[Posteromedial corner of the knee]

The posteromedial corner of the knee is increasingly being recognized in orthopedic surgery, traumatology and musculoskeletal radiology. The medial collateral ligament consists of a superficial part and a deep part. The posteromedial corner consists of the posterior oblique ligament (POL), the oblique popliteal ligament (OPL), the semimembranosus tendon and its arms, the posteromedial joint capsule and the posterior horn of the medial meniscus. The structures provide stability to the knee joint with respect to valgus stress, rotational stability as well as with respect to anterior and posterior translation. Injuries are frequently associated with other severe injuries of the knee. This underlines the importance of recognizing the structures and their injuries on magnetic resonance imaging (MRI), in order to enable adequate therapy.

[Advanced cartilage imaging for detection of cartilage injuries and osteochondral lesions]

BACKGROUND

Osteochondral defects represent a main risk factor for osteoarthritis of the ankle.

OBJECTIVES

The aim of this article is to provide an overview of current optimal clinical cartilage imaging techniques of the foot and ankle and to show typical osteochondral injuries on imaging.

MATERIALS AND METHODS

A thorough literature search was performed and was supported by personal experience.

RESULTS

Cartilage imaging of the foot and ankle remains challenging. However, advanced morphological and quantitative magnetic resonance (MR) imaging techniques may provide useful clinical information, for example, concerning cartilage repair surgery. Compared to MRI, MR arthrography (MR-A) and CT arthrography (CT-A) have higher sensitivity with respect to detection of osteochondral defects. Regarding smaller joints of the foot, mainly advanced osteoarthritic changes are detected on conventional radiography; only in rare cases, MR and CT imaging of these smaller joints is of relevance.

CONCLUSIONS

While at the smaller joints of the foot cartilage imaging only plays a minor role, at the ankle joint cross-sectional cartilage imaging using CT and MRI becomes more and more important for clinicians due to emerging therapeutic options, such as different osteochondral repair techniques.

T2-relaxation time of cartilage repair tissue is associated with bone remodeling after spongiosa-augmented matrix-associated autologous chondrocyte implantation

OBJECTIVE

To investigate whether T2 relaxation time measurements of cartilage repair tissue and structural changes of the knee joint are associated with subchondral bone architecture after spongiosa-augmented matrix-associated autologous chondrocyte implantation (MACI).

DESIGN

Both knees of 25 patients (25.5 ± 7.8y; 10 women) were examined preoperatively and 2.7 years after unilateral spongiosa-augmented MACI with 3T magnetic resonance (MR) imaging. Cartilage composition was assessed using T2 relaxation time measurements, subchondral trabecular bone microstructure was quantified using a 3D phase-cycled balanced steady state free-precision sequence. Structural knee joint changes were assessed using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). The Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score was used for the postoperative description of the area that underwent MACI. Correlations were assessed using Spearman's rank correlation coefficients.

RESULTS

Hypertrophy of the cartilage repair tissue was found in 2 of 25 patients, both after a MACI procedure at the patella, 21 patients showed congruent filling. In subchondral bone of the cartilage repair compartment, apparent trabecular thickness was significantly higher in compartments with elevated cartilage T2 (n = 17; 0.37 ± 0.05 mm) compared to those showing no difference in cartilage T2 compared to the same compartment in the contralateral knee (n = 8; 0.27 ± 0.05 mm; P = 0.042). Significant correlations were found between the overall progression of WORMS and the ipsilateral vs contralateral ratio of average trabecular thickness (r = 0.48, P = 0.031) and bone fraction (r = 0.57, P = 0.007).

CONCLUSIONS

After spongiosa-augmented MACI, T2 values of cartilage repair tissue and structural knee joint changes correlated with the quality of the underlying trabecular bone.

Alignment does not influence cartilage T2 in asymptomatic knee joints

PURPOSE

To investigate whether the static knee alignment affects articular cartilage ultrastructures when measured using T2 relaxation among asymptomatic subjects.

METHODS

Both knee joints (n = 96) of 48 asymptomatic volunteers (26 females, 22 males; 25.4 ± 1.7 years; no history of major knee trauma or surgery) were evaluated clinically (Lysholm, Tegner) and by MRI (hip-knee-ankle angle, standard knee protocol, T2 mapping). Group (n = 4) division was as follows: neutral (<1° varus/valgus), mild varus (2°-4° varus), severe varus (>4° varus) and valgus (2°-4° valgus) deformity with n = 12 subjects/group; n = 24 knees/group. Regions of interest (ROI) for T2 assessment were placed within full-thickness cartilage across the whole joint surface and were divided respecting compartmental as well as functional joint anatomy.

RESULTS

Leg alignment was 0.7° ± 0.5° varus among neutral, 3.0° ± 0.6° varus among mild varus, 5.0° ± 1.1° varus among severe varus and 2.5° ± 0.7° valgus among valgus group subjects and thus significantly different. No differences between the groups emerged from clinical measures. No morphological pathology was detected in any knee joint. Global T2 values (42.3 ± 2.3; 37.7-47.9 ms) of ROIs placed within every knee joint per subject were not different between alignment groups or between genders, respectively.

CONCLUSION

Static frontal plane leg malalignment does not affect cartilage ultrastructure among young, asymptomatic individuals as measured by T2 quantitative imaging.

LEVEL OF EVIDENCE

Cross-sectional study, Level II-III.

Association of metabolic risk factors with cartilage degradation assessed by T2 relaxation time at the knee: data from the osteoarthritis initiative

OBJECTIVE

To evaluate the association of metabolic risk factors with severity and 2-year progression of early degenerative cartilage changes at the knee, measured with T2 relaxation times in middle-aged subjects from the Osteoarthritis Initiative.

METHODS

Cartilage segmentation and T2 map generation were performed in knee 3T magnetic resonance images from 403 subjects ages 45-60 years without radiographic osteoarthritis (OA). The influence of risk factors on baseline T2 and longitudinal progression of T2 was analyzed using linear regression, adjusting for age, sex, and other OA risk factors.

RESULTS

Four metabolic risk factors, i.e., high abdominal circumference (P < 0.001), hypertension (P = 0.041), high fat consumption (P = 0.023), and self-reported diabetes mellitus (P = 0.010), were individually associated with higher baseline T2. When the 4 metabolic risk factors were considered in a multivariate regression model, higher T2 remained significantly associated with abdominal circumference (P < 0.001) and diabetes mellitus (P = 0.026), and there was a trend for high fat consumption (P = 0.096). For the individual risk factors, only diabetes mellitus remained associated with higher baseline T2 after adjustment for body mass index (BMI). After adjustment for BMI, baseline T2 increased in a dose-response manner with the number of metabolic risk factors present (P = 0.032 for linear trend), and subjects with ≥3 metabolic factors (versus <3) had significantly higher baseline T2 (mean difference 1.2 msec [95% confidence interval 0.3, 2.1]; P = 0.011). Metabolic risk factors were not significantly associated with increases in T2 during followup.

CONCLUSION

Metabolic risk factors are associated with higher T2, suggesting that increased cartilage degeneration may be caused by modifiable metabolic disorders.