MRI features of cystic lesions around the knee

Arthroscopic treatment of meniscal cysts in the horse

REASONS FOR PERFORMING STUDY

To describe the clinical symptoms, treatment, and outcome of meniscal cysts in horses. These structures have not been previously described in the literature as a potential cause of lameness in the horse.

HYPOTHESIS

Meniscal cysts are an uncommon condition of the femorotibial joint but can be a significant cause of lameness. Symptoms can be resolved by arthroscopic excision.

METHODS

Records of horses diagnosed with meniscal cysts and treated by cyst excision and meniscal debridement at 2 surgical practices were reviewed. Clinical outcome was determined by repeat veterinary examination and contact with owner.

RESULTS

Seven cases of meniscal cyst were treated with arthroscopic cyst excision and meniscal debridement. Five of 7 horses had lameness attributable to femorotibial joint pathology, while the remaining 2 horses had meniscal cysts found incidentally during diagnostic arthroscopy for the treatment of osteochondritis dissecans of the lateral trochlear ridge of the femur. Five of 6 horses with long-term follow-up were sound and a 7th horse was improved 11 months after surgery.

CONCLUSIONS AND POTENTIAL RELEVANCE

Meniscal cysts, while uncommon, can be associated with progressive lameness in the horse. Surgical excision of the cysts results in resolution or improvement of symptoms, without evidence of recurrence on follow-up examination.

MR findings of synovial disease in children and young adults: Part 2

Synovium is the thin membranous lining of a joint. It produces synovial fluid, which lubricates and nourishes the cartilage and bone in the joint capsule. Synovial diseases in children can be classified as normal structures as potential sources of pathology (synovial folds: plicae, infrapatellar fat pad clefts), noninfectious synovial proliferation (juvenile idiopathic arthritis, hemophilic arthropathy, lipoma arborescens, synovial osteochondromatosis, pigmented villonodular synovitis, reactive synovitis), infectious synovial proliferation (pyogenic arthritis, tuberculous arthritis), deposition disease (gouty arthropathy), vascular malformation, malignancy (metastasis) and intra-/periarticular cysts and cyst-like structures. Other intra-articular neoplasms, such as intra-articular synovial sarcoma, can mimic synovial disease in children.

The management of solitary tumours of Hoffa's fat pad

Hoffa's fat pad (HFP) of the knee is affected by a variety of tumours and tumour-like conditions. HFP can be affected by diffuse or solitary, focal disease. This paper reports a consecutive series of 19 cases of solitary symptomatic HFP tumours. The commonest presenting symptom was anterior knee pain. All patients underwent open excision after diagnostic magnetic resonance imaging (MRI). Histology revealed varied diagnoses with the commonest being pigmented villonodular synovitis (PVNS) and ganglia. American Knee Society scores improved from 76 pre-operatively to 96 post-operatively with an improvement in functional scores from 92 to 100. In conclusion the majority of solitary HFP tumours are benign and may be either cystic or solid. MRI and plain radiographs are the imaging of choice. The definitive treatments of both cystic and solid tumours should be selective arthrotomy and excision biopsy. All patients in this series reported substantial improvement in symptoms following surgery.

Subchondral cysts create increased intra-osseous stress in early knee OA: A finite element analysis using simulated lesions

AIM OF STUDY

To investigate the role of intra-osseous lesions in advancing the pathogenesis of Osteoarthritis (OA) of the knee, using Finite Element Modeling (FEM) in conjunction with high-resolution imaging techniques.

METHODS

Twenty early stage OA patients (≤ Grade 2 radiographic score) were scanned with a prototype, cone-beam CT system. Scans encompassed the mid-shaft of the femur to the diaphysis of the proximal tibia. Individual bones were segmented to create 3D geometric models that were transferred to FE software for loading experiments. Patient-specific, inhomogeneous material properties were derived from the CT images and mapped directly to the FE models. Duplicate models were also created, with a 3D sphere (range 3-12 mm) introduced into a weight-bearing region of the joint, mimicking the size, location, and composition of a subchondral bone cyst (SBC). A spherical shell extending 1mm radially around the SBC served as the sample volume for measurements of von Mises equivalent stress. Both models were vertically loaded with 750 N, or approximately 1 body weight during a single-leg stance.

RESULTS

All FE models exhibited a physiologically realistic weight-bearing distribution of stress, which initiated at the joint surface and extended to the cortical bone. Models that contained the SBC experienced a nearly two-fold increase in stress (0.934 ± 0.073 and 1.69 ± 0.159 MPa, for the non-SBC and SBC models, respectively) within the bone adjacent to the SBC. In addition, there was a positive correlation found between the diameter of the SBC and the resultant intra-osseous stress under load (p = 0.004).

