It seems that the above scoring systems are not sensitive enough to depict symptoms and problems from the patellofemoral joint of a TKA. This is also a critical disadvantage due to the fact that anterior knee pain and patellofemoral dysfunction are challenging problems after TKA [52]. To the best of our knowledge only few studies present and use specific patellofemoral rating systems [53–55]. The Feller score allocates 30 points for anterior knee pain and 10 points for each of quadriceps strength, ability to rise from a chair and stair climbing [53]. The Kujala score is a scoring questionnaire for anterior knee pain. It allocates points for limping (5), support (5), walking (5), climbing stairs (10), squatting (5), running (10), jumping (10), prolonged sitting with the knees flexed (10), pain(10), swelling (10), abnormal painful patellar movements (subluxations) (10), atrophy of the thigh (5) and flexion deficiency (5), with the maximal sum score being 100 [54]. The patella score presented by the Bristol group allocates points anterior knee pain (2), pain climbing stairs (2), patella tenderness (2), patella crepitus (2) and radiological appearance of patella instability (2) [55]. Recently, a novel outcome measure, the Samsung Medical Center (SMS) patellofemoral scoring system has been published, with emphasis on the evaluation of patellofemoral joint status [52]. It evaluates separately patellofemoral pain and function and then consider them in combination. It lacks items such as limping, swelling, atrophy of the thigh and flexion deficiency that are not specific for patellofemoral problems.

Another outcome measure that is widely used in recent literature is survival analysis of TKAs. Survival analysis is defined as a set of methods for analyzing data where the outcome variable is the time until the occurrence of an event of interest e.g. failure of the joint arthroplasty. Survival analysis techniques can be classified into nonparametric (Kaplan Meier product limit method), parametric (exponential methods) and semi-parametric method (Cox-proportional method). The survivorship rate is the percentage of TKAs which have not been revised in any given series of patients for any reason. Generally, it is considered the most often used measure in the literature. It is the most important measure when considering differences between various prosthetic designs. Lastly, it is adjuvant when answering the most difficult patient question, “How long will the knee last”. Survival rate depends as well as on patient related factors (body weight, activity) as well as on implant (condylar, unicompartment, posterior cruciate retaining model, posterior stabilized etc.) and surgeon (technique) related factors.

Patients and doctors do not always agree on what constitutes a good postoperative result [56]. For this reason the use of patient reported outcome measures (PROMS) is increasing. PROMS assess the result of TKA from the patient’s point of view only [57]. They can be used to evaluate the quality of care delivered by the providers of elective procedures, benchmark their performance and assess the efficacy and cost effectiveness of different approaches and provide a baseline for peer comparison between institutions [57]. Using PROMS, clinicians could achieve best outcomes and improve standards [58]. PROMS are using outcome scores like Oxford Knee Score which has previously been proven to be a reliable, valid outcome score and it is recommended for assessment of large TKA [59]. They also collect information on the effectiveness of care delivered to NHS patients as perceived by the patients themselves. The data adds to the wealth of information available on the care delivered to NHS funded patients to complement existing information on the quality of services [60].

Outcome scoring is vital in the accurate evaluation of TKA. There has been a paradigm shift in the determinants of success over the last two decades, from those based on physical examination and radiographic variables (objective data) to a more patient – centred (subjective data) assessment of outcome [5]. Modern knee surgery has allowed patients’ expectations and activity levels to increase but it remains difficult to accurately assess outcome. Evidence in the current literature confirms that few scoring systems have satisfactory levels of reliability and validity [5].

What is clear is that those systems which employ a high degree of patient involvement, such as the Oxford-12 score perform better as a patient-based assessment tool. The generic instruments have a greater potential to measure side-effects or unforeseen effects of treatment, and the WOMAC in particular remains a valid, reliable and responsive measure. However, it is not possible to recommend a single best knee scoring system. Indeed, the ideal of a short, easy to administer, reliable and valid global knee questionnaire does not currently exist.