Aims

Revision total knee arthroplasty (rTKA) and revision total hip arthroplasty (rTHA) are complex procedures with higher rates of re-revision, complications, and mortality compared to primary TKA and THA. We report the effects of the establishment of a revision arthroplasty network (the East Midlands Specialist Orthopaedic Network; EMSON) on outcomes of rTKA and rTHA.

Aims. Despite the increase in the surgical repair of proximal hamstring tears, there exists a lack of consensus in the optimal timing for surgery. There is also disagreement on how partial tears managed surgically compare with complete tears repaired surgically. This study aims to compare the mid-term functional outcomes in, and operating time required for, complete and partial proximal hamstring avulsions, that are repaired both acutely and chronically. Methods. This is a prospective series of 156 proximal hamstring surgical repairs, with a mean age of 48.9 years (21.5 to 78). Functional outcomes were assessed preinjury, preoperatively, and postoperatively (six months and minimum three years) using the Sydney Hamstring Origin Rupture Evaluation (SHORE) score. Operating time was recorded for every patient. Results. Overall, significant improvements in SHORE scores were seen at both six months and mid-term follow-up. Preoperatively, acute patients (median score 27.1 (interquartile range (IQR) 22.9)) reported significantly poorer SHORE scores than chronic patients (median score 42.9 (IQR 22.1); p < 0.001). However, this difference was not maintained postoperatively. For partial tears, acutely repaired patients reported significantly lower preoperative SHORE scores compared to chronically reapired partial tears (median score 24.3 (IQR 15.7) vs median score 40.0 (IQR 25.0); p < 0.001) but also significantly higher SHORE scores at six-month follow-up compared to chronically repaired partial tears (median score 92.9 (IQR 10.7) vs. median score 82.9 (IQR 14.3); p < 0.001). For complete tears, there was only a difference in preoperative SHORE scores between acute and chronic groups. Overall, acute repairs had a significantly shorter operating time (mean 64.67 minutes (standard deviation (SD) 12.99)) compared to chronic repairs (mean 74.71 minutes (SD = 12.0); t = 5.12, p < 0.001). Conclusion. Surgical repair of proximal hamstring avulsions successfully improves patient reported functional outcomes in the majority of patients, irrespective of the timing of their surgery or injury classification. However, reducing the time from injury to surgery is associated with greater improvement in patient outcomes and an increased likelihood of returning to preinjury functional status. Acute repair appears to be a technically less complex procedure, as indicated by reduced operating times, postoperative neurological symptoms and number of patients requiring bracing. Acute repair is therefore a preference among many surgeons. Cite this article: Bone Joint J 2020;102-B(10):1419–1427

Aims. To validate the Sydney Hamstring Origin Rupture Evaluation (SHORE), a hamstring-specific clinical assessment tool to evaluate patient outcomes following surgical treatment. Methods. A prospective study of 70 unilateral hamstring surgical repairs, with a mean age of 47.3 years (15 to 73). Patients completed the SHORE preoperatively and at six months post-surgery, and then completed both the SHORE and Perth Hamstring Assessment Tool (PHAT) at three years post-surgery. The SHORE questionnaire was validated through the evaluation of its psychometric properties, including; internal consistency, reproducibility, reliability, sensitivity to change, and ceiling effect. Construct validity was assessed using Pearson’s correlation analysis to examine the strength of association between the SHORE and the PHAT. Results. The SHORE demonstrated an excellent completion rate (100%), high internal consistency (Cronbach’s alpha 0.78), and good reproducibility (intraclass correlation coefficient (ICC) 0.82). The SHORE had a high correlation with the validated PHAT score. It was more sensitive in detecting clinical change compared to the PHAT. A ceiling effect was not present in the SHORE at six months; however, a ceiling effect was identified in both scores at three years post-surgery. Conclusion. This study has validated the SHORE patient reported outcome measure (PROM) as a short, practical, reliable, valid, and responsive tool that can be used to assess symptom and function following hamstring injury and surgical repair. Cite this article: Bone Joint J 2020;102-B(3):388–393

