The oblique popliteal ligament: an anatomic and MRI investigation.

PURPOSE: Despite being the largest ligament on the posterior aspect of the knee, relatively little is known about the normal morphology of the oblique popliteal ligament (OPL). The aim of this study was to investigate the detailed anatomy of the OPL in cadavers and healthy volunteers. METHODS: The posterior knee was investigated in 25 cadaver lower limbs (mean age 76 ± 9.5 years; 7 men) by dissection, histology, and serial plastination and in 14 healthy individuals (mean age 23 ± 3.2 years; 11 men) using magnetic resonance (MR) imaging. OPL morphology, attachments sites, ligament length and width, relationship to surrounding structures and histological composition were recorded. Intraobserver reliability was assessed using intraclass correlation coefficients. RESULTS: The OPL is a distinct expansion of the semimembranosus (SM) tendon and sheath, which courses superolaterally to attach to the posterolateral joint capsule or fabella (when present), at the medial margin of the lateral femoral condyle. The ligament blends with the joint capsule medially and laterally, serves as an attachment site for plantaris, and has connections with popliteus. In 70% of dissections, the OPL divided into two bands, separated by small branches of the middle genicular neurovascular bundle that pierced the posterior joint capsule. Differences in mediolateral length were noted between dissection and MR imaging (43.6 ± 6.2 vs. 57.6 ± 4.4 mm; p < 0.001). At its medial and lateral attachments, the OPL was 23.2 ± 6.9 and 17.4 ± 8.7 mm wide (proximodistal), respectively. The OPL was predominantly composed of transverse collagen layers, with little elastin. While visible on axial MR scans, delineation of its most lateral extent was difficult. Repeatability of selected measurements ranged from good to almost perfect. CONCLUSIONS: The OPL is a distinct ligament with identifiable anatomical limits. Based on its morphological characteristics, it appears more tendinous than ligamentous in nature. A better understanding of the OPL may help define its importance in the assessment and treatment of posterior knee injuries.

Articularis genus: an anatomic and MRI study in cadavers.

BACKGROUND: The articularis genus muscle is closely associated with the anterior aspect of the knee joint and may act to elevate or retract the suprapatellar bursa. Its form and function are poorly understood. The purpose of this study was to define the morphology of the articularis genus and its relationship to the suprapatellar bursa. METHODS: The articularis genus muscle was investigated in twenty-two human lower limbs obtained from eleven donors (six men and five women; mean age at death, eighty-three years). Eighteen of these limbs underwent magnetic resonance imaging (MRI) followed by dissection. The number, length, physiological cross-sectional area, attachment sites, and orientation of individual fascicles, muscle bundles, and whole muscles were recorded. The remaining four limbs underwent immunohistochemical analysis to determine muscle fiber types. RESULTS: The articularis genus comprised multiple layered muscle bundles originating from the anterior, anterolateral, and/or anteromedial surfaces of the distal third of the femur. Distal attachment sites included the proximal and/or posterior wall of the suprapatellar bursa, the deep surface of the distal tendon of the vastus intermedius, and the medial and lateral aspects of the knee joint capsule. On dissection, the muscle was observed to consist of a mean of seven muscle bundles (range, four to ten), but only a mean of four bundles were observed on MRI scans (p < 0.0001). The mean cross-sectional area of the articularis genus (and standard deviation) was 1.5 ± 0.7 cm2, and its mean fascicular length and bundle physiological cross-sectional area were 5.9 ± 1.0 cm and 0.2 ± 0.1 cm2, respectively. The articularis genus displayed a mixed fiber type, with the proportion of type-I fibers varying among specimens (range, 39.9% to 76.4%). CONCLUSIONS: These findings highlight the complex and variable anatomy of the articularis genus, particularly with respect to the number of bundles and the distal attachment sites. Distinguishing the superficial bundles of the articularis genus from the vastus intermedius on MRI can be difficult. CLINICAL RELEVANCE: Given its relationship to the anterior aspect of the knee joint and its association with the suprapatellar bursa, the articularis genus may be a neglected cause of undifferentiated anterior knee pain.

Lateral hip pain: findings from magnetic resonance imaging and clinical examination.

STUDY DESIGN: Prospective cross-sectional study. OBJECTIVES: To examine the radiological and physical therapy diagnoses of lateral hip pain (LHP), and determine the validity of selected clinical variables for predicting gluteal tendon pathology. BACKGROUND: LHP is frequently encountered by clinicians. Further investigation is required to establish the specific pathologies implicated in the cause of LHP, and which clinical tests are useful in the assessment of this problem. METHODS AND MEASURES: Forty patients with unilateral LHP underwent a physical therapy examination followed by magnetic resonance imaging (MRI) studies. Three radiologists analyzed the images of both hips for signs of pathology. Interobserver reliability of the image analyses, the agreement between the physical therapy and radiological diagnoses, and the validity of the clinical tests were examined. RESULTS: Gluteus medius tendon pathology, bursitis, osteoarthritis and gluteal muscle atrophy (predominantly affecting gluteus minimus) were all implicated in the imaging report of LHP. While prevalent in symptomatic hips, abnormalities were also identified in asymptomatic hips, particularly relating to the diagnosis of bursitis. The strength of agreement between radiologists was variable and little agreement existed between the physical therapy and radiological diagnoses of pathology. Nine of the 26 clinical variables examined in relation to gluteal tendon pathology had likelihood ratios above 2.0 or below 0.5, but the associated 95% confidence intervals were large. CONCLUSIONS: The diagnosis of LHP is challenging and our results highlight some problems associated with the use of MRI as a diagnostic reference standard. This factor, together with the imprecise point estimates of the likelihood ratios, means that no firm conclusions can be made regarding the diagnostic utility of the clinical tests used in the assessment of gluteal tendon pathology.

Patterns of injury in patients with radiographic occult fracture of neck of femur as determined by magnetic resonance imaging.

The purpose of the present study was to review retrospectively our experience with MRI in patients over the age of 50 who present to the emergency department with inability to weight bear following a fall and whose initial radiographs were normal. The study was designed to establish the incidence and pattern of bone and soft tissue injuries in these patients and to determine whether MRI could provide predictive information regarding length of hospital stay. The present study demonstrated the practicality of a protocol using MRI to obtain rapid definitive diagnosis in patients with occult fractures of the pelvic ring and neck of femur. The present study also suggests that significant prognostic information with regard to length of hospital stay can be obtained from an early MRI scan.