To date, there is a paucity of studies reporting the outcomes of patients over the age of 40 years with PCL reconstruction. In our study, knee stability was restored in all patients aged 40 years or older with failed conservative treatment after receiving PCL reconstruction. In our series, patients receiving PCL reconstruction surgery showed significant improvements in the IKDC score, Lysholm score, and Tegner activity level, while surgery did not increase the risk of knee arthritis deterioration. No major complications were noted with a minimum follow-up time of 2 years. Approximately half of the patients returned to activities at their preinjury level.
Several studies on conservative treatment for isolated PCL injury have reported good subject and functional outcomes [1,2,3], but the mean age of the patients in these studies ranged from 22 to 31 years. There is a paucity of research focusing on conservative treatment for older patients with PCL injury, and age-related alterations in the ligament healing process, such as decreased healing potential, the declining function of mesenchymal stem cells, and decreased structural organization with age should considered. Stolzing et al.  found that the quality and quantity of human mesenchymal stem cells (hMSCs), which contribute to regeneration of various connective tissues, significantly decrease with age. However, more evidence is still needed to verify whether these age-related alterations in elderly patients result in poorer clinical and functional outcomes than observed in younger patients with PCL injuries treated nonoperatively.
With improvements in anesthesia, surgical techniques, instrumentation, and rehabilitation programs, surgeons should re-evaluate the benefits of surgical intervention in patients and adjust the indications for surgery according to recent evidence-based studies. In the present study, patient-reported outcome improvements were noted in the IKDC score (from 46.5 preoperatively to 79.0 postoperatively), Lysholm score (from 65.5 to 88.3), and Tegner activity score (from 2.3 to 4.0). Similar results were reported in previous studies that did not conduct age-subgroup analyses [7,8,9,10,11,12,13, 22]. A study by Belk et al.  that included a total of 132 patients with a mean age at the time of surgery of 31.6 years undergoing PCL reconstruction with autograft reported that patients achieved an improvement of 20 in the IKDC score, 22.7 improvement in the Lysholm score, and 3.9 improvement in the Tegner activity score. Comparing the results of these studies, it may be concluded that older patients with PCL injury can receive the same benefits from operative therapy that younger patients enjoy.
In our study, approximately half (51.2%) of the patients were able to return to activities at their preinjury level. This result is lower than those of previous studies that included patients younger in age or highly active athletes. Rauck et al.  reported a high rate (79%) of return to sport, overall patient satisfaction, and restoration of function, with good functional scores, after PCL reconstruction in 14 athletes with a mean age of 27.5 years (range 17–43). A study by Song et al.  enrolled 36 patients with a mean age of 37 years that received the transtibial technique and 30 patients with a mean age of 35 years that received tibial inlay PCL reconstruction. In their study, 21 patients (58.3%) in the transtibial group and 19 patients (63.3%) in the tibial inlay group were able to return to preinjury levels of sports activity. However, Devitt et al.  reviewed a combined 14 studies that reported on 523 patients with a mean age of 30.2 years and that received isolated PCL reconstruction. The results revealed a significant improvement in functional outcome scores, but a low rate (44% (95% CI, 23%-66%)) of return to preinjury level among the pooled patients. These findings provide essential information when counseling patients about realistic expectations prior to surgical intervention.
Although numerous studies have reported that nonoperative treatment of PCL injury is associated with an increased incidence of degenerative arthritis [4, 5], whether undergoing PCL reconstruction will prevent osteoarthritis progression compared with nonoperative treatment is still unknown. In this study, arthroscopic findings showed that 97.7% of patients had osteochondral lesions, and 18 (43.9%) patients showed stage I degenerative changes according to the Ahlbäck classification at the time of the preoperative radiographic study. There were no cases of osteoarthritis deterioration among these stage I osteoarthritis patients, but 5 (12.2%) patients without osteoarthritis had developed up to stage I degenerative changes at the last postoperative visit. This was also noted in most previous studies, and thus, it is difficult to distinguish whether the osteoarthritis was due to the initial trauma or to surgical intervention . Hence, further high-quality randomized controlled trials focusing on comparing the incidence of osteoarthritis degeneration between patients treated with surgical reconstruction and those treated with conservative therapy are needed.
In our study, 48.8% of patients had associated meniscal lesion and half of these patients suffered from medial side tear during arthroscopic examination. This could partially explain limitation of extreme flexion (73.2% of patients) and extension (19.5% of patients) before operation, and range of motion improved greatly after meniscal tear being treated with either partial meniscectomy or meniscal repair. Zhang et al.  reported PCL injury resulted in radial displacement of the medial meniscus which may lead to degenerative changes of meniscus. A study by Gao et al.  revealed human cadaveric knee with PCL transection had a higher strain on whole medial meniscus. Pearsall et al.  reported meniscal strain increased in PCL injured knee and decreased after PCL reconstruction. According to these studies, early intervention with PCL reconstruction plays an important role in reducing meniscal strain and subsequent degeneration.
There has been increasing recognition that the health status, type and level of activity of the older population have changed significantly in many parts of the world over the past few decades. This has led to the development of alternative concepts to offer more comprehensive management when surgeons perform preoperative assessments. Physiological age is more important than chronological age in PCL-deficient patients. To provide appropriate treatment, surgeons should take patients’ expectations, lifestyle, and activity level before injury into consideration.
The limitations of this study include the absence of a control group, the small number of patients, the short observation period, and the lack of objective information on KT-1000 arthrometer and stress radiographs compared with the healthy side. Further studies with a comparison between young and older patients are needed to clarify the clinical and functional outcomes of PCL reconstruction in different age groups. Additionally, this is a retrospective study with heterogeneous surgical techniques. A longer follow-up period is required to observe the incidence of later complications or further arthritis deterioration. Lastly, the patients underwent conservative treatment before surgery. Although it failed, there is a possibility that conservative treatment contributed part of the results. Nonetheless, subsequent operative intervention after failed non-operative management is in line with current treatment strategy for PCL injury.