Introduction. Despite generally excellent patient outcomes for Total Knee Arthroplasty (TKA), there remains a contingent of patients, up to 20%, who are not satisfied with the outcome of their procedure. (Beswick, 2012) There has been a large amount of research into identifying the factors driving these poor patient outcomes, with increasing recognition of the role of non-surgical factors in predicting achieved outcomes. However, most of this research has been based on single database or registry sources and so has inherited the limitations of its source data. The aim of this work is to develop a predictive model that uses expert knowledge modelling in conjunction with data sources to build a predictive model of TKR patient outcomes. Method. The preliminary Bayesian Belief Network (BBN) developed and presented here uses data from the Osteoarthritis Initiative, a National Institute of Health funded observational study targeting improved diagnosis and monitoring of osteoarthritis. From this data set, a pared down subset of patient outcome relevant preoperative questionnaire sets has been extracted. The BBN structure provides a flexible platform that handles missing data and varying data collection preferences between surgeons, in addition to temporally updating its predictions as the patient progresses through pre and postoperative milestones in their recovery. In addition, data collected using wearable activity monitoring devices has been integrated. An expert knowledge modelling process relying on the experience of the practicing surgical authors has been used to handle missing cross-correlation observations between the two sources of data. Results. The model presented here has been internally cross validated and has some interesting facets, including the strongest single predictive question of bad outcome for the patient being the presence of lower back pain. Clinical implementation and long term predictive accuracy result collection is ongoing. Discussion. Unsatisfied patients represent a significant minority of TKR recipients, with multiple, multifaceted causal factors both in surgery and out implicated. Historically, focus has been on the role of management and improvement of the surgical factors, which is linked to the fact that surgical factors can often lead to far more disastrous consequences for the patient and the basic principle that “you only improve what you measure.” Growing collection of Patient Reported Outcome Measures by registries around the world has exposed the fact that management of patient factors has lagged behind. (Judge, 2012) Increasingly, the pivotal role of unmet expectations in determining patient satisfaction (Noble, 2006) and the “expectation gap” (Ghomrawi, 2012) between surgeons and patients has been exposed as an opportunity to improve patient outcomes. By developing a model that uses existing surgical expert knowledge to integrate research identified preoperative factors that can be accurately and practically gathered in a clinical setting, a workflow that manages patient expectations in order to optimize outcomes could reduce dissatisfaction rates in TKR recipients. Future work should focus on improving clinical integration and, in the absence of sufficiently wide, deep and complete patient response and predictor datasets, ways of harnessing existing expert knowledge into an evolving predictive tool of patient outcomes

After anterior cruciate ligament (ACL) rupture, reconstructive surgery with a hamstring tendon autograft is often performed. Despite overall good results, ACL re-rupture occurs in up to 10% of the patient population, increasing to 30% of the cases for patients aged under 20 years. This can be related to tissue remodelling in the first months to years after surgery, which compromises the graft's mechanical strength. Resident graft fibroblasts secrete matrix metalloproteinases (MMPs), which break down the collagen I extracellular matrix. After necrosis of these fibroblasts, myofibroblasts repopulate the graft, and deposit more collagen III rather than collagen I. Eventually, the cellular and matrix properties converge towards those of the native ACL, but full restoration of the ACL properties is not achieved. It is unknown how inter-patient differences in tissue remodelling capacity contribute to ACL graft rupture risk. This research measured patient-specific tissue remodelling-related properties of human hamstring tendon-derived cells in an in vitro micro-tissue platform, in order to identify potential biological predictors for graft rupture. Human hamstring tendon-derived cells were obtained from remnant autograft tissue after ACL reconstructions. These cells were seeded in collagen I gels on a micro-tissue platform to assess inter-patient cellular differences in tissue remodelling capacity. Remodelling was induced by removing the outermost micro-posts, and micro-tissue compaction over time was assessed using transmitted light microscopy. Protein expression of tendon marker tenomodulin and myofibroblast marker α-smooth muscle actin (αSMA) were measured using Western blot. Expression and activity of remodelling marker MMP2 were determined using gelatin zymography. Cells were obtained from 12 patients (aged 12–51 years). Patient-specific variations in micro-tissue compaction speed or magnitude were observed. Up to 50-fold differences in αSMA expression were found between patients, although these did not correlate with faster or stronger compaction. Surprisingly, tenomodulin was only detected in samples obtained from two patients. Total MMP2 expression varied between patients, but no large differences in active fractions were found. No correlation of patient age with any of the remodelling-related factors was detected. Remodelling-related biological differences between patient tendon-derived cells could be assessed with the presented micro-tissue platform, and did not correlate with age. This demonstrates the need to compare this biological variation in vitro - especially cells with extreme properties - to clinical outcome. Sample size is currently increased, and patient outcome will be determined. Combined with results obtained from the in vitro platform, this could lead to a predictive tool to identify patients at risk for graft rupture

Aims

To investigate the impact of the Charlson and Elixhauser comorbidity indices on patient-reported outcomes measures (PROMs) following shoulder arthroplasty.

