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Elizaveta Kon, Matej Drobnic, Phil A. Davidson, Andrew Levy, Ken Zaslav and Dror Robinson

Osteochondral defects are often symptomatic and lead to deranged joint function. The spontaneous healing capacity of osteochondral defects is limited. In this case study, use of an acellular scaffold capable of induction of mesenchymal stem-cell migration is described. This scaffold was used on an Outerbridge grade IV medical condylar defect measuring ~2 cm2. At 24 mo follow-up, the articular surface appeared restored by MRI, and the patient returned to sports.

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Erik A. Wikstrom, Kyeongtak Song, Kimmery Migel and Chris J. Hass

Key Points ▸ Aberrant loading is a mechanism which negatively impacts cartilage health. ▸ Individuals with CAI demonstrate higher normalized loading rate and less time to peak vGRF compared to controls. ▸ Altered loading rates in CAI may lead to an increased risk of early cartilage degeneration

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Emily E. Kruithof, Spencer A. Thomas and Patricia Tripp

be considered with postsurgical rehabilitation. Osteochondritis dissecans (OCD) is a condition in which damage occurs to subchondral bone with possible secondary damage to the overlying articular cartilage. Patients with stable OCD of the knee often report an aching feeling or activity-related pain

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Michael Ra, Michael Sitler, Jeff Ryan, Raymond Moyer, Paul Marchetto, John Kelly and Iris Kimura

Chondral lesions often occur in the knee as isolated defects or part of more complex injuries. Articular cartilage defects decrease the ability of the knee to sustain weight-bearing loads and may accelerate degeneration of the joint when left untreated. The purpose of this study was to determine the clinical, functional, and radiographic outcome of arthroscopic abrasion chondroplasty of the knee. The Articular Cartilage Rating System was used to assess the location, size, depth, and description of the articular lesion. The Standard Knee Evaluation Form and Cincinnati Knee Rating Scale were used to assess the clinical, functional, and radiographic outcome of the procedure. Average time to postsurgery follow-up was 46 ± 26.69 months. Within the constraints of the present study, arthroscopic abrasion chondroplasty of the knee had a favorable clinical, functional, and radiographic outcome. However, more study is needed with larger samples and longer follow-up before definitive conclusions about the efficacy of the procedure can be made.

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Leslie J. Low, Mary J. Knudsen and Claudine Sherrill

In recent years, the number of individuals with dwarfism participating in sports and physical activities has increased. The Dwarf Athletic Association of America (DAAA) has grown from 30 athletes in 1985 to over 600 in 1994. This paper details the structural, intellectual, motor, orthopedic, and medical characteristics of six types of dwarfism (achondroplasia, hypochon-droplasia, cartilage-hair hypoplasia, diastrophic dysplasia, spondyloepiphyseal dysplasia tarda, and spondyloepiphyseal dysplasia congenita) seen in individuals currently participating in eight DAAA-sanctioned sports. Implications and modifications for participation in physical activity, physical education, and sport are included.

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Jay R. Ebert and Peter K. Edwards

Autologous chondrocyte implantation (ACI) has demonstrated good clinical success in the repair of articular cartilage defects in the knee. Postoperative rehabilitation after ACI is considered critical in returning the patient to an optimal level of function by attempting to create the appropriate mechanical environment for cartilage regrowth, and it involves a progressive program that emphasizes full motion, progressive partial weight bearing (PWB), and controlled exercises. While evidence-based research is clearly lacking in all components of ACI rehabilitation, one important element in this treatment algorithm that has been subjected to some early scientific study is the gradual progression of the patient back to full weight-bearing (WB) gait after surgery. With the continual advancement of ACI surgical techniques, along with clinical experience and improved knowledge of histology and of the maturation process of chondrocytes, proposed postoperative WB protocols have evolved to better reflect the nature of the specific ACI surgery. The purpose of this article is to present the varied PWB programs that have been practiced alongside the evolving ACI surgical technique, the experimental basis for such protocols, the issues pertinent to the accurate prescription of WB, and future directions for developing such methods to best return patients to an optimal level of function after ACI.

