Postmeniscectomy osteonecrosis of the knee: A case report and literature review

Postarthroscopic osteonecrosis of the knee (PAONK) is a rare form of osteonecrosis for which the pathogenesis and etiology remain poorly understood; however, there is evidence of a close association with meniscectomy in most PAONK cases. Based on this evidence, postmeniscectomy osteonecrosis of the knee (PMONK) has been suggested as a new category. As early diagnosis and appropriate treatment can improve prognosis, there is a need to differentiate PMONK from spontaneous osteonecrosis of the knee (SONK). This differentiation is specifically important in the Middle East and Arab countries where PMONK and PAONK have not been reported before, which could have resulted from under-reporting or under-diagnosis. To address this gap, we present a case of PMONK from this region and discuss assessment findings and treatment relative to the current evidence.

A Retrospective Study of Unicompartmental Knee Arthroplasty Functional Outcome and the Incidence of Medial Meniscus Posterior Root Tear in Spontaneous Osteonecrosis of the Knee

Background. Spontaneous osteonecrosis of the knee (SONK) can lead to severe knee osteoarthritis predominantly localized to the medial compartment. We aimed to determine whether unicompartmental knee arthroplasty was an effective treatment for primary SONK. Methods. We analyzed the functional outcomes in 23 patients with SONK (with a magnetic resonance imaging- (MRI-) confirmed diagnosis) who underwent UKA at a single center. The mean follow-up time was 67 months post-UKA. Results. Significant improvements in function were indicated by reduced Oxford Knee and Visual Analogue Scale scores after UKA, and there were no specific complications after the procedures. The incidence of MRI-identified medial meniscus posterior root tear (MMPRT) was 69.6% (16/23). Conclusion. Unicompartmental arthroplasty for SONK is less destructive to the native knee structure than total knee arthroplasty but can achieve comparable prognosis with strict patient selection. While the precise etiology of SONK is unknown, one theory posits that a MMPRT may change the biomechanical circumstances of the knee joint, leading to osteonecrosis. Although not confirmatory, the high prevalence rate suggests that MMPRT may have a key role in the development of SONK. UKA is an effective treatment option for SONK, resulting in significant functional improvement. Long-term (>10 years) outcomes should be investigated.

Spontaneous Osteonecrosis of the Knee: a Systematic Review of Conservative Treatment Approaches

Background: Spontaneous osteonecrosis of the knee (SONK) is an insufficiently defined disease. Although recent research suggests that SONK may be caused by subchondral insufficiency fractures, its precise etiology remains unclear. Currently, no therapeutic guidelines exist.Purpose: This systematic review aimed to collate the scientific literature on conservative treatment approaches for SONK and to derive respective recommendations.Methods: The PUBMED database was searched for relevant articles published until November 2020. All articles in German or English language dealing with the conservative therapy of SONK were included. Animal research studies and reviews were not considered. Studies that used specific treatment outcomes as inclusion criterion and those that lacked a conservative treatment group, magnetic resonance imaging-based diagnosis, reported outcomes of conservatively managed patients or basic descriptions of the treatment modalities were excluded.Results: Twenty-two articles comprising a total sample size of 521 patients were included. Eighteen of the included studies (82%) tested the effects of some form of restriction of weight-bearing, bisphosphonates or a combination of both. Sixteen studies (73%) reported clinical and/or radiological improvements. However, outcomes varied considerably in dependency of the radiologic presentation, demography and further prognostic factors.Conclusion: Many conservative therapy methods appear effective in the treatment of orthopedic syndromes classified as SONK, with the most robust evidence existing for restriction of weight-bearing and bisphosphonates. The heterogeneity of radiologic presentations and treatment outcomes suggests that the generic term SONK might obscure the presence of different underlying pathologies. Indeed, many lesions may represent subchondral fractures, which should be referred to as subchondral fractures of the knee (SFK). A clear delineation of the disorders and standardized MRI-based diagnostic criteria are required.

A Retrospective Review of Unicompartmental Knee Arthroplasty Functional Outcome and the Incidence of Medial Meniscus Posterior Root Tear in Spontaneous Osteonecrosis of the Knee

Background:Spontaneous osteonecrosis of the knee (SONK) can lead to severe knee osteoarthritis predominantly localized to the medial compartment. We aimed to determine whether unicompartmental knee arthroplasty was an effective treatment for primary SONK.Methods: We analyzed the functional outcomes in 23 patients with SONK (with a magnetic resonance imaging [MRI]-confirmed diagnosis) who underwent UKA at a single center. The mean follow-up time was 67 months post-UKA.Results: Significant improvements in function were indicated by reduced Oxford Knee and Visual Analogue Scale scores after UKA, and there were no specific complications after the procedures. The incidence of MRI-identified medial meniscus posterior root tear (MMPRT) was 69.6% (16/23).Conclusion: Unicompartmental arthroplasty for SONK is less destructive to the native knee structure than total knee arthroplasty, but can achieve comparable prognosis with strict patient selection. While the precise etiology of SONK is unknown, one theory posits that a MMPRT may change the biomechanical circumstances of the knee joint, leading to osteonecrosis. Although not confirmatory, the high prevalence rate suggests that MMPRT may have a key role in the development of SONK. UKA is an effective treatment option for SONK, resulting in significant functional improvement. Long-term (>10 years) outcomes should be investigated.

A Retrospective Review of Unicompartmental Knee Arthroplasty Functional Outcome and the Incidence of Medial Meniscus Posterior Root Tear in Spontaneous Osteonecrosis of the Knee

Background:Spontaneous osteonecrosis of the knee (SONK) can lead to severe knee osteoarthritis predominantly localized to the medial compartment. We aimed to determine whether unicompartmental knee arthroplasty was an effective treatment for primary SONK.Methods:We analyzed the functional outcomes in 23 patients with SONK (with a magnetic resonance imaging [MRI]-confirmed diagnosis) who underwent UKA at a single center. The mean follow-up time was 67 months post-UKA.Results:Significant improvements in function were indicated by reduced Oxford Knee and Visual Analogue Scale scores after UKA, and there were no specific complications after the procedures. The incidence of MRI-identified medial meniscus posterior root tear (MMPRT) was 69.6% (16/23).Conclusion:Unicompartmental arthroplasty for SONK is less destructive to the native knee structure than total knee arthroplasty, but can achieve comparable prognosis with strict patient selection. While the precise etiology of SONK is unknown, one theory posits that a MMPRT may change the biomechanical circumstances of the knee joint, leading to osteonecrosis. Although not confirmatory, the high prevalence rate suggests that MMPRT may have a key role in the development of SONK. UKA is an effective treatment option for SONK, resulting in significant functional improvement. Long-term (>10 years) outcomes should be investigated.

Osteonecrosis of the Femoral Medial Condyle Due to Leg Length Discrepancy After A Traffic Accident

Untreated leg length discrepancy can cause spontaneous osteonecrosis of the knee, which is associated with subchondral insufficiency fractures of the knee and progression or onset of osteoarthritis of the knee. Spontaneous osteonecrosis of the knee can be secondary to cartilage loss or additional subchondral changes. A 40-year-old female underwent opening-wedge high tibial osteotomy and osteochondral grafting for osteonecrosis of the femoral medial condyle and osteoarthritis of the knee caused by leg length discrepancy after a traffic accident. High tibial osteotomy and cartilage restoration are often considered for the treatment of knee osteonecrosis with cartilage damage in younger patients.