CONCLUSIONS

Our results provide insights into the mechanism by which SBC may accelerate OA, leading to greater pain and disability. Based on these findings, we feel that patient-derived FE models of the OA knee - utilizing in vivo imaging data - present a tremendous potential for monitoring joint mechanics under physiological loads.

Large intra-articular anterior cruciate ligament ganglion cyst, presenting with inability to flex the knee

A 41-year-old female presented with a 3-month history of gradually worsening anterior knee pain, swelling and inability to flex the knee. Magnetic resonance imaging (MRI) revealed a large intra-articular cystic swelling anterior to the anterior cruciate ligament (ACL), extending into the Hoffa's infrapatellar fat pad. Following manipulation under anaesthesia and arthroscopic debridement of the cyst, the patient's symptoms were relieved with restoration of normal knee motion. ACL ganglion cysts are uncommon intra-articular pathological entities, which are usually asymptomatic and diagnosed incidentally by MRI. This is the first reported case of an ACL cyst being so large as to cause a mechanical block to knee flexion.

Mucoid degeneration of the posterior cruciate ligament: a case report

We report a case of mucoid degeneration of the posterior cruciate ligament (PCL) who complained of knee joint pain on flexion. Magnetic resonance imaging (MRI) showed a diffusely thickened PCL with increased signal intensity on the T2-weighted sequence. A few intact fibers were observed with continuous margin from origin to insertion. Arthroscopy revealed yellow crumbly tissues among the PCL fibers. There was no tear of PCL fibers, thus their tension was preserved. Curettage of degenerative tissue and decompression of the PCL resulted in symptom relief without instability of the knee joint. Notably, the MRI features of mucoid degeneration of the cruciate ligament can be mistaken for those of partial tear of the ligament.

Cyst-like lesions of the knee joint and their relation to incident knee pain and development of radiographic osteoarthritis: the MOST study

OBJECTIVE

To determine whether intra- and periarticular cyst-like lesions of the knee are associated with incident knee pain and incident radiographic knee osteoarthritis (OA).

DESIGN

The Multicenter Osteoarthritis (MOST) Study is a cohort of individuals who have or are at high risk for knee OA. Using a nested case-control study design, we investigated the associations of cyst-like lesions (Baker's, meniscal and proximal tibiofibular joint (PTFJ) cysts, and prepatellar and anserine bursitides) with (1) incident pain at 15- or 30-month follow-up and (2) incident radiographic OA at 30-month follow-up. Baseline cyst-like lesions were scored semiquantitatively using the Whole Organ Magnetic Resonance Imaging Score (WORMS). Conditional logistic regression models were used to assess the relation between these lesions and the outcomes, adjusting for potential confounding factors (i.e., cartilage loss, meniscal damage, bone marrow lesions, synovitis and joint effusion, which were also scored using WORMS).

RESULTS

Incident knee pain study included 157 cases and 336 controls. Prevalence of meniscal and PTFJ cysts in the case group was twice that in the control group [9 (6%) vs 9 (3%) and 9 (6%) vs 10 (3%), respectively]. Incident radiographic OA study included 149 cases and 298 controls. Prevalence of grade 2 Baker's cysts and PTFJ cysts in the case group was approximately four times that in the control group [16(11%) vs 9 (3%) and 6 (4%) vs 3 (1%), respectively]. However, none of the cyst-like lesions was associated with incident pain or radiographic OA after fully adjusted logistic regression analyses and correction of P-values for multiple comparisons.

CONCLUSION

None of the analyzed lesions was an independent predictor of incident knee pain or radiographic OA. Intra- and periarticular cyst-like lesions are likely to be a secondary phenomenon seen in painful or OA-affected knees, rather than a primary trigger for incident knee pain or radiographic OA.

Longitudinal assessment of cyst-like lesions of the knee and their relation to radiographic osteoarthritis and MRI-detected effusion and synovitis in patients with knee pain

Introduction

The purpose of the present study was to determine the prevalence of cystic lesions and cyst-like bursitides in subjects with frequent knee pain and to assess their relation to radiographic osteoarthritis (OA) severity; to describe bilaterality and size fluctuation of the lesions over 6 months; and to assess relations between the prevalence of synovium-lined lesions communicating with the joint capsule and severity of magnetic resonance imaging (MRI)-detected effusion and synovitis.

