The radiological methods to determine patellar height described in the literature are variable, not reliable and depend on the chosen ratio. The purpose of this paper is to describe another method of measuring patellar height on sagittal MRI using the true articular cartilage patellotrochlear relationship. An analysis of magnetic resonance (MR) examinations of 66 consecutive patients was performed. The most common diagnoses were meniscal or anterior cruciate ligament pathologies. No patient suffered from patellofemoral complaints. Measurements on sagittal MR images included different parameters using the articular cartilage of the patella and the trochlea. The ratio patella : trochlea of the cartilage baselines was measured in percentages and described as patellotrochlear index. The measurements were assessed at two different times by three raters under blinded conditions. The mean patellotrochlear index was 31.7% (CI: 12.5-50.0; range -5.0 to 61.1%; SD +/-11.6). The intraobserver variability showed only in the "second observer" a difference of the mean values of the two different measurements (t=2.189; P=0.032). The interobserver correlation was high and significant (0.663-0.893; P=0.000). Our results indicate that the patellotrochlear index is a reliable and precise method to determine the exact articular correlation of the patellofemoral joint and the patellar height. The results represent the average patellotrochlear index in the normal population without patellofemoral complaints. Measurements of the articular cartilage congruence can be helpful to define an underlying pathology of patellar height, such as patella alta or infera.

Different surgical techniques have been described to correct trochlear dysplasia, without clear descriptions of the various types of trochlear dysplasia. In describing trochlear dysplasia, there exist no clear criteria to distinguish between decreased trochlear depth (heightened trochlea floor) and flattened lateral and/or medial condylar height. The current study aims to build a database of axial MRI measurements of normal and abnormal trochlear shape to create a foundation for the selection of the necessary surgical correction to more normal trochlear anatomy. We prospectively examined 152 subjects: 30 patients with patellar instability due to trochlea dysplasia and 122 subjects without any symptoms or objective findings related to the patellofemoral joint. MRI was performed in both groups. The height of the medial and lateral condyle, and the center of the trochlea was measured on axial MR images. The height of these different locations was compared to the total width of the femoral condyle and expressed in percentages. The statistical analysis was conducted with the Student's t test at SPSS software. For intraobserver reliability 20 randomly taken MRI were evaluated twice. The intraobserver reliability was determined by calculating the kappa values investigated parameter. In normal subjects, the height of the lateral condyle was 81% of the width of the femoral condyle (100 units),the trochlear central height was 73%, the medial condylar height was 76%. In patients with patellar instability, the lateral condylar height was 82% and showed no significant difference compared to the normal group (P = 0.082). The trochlear central (77%) and medial condylar height (79%) were significantly different (P < 0.001) compared to the normal subjects. The location of pathology in patients with patellar instability was decreased lateral condylar height in five cases (16.6%) and decreased central/medial height in 25 cases (83.4%). A height of the lateral condyle <77% was documented to be pathologic. There was also a significant difference (P < 0.001) between males and females comparing the different heights of the trochlea to the total width of the femoral condyle. The resultant percentages of all three height measurements, the lateral, central, and medial heights, were greater in males than in females. The intraobserver reliability was perfect for all investigated parameters. In conclusion, (1) the presented measurement scheme on axial MRI is a reliable method to calculate the height of the trochlea in different locations, (2) a more objective assessment of the trochlear pathology is possible, (3) in five of six cases the pathology is located in the center and/or medial trochlea, and (4) in our series of patellofemoral instability patients, most would benefit from a deepening trochleaplasty as the surgical procedure of choice to correct dysplasia.

This study examined the effect of four different methods for treating intrasubstance meniscal lesions. Forty patients (21 men, 19 women; age 30.4 years, range 16-50) with an isolated and symptomatic painful horizontal grade 2 meniscal lesion on the medial side (documented with MRI) were included. Patients were randomly assigned by the birth date to one of four treatment groups: group A, conservative therapy (n = 12); group B, arthroscopic suture repair with access channels (n = 10); group C, arthroscopic minimal central resection, intrameniscal fibrin clot and suture repair (n = 7); and group D, arthroscopic partial meniscectomy (n = 11). The average length of follow-up was 26.5 months (range 12-38 months). Follow-up evaluation consisted of clinical examination with the findings recorded according to the IKDC protocol, radiographs, and control MRI. Group A had 75% normal or nearly normal final evaluation at follow-up, group B 90%, group C 43%, and group D 100% normal or nearly normal at follow-up. These short-term results indicate that intrasubstance meniscal lesions can be treated best by performing partial meniscectomy. To preserve the important function of the meniscus, arthroscopic suture repair with access channels might give even better medium- to long-term results. Conservative treatment is often not satisfactory. Additionally, our findings show that MRI examinations are not superior to accurate clinical examinations.

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We present a comprehensive histologic study of neurologic structures in 18 static and dynamic knee structures of 8 cadaveric knees. Qualitative and quantitative measurements of the incidence of free nerve endings in the structures were recorded. The highest amounts of afferent nerve fibers type IVa were found in the retinacula, the patellar ligament, the pes anserinus, and in the ligaments of Wrisberg and Humphry; the lowest amount was found in the anterior cruciate ligament. There is a positive correlation between the number of mechanoreceptors per standardized area unit and the clinical presentation of certain knee disorders.