Morphometric evaluation of the knee joint with conventional magnetic resonance imaging (MRI) in patients with patellar chondromalacia

INTRODUCTION AND OBJECTIVE: Patellar chondromalacia is an important cause of anterior knee pain, especially in middle-aged patients. Detecting the findings that may cause chondromalacia at an early stage prevents the development of patellar chondromalacia with precautions and treatments; In the presence of patellar chondromalacia, these precautions and treatments slow down or stop the progression of chondromalacia or sometimes regress it. It has been observed that patellar chondromalacia is due to many reasons such as age, gender, obesity, trauma, anatomical variations and pathologies of the patellofemoral joint (PFJ). In our study, we evaluated the relationship between the presence and severity of patellar chondromalacia with age, gender, PFJ morphology and subcutaneous fat tissue thickness around the knee by magnetic resonance imaging (MRI). Our aim is to draw attention to parameters other than age and gender in the etiology of patellar chondromalacia, which can be changed by behavioral changes and medical and/or surgical treatments. MATERIAL AND METHOD: A total of 726 knee MRI examinations which were carried out between 01.12.2019 - 20.05.2020 at the central campus MRI unit of the Radiology Clinic of Sakarya University Faculty of Medicine Training and Research Hospital and registered with PACS, were retrospectively evaluated for patellar chondromalacia. A standard knee MRI protocol was used. Examinations of individuals with a history of trauma and/or fractures and dislocations secondary to trauma, who have undergone open or arthroscopic knee surgery, the presence of significant intra-articular effusion and/or hemarthrosis, and patellofemoral osteoarthritis and examination of individuals under the age of 18 were excluded from the study. Additionally, exclusion criteria included MRI of poor quality based on artefacts which are due to technical factors and/or patient movement. The chondromalacia stage of the individuals was determined, their age and gender were recorded. Then, some morphometric measurements were made regarding the anatomical structure of the patella and trochlea together with the position of the patella, and the thickness of the subcutaneous fat tissue around the knee was measured. 208 examinations of sick individuals and 256 studies of healthy individuals were included in the study. The relationship between age, gender, morphometric measurements made in patellofemoral junction and subcutaneous adipose tissue thickness with the presence and severity of chondromalacia were evaluated. The compatibility of quantitative data to normal distribution was tested with the Kolmogorov Smirnov test. While Pearson correlation test is used in the statistical analysis of quantitative data showing a normal distribution; Sperman correlation test was used for statistical analysis of quantitative data that did not show a normal distribution. Chi-square test was used for categorical variables. RESULTS: 464 knee MRI examinations were included in our study, of which 47,6% (n = 221) were male and 52,4% (n = 243) were female. The mean age of the individuals was 44,75 ± 11,68 (18-79) years. Patellar chondromalacia was found in 44,83% (n = 208) of the examinations evaluated. Among the patients with patellar chondromalacia, the most common stage IV cartilage damage was observed with a rate of 39,9% (n = 83). 64,9% (n = 135) were female and 35,1% (n = 73) were male of the patient group. There was a very high level of statistically significant difference in terms of gender in the chondromalacia group (p <0,001). It was observed that there was a higher rate of chondromalacia in female gender. The mean age of the patellar chondromalacia group was 48,38 ± 11,65 years. The mean age of the individuals with chondromalacia were higher than those without, there was a very high statistically significant difference in terms of age (p <0,001). Among the morphometric measurements related to the anatomy of the patella, a statistically significant difference was found between the ratio of patella facet lengths and the medio-lateral and apex-basis length measurements of the patella (p <0,05); There was no significant difference in the patellar facet angle measurement (p> 0,05). Among the morphometric measurements related to the anatomy of the trochlea, a statistically significant difference was found between the medial facet length of the trochlea, the ratio of the trochlear facet lengths, the lateral and medial trochlear inclination, the trochlear groove angle, the trochlear groove depth, the ratio of the trochlear groove to the trochlear depth, the trochlear angle and distance between the tuberositas tibia and the trochlear groove (p <0,05); There was no significant difference in trochlear lateral facet length measurement (p> 0,05). Among the morphometric measurements related to the position of the patella, a statistically significant difference was found between the bisect offset, lateral patellofemoral angle, Insall-Salvati index and the angle between patella and quadriceps tendon (p <0,05); There was no significant difference in the measurement of patellar tilt angle, lateral patellar tilt angle, patellotrochlear index and patella-patellar tendon angle (p> 0,05). Subcutaneous adipose tissue thickness measurement increasement was also statistically significant among the patellar chondromalasia cases (p <0,05). CONCLUSION: In our study, the morphological structure of the patella and trochlea, patellofemoral joint alignment and subcutaneous fat tissue thickness were evaluated. It was observed that trochlear morphology and pathologies of patellofemoral alignment were more effective in the development of patellar chondromalacia than the morphological structure of the patella. In addition, it was also noticed that the increase in subcutaneous fat tissue thickness associated with higher grade of chondromalacia.