It is a not so uncommon clinical scenario: well-fixed, well-aligned, balanced total knee arthroplasty with continued pain. However, radiographs also demonstrate an unresurfaced patella. The debate continues and the controversy remains as whether or not to routinely resurface the patella in total knee arthroplasty. In perhaps the most widely referenced article on the topic, the overall revision rates were no different between the resurfaced (9%) and the unresurfaced (12%) groups and thus their conclusion was that similar results can be obtained with and without resurfacing. However, a deeper look in to the data in this study shows that 4 times more knees in the unresurfaced group were revised for patellofemoral problems. A more recent study concluded that selectively not resurfacing the patella provided similar results when compared to routinely resurfacing. The study does emphasise however, that this conclusion depends greatly on femoral component design and operative diagnoses. This suggests that selective resurfacing with a so-called “patella friendly” femoral component in cases of tibio-femoral osteoarthritis, is a safe and effective strategy. Finally, registry data would support routine resurfacing with a 2.3 times higher relative risk of revision seen in the unresurfaced TKA. Regardless of which side of the debate one lies, the not so uncommon clinical scenario remains; what do we do with the painful TKA with an unresurfaced patella. Precise and accurate diagnosis of the etiology of a painful TKA can be very difficult, and there is likely a strong bias towards early revision with secondary patellar resurfacing in the painful TKA with an unresurfaced TKA. At first glance, secondary resurfacing is associated with relatively poor outcomes. Correia, et al. reported that only half the patients underwent revision TKA with secondary resurfacing had resolution of their complaints. Similarly, only 53% of patients in another series were satisfied with the procedure and pain relief. The conclusions that can be drawn from these studies and others are that either routine patellar resurfacing should be performed in all TKA or, perhaps more importantly, we need to better understand the etiology of pain in an otherwise well-aligned, well-balanced, well-fixed TKA. It is this author's contingency that the presence of an unresurfaced patella leads surgeons to reoperate earlier, without truly identifying the etiology of pain or dissatisfaction. This strong bias; basically there is something more that can be done, therefore we should do it, is the same bias that leads to early revision of partial knee arthroplasty. While very difficult, we as knee surgeons should not revise a partial knee or secondarily resurface a patella due to pain or dissatisfaction. Doing so, unfortunately, only works about half the time. The diagnostic algorithm for evaluating the painful, uresurfaced TKA includes routinely ruling out infection with serum markers and an aspiration. Pre-arthroplasty radiographs should be obtained to confirm suitability and severity of disease for an arthroplasty. An intra-articular diagnostic injection with Marcaine +/− corticosteroid should provide significant pain relief. MARS MRI may be beneficial to evaluate edema within the patella. Lastly, operative implant stickers to confirm implant manufacturer and type are critical as some implants perform less favorably with unresurfaced patellae. To date, no studies of secondary resurfacing describe the results of this, or similar, algorithms for defining patellofemoral problems in the unresurfaced TKA and therefore it is still difficult to conclude that poor results are not simply due to our inherent bias towards early revision and secondary resurfacing of the unresurfaced patella

Whether or not to resurface the patella in total knee arthroplasty (TKA) remains controversial. Several methods of dealing with the patella exist: ALWAYS resurface; NEVER resurface; SOMETIMES resurface. There is good reason to consider selective patellar resurfacing. First, in an age of partial knee arthroplasty we have become more tuned in to analyzing patterns of arthritis. In TKA there is a high percentage of patients who do not have significant patellar cartilage wear or anterolateral knee pain. These patients may be candidates for leaving the patella unresurfaced in TKA. Arno et al found that 42% of patients had no significant patellar arthritis at the time of TKA. Roberts et al found that only 15% of patients should undergo patella resurfacing based on the presence of exposed bone on the patella; the other 85% could be considered suitable for leaving the patella unresurfaced. Second, despite a cumulative incidence of less than 5–10%, problems related to patellar resurfacing account for perhaps the most catastrophic complications encountered, with treatments that have limited success. These complications include fracture, avascular necrosis, extensor mechanism disruption, and anterior knee pain. Third, it is a fallacy to think that anterior knee pain (AKP) does not exist despite primary patellar resurfacing in TKA. Meftah (Ranawat) et al found that AKP persists in 30% of patients and new AKP develops in 10% of patients after TKA with patellar resurfacing. Barrack et al found that with patellar resurfacing the incidence of AKP is 28% in patients without preop AKP and 9% in those with preop AKP. They also found that without patellar resurfacing the incidence of new AKP was 14% and persistent AKP was 23%. Fourth, only roughly 44–64% of patients who undergo secondary patellar resurfacing for AKP after TKA with an unresurfaced patella actually get relief of their pain, suggesting that there is some other etiology of anterior knee pain. Residual component malalignment, boxy femoral components, PF overstuffing, referred pain or asymmetric resurfacing may explain ongoing pain. Finally, the data in well-designed studies show that selective patellar resurfacing can produce similar outcomes with and without resurfacing, particularly in those without significant patellar arthritis. In multiple studies, higher rates of secondary surgery occur when the patella is left unresurfaced in primary TKA, but this is for “pain” without clear etiology. On the other hand secondary surgery is rarely performed in TKA with patellar resurfacing for “pain” only, despite its high incidence. The quality of patellar cartilage at the time of primary TKA should be considered, as that may be the best indicator of whether a knee will do well without patellar resurfacing (that is, selective patellar resurfacing may be a better idea than never resurfacing the patella). While patellar resurfacing remains controversial in modern TKA, excellent outcomes are achievable with, and without, primary patellar resurfacing. Selectively leaving the patella unresurfaced when there is limited patellar arthritis may not only be highly effective, but it may also limit the incidence of secondary resurfacing that may occur with more substantial patellar arthritis while also minimizing the risk of some of the devastating complications that can occur due to patellar resurfacing in TKA