Abstract

Introduction. Variation in resection thickness of the femur in Total Knee Arthroplasty (TKA) impacts the flexion and extension tightness of the knee. Less well investigated is how variation in patient anatomy drives flexion or extension tightness pre- and post- operatively. Extension and flexion stability of the post TKA knee is a function of the tension in the ligaments which is proportional to the strain. This study sought to investigate how femoral ligament offset relates to post-operative navigation kinematics and how outcomes are affected by component position in relation to ligament attachment sites. Method. A database of TKA patients operated on by two surgeons from 1-Jan-2014 who had a pre-operative CT scan were assessed. Bone density of the CT scan was used to determine the medial and lateral collateral attachments. Navigation (OmniNav, Raynham, MA) was used in all surgeries, laxity data from the navigation unit was paired to the CT scan. 12-month postoperative Knee Osteoarthritis and Outcome Score (KOOS) score and a postoperative CT scan were taken. Preoperative segmented bones and implants were registered to the postoperative scan to determine change in anatomy. Epicondylar offsets from the distal and posterior condyles (of the native knee and implanted components), resections, maximal flexion and extension of the knee and coronal plane laxity were assessed. Relationships between these measurements were determined. Surgical technique was a mix of mechanical gap balancing and kinematically aligned knees using Omni (Raynham, MA) Apex implants. Results. 119 patients were identified in the database. 60% (71) were female and the average age was 69.0 years (+/− 8.1). The average distal femoral bone resection was 7.5 mm (+/− 1.6) medially and 5.4 mm (+/− 2.1) laterally, and posterior 10.2 mm (+/− 1.7) medially and 8.4 mm (+/− 1.8) laterally, with implant replacement thicknesses 9 mm distally and 11 mm posterior. Maximum flexion of the knee post implantation was 121.5° (+/− 8.1) from a preoperative value of 117.9° (+/− 9.5). Change in the collateral ligament offsets brought on by surgery had significant correlations with several laxity and flexion measures. Increase in the posterior offset of the medial collateral attachment brought on by surgery was shown to decrease the maximum flexion attained (coefficient = −0.53, p < 0.001), Figure 1. Increased distal medial offset post-operatively compared to the posterior offset is significantly correlated with improved KOOS pain outcomes (coefficient = 0.23, p = 0.01). Similarly, a decrease in the distal offset of the lateral collateral ligament increased the coronal plane laxity in extension (coefficient = 0.37, p < 0.001), while the posterior lateral resection was observed to correlate with postoperative coronal laxity in flexion (coefficient = 0.42, p < 0.001). Conclusions. Accounting for variation in ligament offset during surgically planning may improve balancing outcomes. Although new alignment approaches, such as kinematic alignment, have been able to demonstrate improvements in short term outcomes, elimination of postoperative dissatisfaction has not been achieved. The interaction of an alignment strategy with a given patient's specific anatomy may be the key to unlocking further TKA patient outcome gains

Aims

The timing of surgical fixation in spinal fractures is a contentious topic. Existing literature suggests that early stabilization leads to reduced morbidity, improved neurological outcomes, and shorter hospital stay. However, the quality of evidence is low and equivocal with regard to the safety of early fixation in the severely injured patient. This paper compares complication profiles between spinal fractures treated with early fixation and those treated with late fixation.

Aims

As the population ages, there is projected to be an increase in the level of demand for total knee arthroplasty (TKA) in octogenarians. We aimed to explore whether those aged ≥ 80 years achieved similar improvements in physical function to younger patients while also comparing the rates of length of stay (LOS), discharge to rehabilitation, postoperative complications, and mortality following TKA in older and younger patients.