Methods

One hundred and sixty-three subjects (total 319 knees) aged 35 to 65 with chronic, frequent knee pain were included. Imaging with 3 Tesla MRI was performed at baseline and 6-month follow-up with the same protocols as those used in the Osteoarthritis Initiative. Severity of radiographic OA was assessed using the Kellgren-Lawrence grade (0 to 4). Severity of effusion and synovitis was graded 0 to 3 based on the Whole Organ Magnetic Resonance Imaging Score system. The associations of cysts and cyst-like bursitides and severity of radiographic OA, MRI-detected effusion and synovitis were analyzed using logistic regression controlling for clustering by person. The Wilcoxon signed-rank test was used to determine whether there was a significant change in the size of lesions between baseline and follow-up.

Results

At least one lesion (any type) was present in 222 (70%) knees. The most prevalent lesions were popliteal cysts (40%, 128/319), followed by subgastrocnemius bursitis (15%, 49/319) and proximal tibiofibular joint cysts (8%, 26/319). Bilateral lesions were seen in 49% of the subjects. Only popliteal cysts and subgastrocnemius bursitis showed a significant change in size (P < 0.001). No trend was observed between prevalence of any of the cyst-like lesions analyzed and the increasing radiographic OA severity. Increasing prevalence of subgastrocnemius bursitis was associated with increasing severity of effusion (P = 0.0072) and synovitis (P = 0.0033).

Conclusions

None of the cyst-like lesions analyzed seems to be a marker of radiographic OA severity in knees with chronic frequent pain. Subgastrocnemius bursitis may be used as a marker of effusion/synovitis severity. Bilateral cyst-like lesions are relatively commonly observed in people with chronic knee pain.

Posterior knee pain

Posterior knee pain is a common patient complaint. There are broad differential diagnoses of posterior knee pain ranging from common causes such as injury to the musculotendinous structures to less common causes such as osteochondroma. A precise understanding of knee anatomy, the physical examination, and of the differential diagnosis is needed to accurately evaluate and treat posterior knee pain. This article provides a review of the anatomy and important aspects of the history and physical examination when evaluating posterior knee pain. It concludes by discussing the causes and management of posterior knee pain.

The association between subchondral bone cysts and tibial cartilage volume and risk of joint replacement in people with knee osteoarthritis: a longitudinal study

Introduction

To examine the natural history of subchondral bone cysts and to determine whether knee cartilage loss and risk of joint replacement is higher in knees with cysts, compared with those with bone marrow lesions (BMLs) only or those with neither BMLs nor cysts.

Methods

The symptomatic knee in 132 subjects with knee osteoarthritis (OA) was imaged by using magnetic resonance imaging at baseline and 2 years later. Tibial cartilage volume, subchondral bone cysts, and BMLs were measured by using validated methods. Knee arthroplasty over a 4-year period was ascertained.

Results

Bone cysts were present in 47.7% of subjects, 98.1% of whom also had BMLs. Over a 2-year period, 23.9% of subjects had cysts progress, 13.0% developed new cysts, and 11.4% had cysts regress. Bone cysts at baseline were associated with lower medial and lateral tibial cartilage volume compared with those with BMLs only or those with neither (P for trend 0.004 and <0.001, respectively). Annual medial cartilage volume loss was greatest in those with bone cysts compared with those with BMLs only or those with neither (9.3%, 6.3%, and 2.6%, respectively; P for trend, <0.001). As the severity of bone abnormality in the medial compartment increased from no BMLs or cysts present, to BMLs only, to subchondral bone cysts present, the risk of knee replacement was increased (odds ratio, 1.99; 95% confidence interval (CI), 1.01 to 3.90; P = 0.05).

Conclusions

When cysts are present, cartilage loss and risk of knee replacement are higher than if only BMLs are present, suggesting that cysts identify those most likely to benefit from prevention of disease progression. As cysts can regress, they may also provide therapeutic targets in knee OA.

MR imaging of intra- and periarticular soft tissues and subchondral bone in knee osteoarthritis

Osteoarthritis of the knee has to be considered a disease of the whole joint. Magnetic resonance imaging allows superior assessment of all joint tissues that may be involved in the disease process, such as the subchondral bone, synovium, ligaments, and periarticular soft tissues. Reliable MR imaging-based scoring systems are available to assess and quantify these structures and associated pathology. Cross-sectional and longitudinal evaluation has enabled us to understand their relevance in explaining pain and structural progression.