The medical model of history, examination and investigation forms the bedrock of diagnosis and management of all patients. The essence is the recognition of patterns of symptoms and signs. In the modern era there are an increasing number of non-medical resources ranging from web-based information, computer diagnostic aids and non-specialist healthcare professionals to provide a diagnosis and commence management of a wide range of conditions, including knee problems. We analysed the quality and patterns of clinical presentation in order to answer the question how closely clinical symptoms and examination findings correlate to diagnosis based on MRI scan and/or arthroscopic findings. The analysis was a dataset of a consecutive series of patients, aged 18 to 45, with no past history of knee problems or end stage arthritis, presenting to a single specialist triage physiotherapist, working within an integrated knee service, who fully completed a standardised knee assessment proforma of presenting symptoms and signs at a large district general hospital. The study comprises 86 patients and 98 knees. We analysed this data based on diagnostic findings of MRI scan or arthroscopy to provide definitive intra-articular diagnosis. Based on standard textbook descriptions of common presentations, we went on to define the patients' presentation history and examination as typical or atypical, with typical meaning the symptoms and signs correlated with the diagnosis. The null hypothesis is that patients have a high chance of typical presentations for common knee conditions. In the 75% of patients with a significant intra-articular pathology we found the majority had chondral rather than meniscal tears 1.7 to 1. Forty four percent of patients had atypical symptoms and 71% had atypical clinical signs, 30% and only 26% of the cohort had both typical symptoms and signs together, reflecting a surprisingly low positive predictive probability of symptoms and signs in this group of patients, particularly those with chondral lesions which was 44%. In this cohort, 57% of the cohort has 3 or more multiple diagnoses. In the diagnostically normal group, 43% had symptoms and signs typical for a meniscal tear. We conclude that clinical symptoms and signs surprisingly inaccurate in guiding intra-articular pathology within the knee, even in a sub-set considered the easy and accurate to assess. The number of multiple diagnoses and the incidence of false positive results also means that simplistic interpretations of non-definitive diagnoses and linear causation of pain pathways should be treated cautiously.

Bioactive functional scaffolds are essential for support of cell-based strategies to improve bone regeneration. Adipose-tissue-derived-stromal-cells (ASC) are more accessible multipotent cells with faster proliferation than bone-marrow-derived-stromal-cells (BMSC) having potential to replace BMSC for therapeutic stimulation of bone-defect healing. Their osteogenic potential is, however lower compared to BMSC, a deficit that may be overcome in growth factor-rich orthotopic bone defects with enhanced bone-conductive scaffolds. Objective of this study was to compare the therapeutic potency of human ASC and BMSC for bone regeneration on a novel nanoparticulate β-TCP/collagen-carrier (β-TNC). Cytotoxicity of β-TCP nanoparticles and multilineage differentiation of cells were characterized in vitro. Cell-seeded β-TNC versus cell-free controls were implanted into 4 mm calvarial bone-defects in immunodeficient mice and bone healing was quantified by µCT at 4 and 8 weeks. Tissue-quality and cell-origin were assessed by histology. β-TNC was non-toxic, radiolucent and biocompatible, lent excellent support for human cell persistence and allowed formation of human bone tissue by BMSC but not ASC. Opposite to BMSC, ASC-grafting significantly inhibited calvarial bone healing compared to controls. Bone formation progressed significantly from 4 to 8 weeks only in BMSC and controls yielding 5.6-fold more mineralized tissue in BMSC versus ASC-treated defects. Conclusively, β-TNC was simple to generate, biocompatible, osteoconductive, and stimulated osteogenicity of BMSC to enhance calvarial defect healing while ASC had negative effects. Thus, an orthotopic environment and β-TNC could not compensate for cell-autonomous deficits of ASC which should systematically be considered when choosing the right cell source for tissue engineering-based stimulation of bone regeneration.

Long-term regeneration of cartilage defects treated with tissue engineering constructs often fails because of insufficient integration with the host tissue. We hypothesize that construct integration will be improved when implants actively interact with and integrate into the subchondral bone. Growth and Differentiation Factor 5 (GDF-5) is known to support maturation of chondrocytes and to enhance chondrogenic differentiation and hypertrophy of mesenchymal stromal cells (MSC). Therefore, we investigated whether GDF-5 is capable to stimulate endochondral ossification of MSC in vitro and in vivo and would, thus, be a promising candidate for augmenting fibrin glue in order to support integration of tissue engineering constructs into the subchondral bone plate.

To evaluate the adhesive strength of fibrin glue versus BioGlue^®, a commercially available glue used in vascular surgery, an ex vivo cadaver study was performed and adhesion strength was measured via pull-out testing. MSC were suspended in fibrin glue and cultivated in chondrogenic medium with and without 150 ng/mL GDF-5. After 4 weeks, the formed cartilage was evaluated and half of the constructs were implanted subcutaneously into immunodeficient mice. Endochondral ossification was evaluated after 2 and 4 weeks histologically and by microCT analysis. BioGlue^®and GDF-5-augmented fibrin glue were tested for 4 weeks in a minipig cartilage defect model to assess their orthotopic biocompatibility.

Pull-out testing revealed sufficient adhesive strength of fibrin glue to fix polymeric CellCoTec constructs in 6 mm cartilage defects, however, BioGlue^®showed significantly higher adhesive power. In vitro chondrogenesis of MSC under GDF-5 treatment resulted in equal GAG deposition and COLIIa1 and ACAN gene expression compared to controls. Importantly, significantly increased ALP-activity under treatment with GDF-5 on day 28 indicated enhanced hypertrophic differentiation compared to controls. In vivo, MSC-fibrin constructs pre-cultured with GDF-5 developed a significantly higher bone volume on day 14 and 28 compared to controls. When pre-cultured with GDF-5 constructs showed furthermore a significantly higher bone compactness (bone surface/bone volume coefficient) than controls, and thus revealed a higher maturity of the formed bone at 2 weeks and 4 weeks. Orthotopic biocompatibility testing in minipigs showed good defect filling and no adverse reactions of the subchondral bone plate for defects treated with GDF-5-augmented fibrin glue. Defects treated with BioGlue^®, however, showed considerable subchondral bone lysis.

Thus, BioGlue^®– despite its adhesive strength – should not be used for construct fixation in cartilage defects. GDF-5-augmented fibrin glue is considered promising, because of a combination of the adhesive strength of fibrin with an enhanced osteochondral activity of GDF-5 on MSC. Next step is to perform a large animal study to unravel whether GDF-5 stimulated endochondral ossification can improve scaffold integration in an orthotopic cartilage defect model.