Acute distal biceps tendon repair reduces fatigue-related pain and minimises loss of forearm supination and elbow flexion strength. We report the short- and long-term outcome following repair using an EndoButton technique. Between 2010 – 2018, 102 patients (101 males; mean age 43 years) underwent acute (□6 weeks) distal biceps tendon repair using an EndoButton technique. The primary short-term outcome was complications. The primary long-term outcome was the Quick-DASH (Q-DASH). Secondary outcomes included the Oxford Elbow Score (OES), EuroQol-5D-3L (EQ-5D), return to function and satisfaction. At mean short-term follow-up of 4 months (2.0 – 55.5) eight patients (7.8%) experienced a major complication and 34 patients (33.3%) experienced a minor complication. Major complications included re-rupture (n=3, 2.9%), unrecovered nerve injury (n=4, 3.9%) and surgery for heterotopic ossification excision (n=1, 1.0%). Three patients (2.9%) required surgery for a complication. Minor complications included neuropraxia (n=27, 26.5%) and superficial infection (n=7, 6.9%). At mean follow-up of 5 years (1 – 9.8) outcomes were collected from 86 patients (84.3%). The median Q-DASH, OES, EQ-5D and satisfaction scores were 1.2 (IQR 0 – 5.1), 48 (IQR, 46 – 48), 0.80 (IQR, 0.72 – 1.0) and 100/100 (IQR, 90 – 100) respectively. Most patients returned to sport (82.3%) and employment (97.6%) following surgery. Unrecovered nerve injury was associated with a poor outcome according to the Q-DASH (p< 0.001), although re-rupture and further surgery were not (p > 0.05). Acute distal biceps tendon repair using an EndoButton technique results in excellent patient reported outcomes and health-related quality of life. Although rare, unrecovered nerve injury adversely affects outcome

Introduction

The purpose of this study was to demonstrate the feasibility of passively collecting objective data from a commercially available smartphone-based care management platform (sbCMP) and robotic assisted total knee arthroplasty (raTKA).

Even though primary total knee arthroplasty involves resurfacing the joint with metal and plastic it is much more of a soft tissue operation than it is a bony procedure. The idea that altering the planned bony resection by a few degrees on either the tibial or femoral side of the joint might somehow eliminate the multifactorial pain complaints and reduced patient satisfaction seen in some 20% or more of cases in reported clinical series is clearly overly optimistic. Axial alignment is important, but no more so than the level of distal femoral resection, tibial and femoral rotation, tibial resection level and downslope and femoral sagittal plane alignment. The real problem is that errors in component positioning are common, rarely made one at a time, and are made more common by greater procedural complexity. No matter the resection method (let alone the resection target!) errors are commonly linked and iterative. For example: femoral malrotation on an under-resected distal femur (in a knee with minimal arthritic wear to begin with) can contribute to corresponding tibial malrotation helped by a “floated” tibial trial on an all too often overly resected and downsloped tibial surface that has been recut to allow full extension with the under-resected femur (and now also results in AP laxity in flexion). Small changes in the alignment target will not fix this!

On the other hand: Kinematic alignment individualised to the patient's anatomy as a means of reducing soft tissue imbalance and minimizing ligamentous releases is actually a reasonable objective and a laudable goal on the surface. The problem with operationalizing this widely relates to what is currently required to try and reliably achieve this goal using currently available implants and technology. In the early 1980's the proponents of “anatomic” alignment with a residual 2- to 3-degree varus tibial resection and corresponding joint obliquity were Hungerford and Krackow. This concept was widely adopted but proved to be fraught with difficulty in the hands of community based surgeons in that era due to common excessive varus tibial resection errors and resulting premature implant failures. Recent reports on kinematic alignment involve a plethora of technology combinations including pre-operative CT (or MRI) for 3D reconstruction and planning, custom jig fabrication, and navigated bony preparation or individualised bony cuts off of patient specific jigs. The goal is to allow customised resections that “estimate” original cartilage thickness and bone erosion and seek to replicate the original however native anatomy and provide better precision for bone resection. Even when successful this is often followed by placement of a standard implant not too different from those in the 80's and 90's which may well have one femoral articular “J curve” for all patents, a single patellofemoral groove design and anatomic shape for all, and that makes use of a central keel on a nonanatomic tibial design with limited sizing increments, all implanted into a patient without an ACL and not infrequently PCL deficient as well. And all of this is done with the hope of restoring the normal original knee kinematics!

The frequent combination of several of the above factors clinically in a single knee may help explain some of the variability in results of kinematic alignment reported by some authors even after excluding certain pre-operative deformities (excess valgus or varus).

For now mechanical alignment methods and instrumentation should remain the standard of care for routine TKA practice for most, and in complex primary cases for all.

