Background
The number of young patients seeking medical consultation for symptoms relating to osteoarthritis (OA) of the knee is increasing [
1]. This is thought to be due to a combination of factors [
2]. Longer life expectancy also means that the proportion of the population continuing physically demanding careers and sporting lifestyles into their fifth, sixth, and even seventh decades is increasing [
3]. In addition to these risks, there are rising levels of obesity and there is clear evidence that the risk of OA is increased with obesity [
4]. Allied to the increasing rates of OA are patient expectations that a return to previous levels of activity should be possible following injury or trauma.
Osteoarthritis is a dynamic and metabolically active disease that involves all tissue components of the joint: bone, cartilage, synovium, muscle, and ligament. The key pathological features are of articular cartilage softening, fibrillation, and then ulceration leading to sclerosis and eburnation of subchondral bone. Articular cartilage degradation leads to release of inflammatory mediators and further joint damage due to this inflammatory component, thus the frequent reference to 'degenerative arthritis' is incorrect. Subchondral cyst and osteophyte formation are later features [
5].
Patients with OA of the knee present with symptoms that include joint pain, swelling, stiffness, crepitus, loss of function, and reduced quality of life [
6]. The initial management of OA of the knee should be non-operative, however, these measures often provide only limited and temporary benefit. Not until these options have been exhausted should surgical options be explored. Non-operative strategies may include patient education, exercise, weight loss, bracing, analgesia, non-steroidal anti-inflammatory drugs (NSAIDs) and possibly intra-articular (IA) injections. Although many of these treatment methods are employed the evidence for their benefit is mixed.
Meta-analyses have shown the benefit of muscle strengthening and aerobic exercise in the management of OA [
7,
8] but have highlighted the importance of patient compliance. The medical benefits of weight loss for the obese patient are clear. While it seems logical that weight loss should also relieve the pain associated with OA the evidence that weight loss can delay or even reverse symptoms associated with OA of the knee remains mixed [
9]. There are studies that have shown bracing to be effective [
10]. Bracing aims to reduce the biomechanical load in the affected compartment of the knee, or improve symptoms by reducing perceived instability. Although potentially effective, bracing is poorly tolerated by patients due to discomfort or skin complications, such as blistering, and there is evidence that compliance with long-term bracing for orthopedic conditions is poor.
Analgesic regimes have been proven to effectively improve the pain associated with OA. Paracetamol is effective in reducing the pain associated with OA of the knee [
11] but less so than NSAIDs. Systemic non-steroidal anti-inflammatory drugs are however associated with an increased risk of side effects such as gastrointestinal disturbance.
Intra-articular corticosteroids are widely used to manage the symptoms of osteoarthritic joints. Several studies and a Cochrane Review have shown the treatment to be beneficial versus placebo in the knee, but that there is little evidence to show that this benefit lasts beyond 4 weeks [
12,
13]. The 2009 Cochrane review [
14] analyzed the evidence for hyaluronan (HA) and hylan derivatives for viscosupplementation of the knee. The authors concluded that these products were comparable in efficacy to systemic forms of active intervention but with more local reactions and fewer systemic adverse events. The HA products have a more prolonged effect than IA corticosteroids. The numerous different HA preparations and administration regimes make a comparison of cost with corticosteroid difficult, but the raw cost of the HA is significantly more expensive than corticosteroid. Infection following joint injection is a rare but recognized complication and there is evidence of a higher risk of joint infection following TKR in patients who have had IA corticosteroid treatment. This makes some surgeons wary of offering IA injections to patients who may be a candidate for future joint replacement surgery.
Older patients with OA of the knee are successfully managed with TKR. These have been implanted in one form or another for over 50 years [
15]. Over time both prostheses and surgical techniques have evolved [
16] such that 15-year survival rates of up to 98% have been reported in older populations [
17]. For young people who may have a long life expectancy the concern is that the longevity of the prosthesis does not match that of the patient and complex revision surgery will be inevitable. The longer life expectancy of younger patients may be compounded by higher demand resulting in lower implant survival rates. Julin
et al. [
18] reported on the survival rates of TKR between different age groups from the Finnish Arthroplasty Register. Follow-up of 32,019 patients showed that 5-year survival rates were 92% and 95% in patients aged ≤ 55 and 56 to 65 years, respectively, compared to 97% in patients who were > 65 years of age (
P < 0.001). These differences remained statistically different once differences in implant and fixation type, sex, and diagnosis were adjusted for. W-Dahl
et al. [
19] similarly interrogated the Swedish Register and found a 10-year cumulative revision rate for patients younger than 55 years of age of 9%. Odland
et al. [
20] report 10-year outcomes from a cohort of 59 active patients (67 knees) of 55 years or younger. A total of 65% of patients were still performing moderate labor or sport activities but 16% had undergone revision for wear and/or osteolysis.
In addition to the issues of implant survival and complexity of future revision surgery, function after TKR may be a concern for younger and more active patients. Most surgeons advise against high-impact activities following TKR, which precludes patients from participating in a wide range of sports. The list of activities 'not recommended' by surgeons after TKR according to Knee Society surveys in 1999 and 2005 is decreasing [
21] and there is a paucity of evidence to guide patient advice about sporting activities after this procedure. There are small-scale series published of patients returning to high-level tennis [
22] and golf [
23] but these are in very select patient groups. The principle behind the advice given to patients to avoid high-impact activities is that implant wear is related to joint use not duration of implantation [
24].
Regardless of etiology the aims of surgical treatment for early OA remain the same: to provide pain relief and enable a return to a high level of function. Additionally, when considering surgical treatment options the ability to perform further surgery if disease progresses or implants fail should be taken into account.
We will discuss the surgical options available to treat OA of the knee in young adults. Defining 'young' in this context is not simple and will clearly depend on both the patient's chronological and biological age, however, for the purposes of this discussion we consider patients less than 55 years of age.
Historically, other than TKR the main surgical options for these patients were considered to be osteotomy or unicompartmental tibio-femoral knee replacement (UKR). However, advances in arthroscopic techniques and biologic treatments have opened up other potential avenues, as have patella-femoral joint (PFJ) replacements. We will discuss these treatments separately and consider the relative benefits and potential risks of each.
Summary
The management of the young patient with an osteoarthritic knee remains a significant challenge for the orthopedic surgeon. Multiple non-surgical treatments are available, but are unlikely to offer a lasting improvement in symptoms. We believe that with careful interrogation of patient's symptoms and a thorough examination it is usually possible to identify those osteoarthritic knees with coexisting pathology amenable to arthroscopic treatment, leading to an improvement in symptoms and delay of more invasive surgery.
Once these options are exhausted, the main choice is between HTO, UKR or TKR. While TKR remains an option that must be considered in the young patient the reduced longevity and higher expectations in this group allied to potential bone loss associated with a failed TKR mean that whenever possible we prefer to consider the options of HTO or UKR. Which option is most suitable depends upon patient characteristics and expectations.
In our practice, young, active and heavier males tend to be offered HTO. In young patients who fall outside this group our experience is that unicompartmental knee replacement is a successful procedure and we have had success revising these implants to TKR.
Autologous chondrocyte implantation and other techniques of 'biological' joint replacement are exciting treatment prospects for the future but are not currently supported by evidence.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
Both EH and PS were responsible for drafting and revising the manuscript. Both authors have read and approved the manuscript for publication.