Whether to resurface the patella during a primary Total Knee Replacement (TKR) performed as a treatment of degenerative osteoarthritis remain a controversial issue. Patellar resurfacing was introduced because early implants were not designed to accommodate the native patella in an anatomic fashion during the range of motion. Complications related to patella resurfacing became a primary concern and have been associated with the variable revision rates often report post TKR. Subsequent modifications in implant design have been made to offer the surgeon option of leaving the patella un-resurfaced. Numerous clinical trials have been done to determine the superiority of each option. Unfortunately, there is little consensus and surgeon preference remains the primary variable. One of the major reasons given to support patella resurfacing is to eliminate Anterior Knee Pain post operatively. However, studies have shown that this problem was not exclusively found in non-resurfaced patients so the author conclude that anterior knee pain is probably related to component design or to the details of the surgical technique, such as component rotation rather that whether or not the patella is resurfaced. An increasing rate of complications with the extensor mechanism after patellar resurfacing led to the concept of selective resurfacing of the patella in TKR. Decision making algorithms with basis of clinical, radiographic and intraoperative parameters have been developed to determine which patients are suitable for patella resurfacing and which are suitable for patella non-resurfacing. Finally, the continued study of this topic with longer follow up term in randomized, controlled, clinical trials remains essential in our understanding of patella in TKR. The development of joint registry will allow surgeons to draw conclusions on the basis of larger numbers of patients and will improve the reporting of the results of patellar non resurfacing in clinical trials. In general, surgeons in United States always resurface while their counterparts in Europe tend to never resurface

When dealing with the patella in total knee arthroplasty (TKA) there are three philosophies. Some advocate resurfacing in all cases, others do not resurface, and a third group selectively resurfaces the patella. The literature does not offer one clear and consistent message on the topic. Treatment of the patella and the ultimate result is multifactorial. Factors include the patient, surgical technique, and implant design. With respect to the patient, inflammatory versus non-inflammatory arthritis, pre-operative presence or absence of anterior knee pain, age, sex, height, weight, and BMI affect results of TKA. Surgical technique steps to enhance the patellofemoral articulation include: 1) Restore the mechanical axis to facilitate patellofemoral tracking. 2) Select the appropriate femoral component size with respect to the AP dimension of the femur. 3) When performing anterior chamfer resection, measure the amount of bone removed in the center of the resection and compare to the prosthesis. Do not overstuff the patellofemoral articulation by taking an inadequate amount of bone. 4) Rotationally align the femur appropriately using a combination of the AP axis, the transepicondylar axis, the posterior condylar axis, and the tibial shaft axis. 5) If faced with whether to medialise or lateralise the femoral component, always lateralise. This will enhance patellofemoral tracking. 6) When resurfacing the patella, only evert the patella after all other bony resections have been performed. Remove peripheral osteophytes and measure the thickness of the patella prior to resection. Make every effort to leave at least 15 mm of bone and never leave less than 13 mm. 7) Resect the patella. The presenter prefers a freehand technique using the insertions of the patellar tendon and quadriceps tendon as a guide, sawing from inferior to superior, then from medial to lateral to ensure a smooth, flat, symmetrical resection. Medialise the patellar component and measure the thickness of reconstruction. 8) When not resurfacing the patella, surgeons generally remove all the peripheral osteophytes, and some perform denervation using electrocautery around the perimeter. 9) Determine appropriate patellofemoral tracking only after the tourniquet is released. 10) Close the knee in flexion so as not to tether the soft tissues about the patella and the extensor. With or without patellar resurfacing, implant design plays in important role in minimizing patellofemoral complications. Newer designs feature a so-called “swept back” femur in which the chamfer resection is deepened, and patellofemoral overstuffing is minimised. Lateralizing the trochlear groove on the anterior flange, orienting it in valgus alignment, and gradually transitioning to midline have improved patellofemoral tracking. Extending the trochlear groove as far as possible into the tibiofemoral articulation has decreased patellofemoral crepitation and patellar clunk in posterior stabilised designs. With respect to the tibial component, providing patellar relief anteriorly in the tibial polyethylene has facilitated range of motion and reduced patellar impingement in deep flexion. On the patella side, the all-polyethylene patella remains the gold standard. While data exist to support all three viewpoints in the treatment of the patella in TKA, it is the presenter's opinion that the overwhelming data support patella resurfacing at the time of primary TKA. It is clear from the literature that the status of the patellofemoral articulation following TKA is multifactorial. Surgical technique and implant design are key to a well-functioning patellofemoral articulation. Pain is the primary reason patients seek to undergo TKA. Since our primary goal is to relieve pain, and there has been a higher incidence of anterior knee pain reported without patellar resurfacing, why not resurface the patella?