tears) and fracture that cannot be detected by plain X-Ray. Joint pain is the most common complaint in prior history and the second most common complaint is sports injury. From Table  1 it can be shown that the maximum numbers of patients were in 26-30 years age group and from which it can also be observed that young people are affected more. A number of factors may be involved in this case such as excess weight, lack of muscle flexibility or strength, certain sports or occupations, previous injury, lack of being active, etc.   Fig 3). Male are more affected than female. This is because male are generally more active than female and travel a lot. Hence their knees are exposed to more wear and tear.
Also they are at more risk of injury. It also demonstrates that Right knee (58.44%) is more affected than left knee (41.56%) (   From Table 3 it can be demonstrated that 27 patients have ACL involvement in knee pain and complete ACL tear is more (77.78%) than partial ACL tear (22.22%). It can be observed from Table 4 that out of 10 no of patients having knee pain due to PCL, buckling (40%) is the common findings.   Table 6 showed that medial meniscus injury is in more cases (54, 70.13%) and it may also be demonstrated that posterior horn is more affected than anterior horn. It may be concluded from Table 7 that Small joint effusion (30, 38.96%) is very common pathology among patients of painful knee joint.

DISCUSSION:
Present study was an observational analysis of the various causes of a painful knee detected by MR imaging. In this study, the mean age was 40.5 years and it is male dominance. Our results are in concordance with those of Yadav et al. (2013) who described a mean age of 36.70±14 years and a male preponderance in their study (Yadav and Kachewar, 2013). Male preponderance was also seen in study done by some authors ( , 2017). Tear was the commonest pathology affecting the ACL, most being acute in nature. PCL involvement pathology in our study was 7.8%, which may be compared to the 5.78% incidence reported by Singh et al. (2004) Buckling (40%) is the common findings in PCL involvement. One-third of our patients had bone contusion which compares well with the existing literature (28.3%) (Wright et al., 1995;Sohail et al., 2015;Mathis et al., 1998). Critical ACL tears were usually due to bone contusions in our study. Similar association was reported previous studies (McCauley et al., 1994;Spindler et al., 1993;Arumugam et al., 2015).
Baker cyst was very less common in present study. MRI detects an associated disorder in cystic cases. An association of popliteal cyst with joint effusion, meniscus tear and ACL tear has been previously reported (Miller et al., 1996;Sansone et al., 1995). MR has been established as an effective non-invasive modality for identifying the knee pathology. The study aimed to highlight the role of MRI in diagnosing the cause of painful knee and strengthen its superiority over the conventional imaging (X-rays) and CT scan thereby ensuring a better clinical management.

Limitations
Some of limitations those were frequently faced during this study are summarized below: 1) Cardiac Pacemaker, Cochlear Implants & some orthopedics prosthesis patient are prohibited for MRI. 2) Cost effective is relatively more than X-ray or CT scan. 3) The sample was taken purposively, so it may not reflect the actual situation. 4) MRI is not available in many rural areas of Bangladesh. 5) Wheel chair or bed patient can't take directly to the MRI. 6) Claustrophobic & disoriented patients are very difficult to do MRI. 7) MRI takes long time for completing whole scan.

CONCLUSION:
Knee pain is very common nowadays and will affect most of us at some point during our lives. From the observations of present study it can be said in conclusion that MRI would be the best choice for diagnosing the reason of knee pain in combination with conventional x-rays. It may affect in diagnosis the exact reason of knee pain as well as management of the knee injuries by reducing the number of arthroscopic procedures, improving doctors' diagnostic certainty, and assisting in management decision. MRI of knee may often be useful during the surgery and also to see the healing progress after surgery of knee. For the rapid, accurate diagnosis with a noninvasive examination of painful knee, MRI examination can be considered as an ideal technique. It had also been demonstrated that MRI is a cost effective technique by reducing unnecessary surgical and arthroscopic interventions (Shah et al., 2014).

ACKNOWLEDGEMENT:
Firstly, I am grateful to Almighty Allah to give me the ability to complete this project. This research was supported by Department of Biomedical Engineering and Medical Physics of Bangladesh University of Health Sciences. I am thankful to all who provided expertise that greatly assisted the research. Also I would like to thank my parents and my family for supporting me mentally throughout writing this study.

CONFLICTS OF INTEREST:
The author's declared there are no conflicts of interest to publish the present work.