Conventional total knee arthroplasty aims to place the joint line perpendicular to the mechanical axis resulting in an overall neutral mechanical alignment. This objective is promulgated despite the fact healthy adult populations are on average in varus with few proximal tibias being neutral to the mechanical axis. The goal of a neutral mechanical axis is based largely on historical studies and the fact that it is easier to make a neutral tibial cut with conventional jigs and the eye. In order to balance the flexion and extension gaps to accommodate a neutral tibial cut, in most patients, asymmetrical distal and posterior femoral cuts are required. The resulting position of the femoral component could be considered to be “mal-rotated” with respect to the patient's soft tissue envelope. Soft tissue releases are often required to “balance” the knee. Planning and execution of the surgery are largely based off 2-dimensional radiographs which grossly oversimplifies the concept of alignment to the coronal plane, largely ignoring what happens to the knee in 3-dimensions through range of motion and 4-dimensions with respect to gait, stair climbing, etc. Subsequently, neutral mechanical for all engenders the “looks good, feels bad” phenomenon seen in many patients that may in part drive the higher dissatisfaction rates seen in knee arthroplasty globally compared to hip arthroplasty.

Additionally, because most tibias are in varus in the native state, placement of the tibial component in a neutral position results in a valgus orientated position during weight bearing post-operatively. Placing the tibial component in a varus, kinematic aligned position negates this deleterious condition and has been linked to improved outcomes in recent studies.

New imaging and surgical techniques allow for the identification of patient specific alignment targets and the ability to more precisely execute the surgical plan with respect to 3-dimensional placement of the components. Long-term outcomes studies as well as more recent studies on “kinematic” positioning suggest that deviation away from a neutral mechanical target is safe with respect to survivorship and provides better function with a more “natural” feeling knee.

Aims

There are comparatively few randomized studies evaluating knee arthroplasty prostheses, and fewer still that report longer-term functional outcomes. The aim of this study was to evaluate mid-term outcomes of an existing implant trial cohort to document changing patient function over time following total knee arthroplasty using longitudinal analytical techniques and to determine whether implant design chosen at time of surgery influenced these outcomes.

Introduction. Varus alignment of the femoral component in total hip arthroplasty (THA) is thought to be a risk factor for implant loosening and early revision surgery. The purpose of this study was to evaluate whether the Exeter stem tolerates varus alignment and assess if this theoretical malalignment has an influence on clinical outcomes. Methods. A total of 4126 consecutive THAs were reviewed for patients between 2006 and 2012 to allow for a minimum five-year follow-up. To determine the effects of the stem alignment on results, the hips were classified into 3 groups on the basis of stem alignment in initial postoperative anteroposterior radiographs. The alignment of the stem was defined as neutral, valgus (≥ 3° of lateral deviation), or varus (≥ 3° of medial deviation). The primary outcome was all cause revision with patient related outcomes assessed with Oxford hip score pre and post-operatively. Results. The mean follow-up period was 8.6 years. 3803 (92.2%), 48 (1.2%), and 275 (6.7%) hips were assessed as neutral, valgus, and varus alignment, respectively. Assessment of outcomes showed that 75 revision surgeries (1.8%) were performed during follow-up for a variety of causes but there was no significant difference in the revision rate among the 3 alignment groups. No stems were revised for aseptic loosening in any of the three groups. Oxford Hip scores were obtained at a mean of 4.6 years post-operatively and no significant difference in patient reported outcome was identified between the different alignment groups. Conclusion. This study suggests that the Exeter stem tolerates varus alignment well with no demonstrable effect on revision rate or patient reported outcome. This tolerance of malposition compared to the negative results reported in the literature with other stem designs can be of reassurance to surgeons using the Exeter system

Background Joint replacement remains the most effective healthcare measure in improving patient health related quality of life (HRQOL) and pain incompatible with normal daily living remains the primary indication for both hip and knee arthroplasty. Quality of life outcome and patient satisfaction after total hip arthroplasty are complex phenomena and many confounding determinants have been identified. Degenerative disease of the hip joint may present with variable patterns of pain referral in the lower limb. However the effect of varied pain referral patterns on patient outcome and satisfaction after total hip arthroplasty has not previously been examined. Methods From 2000 to 2003, 236 eligible patients scheduled to undergo primary total hip arthroplasty were prospectively enrolled. The principle pain referral pattern (as hip, thigh or knee) was identified in all patients. HRQOL was examined using the Harris Hip score (HHS), the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and the 36-Item Short-Form Health Survey (SF-36) pre-operatively, 1 year and 2 years postoperatively and with the HHS at 3 months postoperatively. All patients were followed up for a minimum of 2 years. Results The frequency of the pain referral distributions were; hip pain 41%, knee pain 32% and thigh pain 27%. Patients in all groups were comparable preoperatively with respect to age; HHS, and both mean and domain specific WOMAC and SF-36 scores. The mean duration of symptoms was significantly greater in patients with knee pain when compared to the remaining two pain patterns. All patients demonstrated as expected improvements in HHS, SF-36 and WOMAC scores after surgery. At all times postoperatively there were significant differences in mean HHS and mean and domain specific WOMAC and SF-36 scores between patients with hip or thigh pain and those with knee pain (p< 0.001). While notable, differences between hip and thigh pain were not as consistent however. Conclusions Pre-operative pain referral patterns of hip arthritis determine patient outcome and satisfaction after total hip arthroplasty, as measured using validated HRQOL scoring systems. Level of evidence Level I-1 (Prognostic Study-Investigating the Outcome of Disease. Prospective study)

