O tecido muscular esquelético possui a maior massa do corpo humano, correspondendo a 45% do peso total. As lesões musculares podem ser causadas por contusões, estiramentos ou lacerações. A atual classificação separa as lesões entre leves, moderadas e graves. Os sinais e sintomas das lesões grau I são edema e desconforto; grau II, perda de função, gap e equimose eventual; grau III, rotura completa, dor intensa e hematoma extenso. O diagnóstico pode ser confirmado por ultrassom (dinâmico e barato, porém examinador-dependente); e ressonância magnética (RM) (maior definição anatômica). A fase inicial do tratamento se resume à proteção, ao repouso, ao uso otimizado do membro afetado e crioterapia. Anti-inflamatórios não hormonais (AINHs), ultrassom terapêutico, fortalecimento e alongamento após a fase inicial e amplitudes de movimento sem dor são utilizados no tratamento clínico. Já o cirúrgico possui indicações precisas: drenagem do hematoma, reinserção e reforço musculotendíneos. Não houve suporte financeiro de fontes públicas, comerciais, ou sem fins lucrativos. ^* Trabalho realizado no Laboratório de Investigação Médica do Sistema Musculoesquelético - LIM41 do Departamento de Ortopedia e Traumatologia da FMUSP, Grupo de Medicina do Esporte do Instituto de Ortopedia e Traumatologia (IOT) do Hospital das Clínicas da FMUSP e Centro de Excelência Médica da FIFA. Received: 06 October 2020 Accepted: 08 March 2021 Article published online: 20 January 2022 © 2022. Sociedade Brasileira de Ortopedia e Traumatologia. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commecial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua do Matoso 170, Rio de Janeiro, RJ, CEP 20270-135, Brazil

Background: A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSC), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts are a predictable source for the treatment of cartilage injuries. This manuscript presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and pre-clinical large animal model. Experiment: In this controlled experimental study with fourteen miniature pigs, a scaffold-free Tissue Engineering Construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging using the 3D-DESS sequence, and compositional assessment was carried out based on T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, submitted to standard histological processing, sectioned, and stained with hematoxylin & eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of the Young’s modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a Finite Element model was used to simulate and characterize properties of the osteochondral block. Results: At six months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. Conclusions: The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after six months of follow-up in a large animal model for articular cartilage restoration.