Posttraumatic arthritis is one of the most frequent causes of disability following joint trauma. The objective of this study was to develop a model of a closed articular fracture in the mouse knee joint to quantify the temporal sequence of joint degeneration in a model of posttraumatic arthritis. Closed intraarticular fractures were created in the tibial plateau of adult mice (C57BL/6) using a computer-controlled materials testing system and a custom-built indenter tip. Tibial plateau fractures were classified and imaged over time using high-resolution digital radiography. Animals were sacrificed at 2, 4, 8, and 50 weeks following fracture, and the experimental and contralateral control limbs were harvested for histology and micro-computed tomography (microCT) analysis. By radiographic analysis, tibial plateau fractures closely resembled clinical fractures. More complex and comminuted fractures correlated to significantly higher fracture energies. Histologic analysis demonstrated progressive joint degeneration as measured by a modified Mankin scale, with fibrillation and loss of proteoglycan in the articular cartilage. Subchondral bone thickening was also observed in experimental joints. The induction of a closed intraarticular fracture of the mouse tibial plateau generated a reproducible and clinically relevant joint injury that progressed to osteoarthritis-like changes by histologic and microCT evaluations. The ability to induce joint degeneration without an osteotomy or open arthrotomy provides a valuable new model for studying the natural sequelae of posttraumatic arthritis. Notably, the use of a murine model will facilitate the use of genetically modified animals for the investigation of specific genes implicated in the pathology of posttraumatic arthritis. ß

Objective. Posttraumatic arthritis is a frequent long-term complication of intraarticular fractures. A model of a closed intraarticular fracture in C57BL/6 mice that progresses to posttraumatic arthritis has been developed. The MRL/MpJ mouse has shown unique regenerative abilities in response to injury. The objective of this study was to determine if the MRL/MpJ mouse is protected from posttraumatic arthritis after intraarticular fractures.Methods. Intraarticular fractures were created in MRL/MpJ mice and C57BL/6 control mice (n ‫؍‬ 16 each). Limbs were analyzed for posttraumatic arthritis 4 and 8 weeks after fracture using microfocal computed tomography bone morphology, subchondral bone thickness evaluation, and histologic evaluation of cartilage degeneration. Serum cytokines and biomarkers were measured after the mice were killed.Results. Intraarticular fractures were successfully created in all 32 mice. In the experimental fractured limbs, C57BL/6 mice had a decrease in bone density, increased subchondral bone thickness, and increased cartilage degeneration compared with normal contralateral control limbs. In the MRL/MpJ mice, no differences in bone density, subchondral bone thickness, or histologic grading of cartilage degeneration were seen between fractured and contralateral control limbs. Cytokine analysis showed lower systemic levels of the proinflammatory cytokine interleukin-1␣ (IL-1␣) and higher levels of the antiinflammatory cytokines IL-4 and IL-10 in the MRL/MpJ mice.Conclusion. This study shows that the MRL/MpJ mouse is relatively protected from posttraumatic arthritis after intraarticular fracture. Further investigation into the mechanism involved in this response will hopefully provide new insight into the pathogenesis, prevention, and treatment of posttraumatic arthritis after intraarticular fracture.

Post-traumatic arthritis is a frequent consequence of articular fracture. The mechanisms leading to its development after such injuries have not been clearly delineated. A potential contributing factor is decreased viability of the articular chondrocytes. The object of this study was to characterise the regional variation in the viability of chondrocytes following joint trauma. A total of 29 osteochondral fragments from traumatic injuries to joints that could not be used in articular reconstruction were analysed for cell viability using the fluorescence live/dead assay and for apoptosis employing the TUNEL assay, and compared with cadaver control fragments. Chondrocyte death and apoptosis were significantly greater along the edge of the fracture and in the superficial zone of the osteochondral fragments. The middle and deep zones demonstrated significantly higher viability of the chondrocytes. These findings indicate the presence of both necrotic and apoptotic chondrocytes after joint injury and may provide further insight into the role of chondrocyte death in post-traumatic arthritis.

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Knee arthroscopy is an important diagnostic and therapeutic tool in the management of disorders of the knee. In a series of 4 articles, the basics of knee arthroscopy are reviewed. In this article (part 2), surface anatomy and the anterolateral and anteromedial portals are reviewed. Accurate portal placement is critical to both diagnostic and operative arthroscopy. Mastery of the surface anatomy allows accurate and reproducible portal placement. K nee arthroscopy is the most commonly performed orthopaedic procedure. Indications include diagnostic arthroscopy, meniscectomy, loose body removal, chondroplasty, microfracture, irrigation and debridement, and ligament reconstruction. In this series of articles, we present a comprehensive review of the complete surgical technique for basic knee arthroscopy.

Knee arthroscopy is an important diagnostic and therapeutic tool in the management of disorders of the knee. In a series of 4 articles, the basics of knee arthroscopy are reviewed. In this article (part 3), step-by-step diagnostic arthroscopy is reviewed. Diagnostic arthroscopy is a crucial skill for diagnosing intra-articular disorders of the knee including meniscal, synovial, ligamentous, and articular cartilage pathology. Mastery of the basic diagnostic arthroscopy is a critical tool for orthopaedic surgeons treating disorders of the knee. K nee arthroscopy is the most commonly performed orthopaedic procedure. Indications include diagnostic arthroscopy, meniscectomy, loose body removal, chondroplasty, microfracture, irrigation and debridement, and ligament reconstruction. In this series of articles, we present a comprehensive review of the stepby-step surgical technique for basic knee arthroscopy.

Knee arthroscopy is an important diagnostic and therapeutic tool in the management of disorders of the knee. In a series of 4 articles, the basics of knee arthroscopy are reviewed. In this article (part 4), the basics of operative knee arthroscopy are reviewed including chondroplasty and meniscectomy. Evaluation of the cruciate ligaments is also reviewed. Mastery of these techniques is critical for the treatment of the most common pathology encountered during knee arthroscopy. K nee arthroscopy is the most commonly performed orthopaedic procedure. Indications include diagnostic arthroscopy, meniscectomy, loose body removal, chondroplasty, microfracture, irrigation and debridement, and ligament reconstruction. In this series of articles, we present a comprehensive review of the complete surgical technique for basic knee arthroscopy.