Aims

Total wrist arthrodesis (TWA) produces a spectrum of outcomes. We investigated this by reviewing 77 consecutive TWA performed for inflammatory and post-traumatic arthropathies, wrist instability and as a salvage procedure.

Bone transport/limb lengthening with circular external fixation has been associated with a prolonged period of time in the frame and a significant major complication rate following frame removal. We examined the results of bone transport in fifty-one limbs using the “monorail” technique and found a dramatically improved lengthening index (24.5 days/cm. – time in frame /cm. of length gained) and an absence of refracture or angulatory deformity following fixator removal. This technique is our treatment of choice for limb lengthening/bone transport. We sought to determine patient oriented outcome and complication rates following b one transport using an external fixator placed over an intramedullary nail (the “monorail” technique). Bone transport using the monorail technique is associated with a dramatically improved lengthening index and a lower major complication rate than traditional ring fixator methods. Patient satisfaction with the procedure was high. Our study confirms the significant advantages of the monorail technique for bone transport/limb lengthening. The time in the fixator is dramatically reduced, and complications associated with earlier techniques such as angulatory deformity or refracture were not seen. We identified forty-nine patients (fifty-one limbs) who had undergone bone transport using the monorail technique (external fixator placed over an intramedullary nail). There were thirty-five men and fourteen women with a mean age of thirty-five years (range 17–50). Pre-operative diagnoses included post traumatic length discrepancy/bone defect (forty-one), congenital short stature (six) and other (four). All patients had a unilateral fixator placed over an implanted intramedullary nail. Once length correction was achieved, the fixator was removed and the nail “locked”. The mean amount of lengthening was 5.5 cm. (range 2 – 18 cm.). The lengthening index was 24.5 days /cm. (duration of external fixation/cm. bone length gained), with a range from ten to fifty days /cm. There were nineteen complications (thirty-seven percent): nine premature consolidations, four infected pin sites, two hardware failures, two osteomyelitis, one DVT, one nonunion. There were no refractures, angulatory deformities or cases of intramedullary sepsis

The effect of pre-operative pain, physical function, mental function and multiple patient factors on patient outcome following TKR was examined. After informed consent, 105 patients undergoing primary TKR completed preoperative SF-36 and WOMAC questionnaires and a Knee Society Score (KSS) was determined. These scores were repeated at 12 months. Patient data studied included age, gender, BMI and significant comorbid conditions such as diabetes, cardiac disease, and COPD. Statistical analysis included a univariate analysis, followed by a bivariate analysis and multiple regression analysis. All physical dimensions of the SF-36, WOMAC and KSS showed highly significant improvements after one year. The KSS improved to a mean of 94.8 (p< 0.000001). For patients greater than 65 years of age, postoperative physical function was returned to normative scores for age matched controls. For patients less than 65, physical function did not reach age matched controls even though similar improvements in physical function were seen. Patients with lower physical function scores (PCS) pre-operatively showed greater improvement postoperatively yet did not reach the same absolute level of function as patients who had higher preoperative physical function. The mean PCS for men increased from 35 to 42, while for women it increased from 29 to 42 (p=0.042). Preoperative mental function (MCS) was a strong predictor of postoperative physical function. Patients with low preoperative MCS and one or more comorbid conditions were 10.1 times more likely to have a poor outcome following TKR. Knowledge of preoperative physical function, mental function, gender, age and comorbid conditions improves prediction of post-operative physical function after TKR. Patients at high risk for little improvement following TKR are those with low preoperative mental function (MCS< 50) in addition to one or more comorbid conditions. These patients can be identified during the pre-operative period