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Robert E. Mangine and Timothy E. Kremchek

This article provides the basis for development of an evaluation-based protocol of the anterior cruciate ligament (ACL). The historical background for ACL protocols is reviewed, and the foundation for protocol development is described. Crucial to the design of a rehabilitation protocol are basic science components, including surgical technique, biomechanics of exercise application, soft tissue healing response, articular cartilage response to injury and surgery, and evaluation fundamentals. The evaluation-based protocol was designed to account for patient variation through a hierarchy approach to exercise and functional levels. To assess the effectiveness of this approach, data are provided that support this protocol format. The outcome data are consistent with data found in the literature. It is concluded that rehabilitation must revolve around intrinsic patient variables, rather than the extrinsic independent variables.

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Richard B. Souza, Shruti Arya, Christine D. Pollard, George Salem and Kornelia Kulig

The purpose of the current investigation was to test the hypothesis that subjects with patellar tendinopathy would demonstrate altered sagittal plane joint moment contributions during hopping tasks. Fourteen subjects (7 patellar tendinopathy, 7 controls) participated. Sagittal net joint moments of the lower extremity, total support moment, and joint contributions to the total support moment were calculated while subjects hopped continuously at a self-selected frequency and at 1.67 Hz. Significant differences were observed for contributions to the total support moment (p = .022). When averaged across hopping frequencies, subjects with patellar tendinopathy demonstrated greater hip contribution (p = .030) and lesser knee contribution (p = .006) compared with the control subjects. Shifting the workload away from the knee and toward the hip may result in a detrimental increase in hip demand and potentially harmful long-term effects on the articular cartilage of the hip.

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Benno M. Nigg, Gerald K. Cole and Gert-Peter Brüggemann

Impact forces have been speculated to be associated with the development of musculoskeletal injuries. However, several findings indicate that the concepts of “impact forces” and the paradigms of their “cushioning” may not be well understood in relation to the etiology of running injuries and that complex mechanisms may be responsible for injury development during running. The purposes of this paper are (a) to review impact mechanics during locomotion, (b) to review injuries and changes of biological tissue due to impact loading, and (c) to synthesize the mechanical and biological findings. In addition, directions for future research are discussed. Future research should address the development of noninvasive techniques to assess changes in the morphology and biochemistry of bone, cartilage, tendon, and ligaments; researchers should also try to simulate impact loading during activities such as running, focusing on the interaction of the various loading parameters that determine the acceptable windows of loading for biological tissues.

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Peter K. Edwards, Jay R. Ebert, Gregory C. Janes, David Wood, Michael Fallon and Timothy Ackland


Matrix-induced autologous chondrocyte implantation (MACI) has become an established technique for the repair of chondral defects in the knee. MACI has traditionally required an open arthrotomy, but now lends itself to an arthroscopic technique, which may decrease the associated comorbidity of arthrotomy, potentially allowing for faster rehabilitation.


To compare postoperative outcomes between arthroscopic and open arthrotomy techniques of MACI and present a case for faster recovery and accelerated rehabilitation after surgery.


Retrospective cohort study.


Private functional rehabilitation facility.


78 patients (41 arthroscopic, 37 open) treated with MACI for full-thickness cartilage defects to the femoral condyles.


According to surgeon preference, patients recruited over the same time period underwent MACI performed arthroscopically or via a conventional open arthrotomy. Both surgical groups were subjected to an identical rehabilitation protocol.

Main Outcome Measures:

Patient-reported (Knee Injury and Osteoarthritis Outcome Score, Short Form Health Survey, and visual analogue scale) and functional (6-min-walk test, 3-repetition straight-leg-raise test [3R-SLR]) outcomes were compared presurgery and at 3, 6, and 12 mo postsurgery. Active knee range of motion (ROM) was additionally assessed 4 and 8 wk postsurgery. MRI evaluation was assessed using magnetic-resonance observation of cartilage-repair tissue (MOCART) scores at 3 and 12 mo. The length of hospital stay was evaluated, while postsurgery complications were documented.


Significant improvements (P < .05) for both groups were observed over the 12-mo period for patient-reported and functional outcomes; however, the arthroscopic cohort performed significantly better (P < .05) in active knee-flexion and -extension ROM and the 3R-SLR. No differences were observed in MOCART scores between the 2 groups at 12 mo. Patients who received arthroscopic implantation required a significantly reduced (P < .001) hospital stay and experienced fewer postoperative complications.


Arthroscopic MACI in combination with “best practice” rehabilitation has shown encouraging early results, with good clinical outcomes to 12 mo, reduced length of patient hospitalization, and reduced risk of postsurgery complications. This may have important implications for postoperative rehabilitation and a faster return to full function.