Since the publication by Berger in 1993, many total knee replacements (TKR) have been measured using his technique to assess component rotation. Whereas the femoral landmarks have been showed to be accurate and precise, the use of the tibial tuberosity to ascertain the true tibial orientation is more controversial. The goal of this study was to identify a new anatomical landmark to measure tibial component rotation.

211 CTs performed after TKR were reviewed. The authors noticed that the lateral cortex of the tibia below the tibial plateau component was flat over a depth of approximately 10mm. A protocol to measure tibial rotation in relation to this landmark was developed: the slice below the tibial plateau was identified; a primary line was drawn over the straight lateral cortex of the tibia; a perpendicular to this line defined the reference axis (A); the posterior tibial component axis was drawn (B); the angle between A and B was measured with internal rotation being negative and external positive. Two independent observers measured 31 CTs twice each and Intraclass Correlation Coefficients (ICC) were calculated for intra- and inter-observer error. The 211CTs were measured according to Berger's and this protocol.

Intra-observer ICCs were 0.812 for Observer1 and 0.806 for Observer2. The inter-observer ICCs were 0.699 for Reading1 and 0.752 for Reading2. The Berger protocol mean tibial rotation was 9.7°±5.5° (−29.0° to 5.2°) and for the new landmark 0°±5.4° (−18.6° to 14°).

This new tibial landmark appeared easy to identify and intra- and inter-observer errors were acceptable. The fact that the mean tibial rotation was 0° makes this landmark attractive. A consistent easily identified landmark for tibial rotation may allow for improvement in component rotation and the diagnosis of dissatisfaction after TKR. Further studies are under way to confirm the relevance of this landmark.

In recent years there has been growing interest in enhanced recovery regimes in lower limb arthroplasty due to potential clinical benefits of early mobilisation along with cost-savings. Following adoption of this regime in a district general hospital, it was observed that traditional dressings were a potential barrier to its success with ongoing wound problems in patients otherwise fit for discharge. The aim of this audit was to assess current wound care practice, implement a potentially improved regime and re-evaluate practice.

A prospective clinical audit was performed over a three month period involving 100 patients undergoing hip or knee arthroplasty. Fifty patients with traditional dressings were evaluated prior to change in practice to a modern dressing (Aquacel™ Surgical). Fifty patients were then evaluated with the new dressing to complete the audit cycle. Clinical outcome measures included wear time, number of changes, blister rate and length of stay. Statistical comparisons were performed using Mann Whitney or Fisher's Exact test (statistical significance, p<0.05).

Wear time for the traditional dressing (2 days) was significantly shorter than the modern dressing (7 days), p<0.001, and required more changes (0 vs. 3 days), p<0.001. 20% of patients developed blisters with the traditional dressing compared with 4% with the modern dressing (p=0.028). Length of stay was the same for the modern dressing (4 days) compared with the traditional dressing (4 days). However, in the modern group 75% of patients were discharged by day 4 whereas in the traditional group this took until day 6.

This audit highlights the problems associated with traditional dressings with frequent early dressing changes, blistering and delayed discharge. These adverse outcomes can be minimised with a modern dressing specifically designed for the demands of lower limb arthroplasty. Units planning to implement enhanced recovery regimes should consider adopting this dressing to avoid compromising patient discharge.

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting.

We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3 mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation.

Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6 mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3 mm).

These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology.

This study aimed to overcome the subjective nature of routine assessment of knee laxity and develop a repeatable, objective method using a hand-held force application device (FAD).

Eighteen clinicians (physiotherapists, consultants, trainees) volunteered to measure the coronal angular deviation of the right knee of a healthy volunteer using a validated non-invasive infrared measuring system. Effort was taken to ensure the knee flexion angle (∼2°) and hand positions were constant during testing. Three varus and valgus stress tests were conducted, in which maximum angular deviation was determined and subsequently averaged, in the following order of conditions: manual stress without the FAD up to a perceived end-point (before); with the FAD to apply a moment of 18 Nm; and again without the FAD (after). A repeated measures ANOVA was used to analyse the results.

All three groups of clinicians produced measurements of valgus laxity with consistent mean values and standard deviations (<1°) for each condition. For varus mean values were consistent but standard deviations were larger.

Valgus deviations varied significantly between conditions (p < 0.01), with deviations achieved using the FAD greater than both before (p < 0.01) and after (p < 0.05) indicating that the perceived endpoints were less than that achieved at 18 Nm. However varus perceived endpoints were no different to that achieved at 18 Nm, suggesting that clinicians usually apply a greater valgus moment than varus. Furthermore, the non-significant increase in valgus deviation between before and after (p = 0.123) is suggestive of a training trend, especially for trainees.

Our standardised knee laxity assessment may have a role in improving the balancing techniques of TKA and the diagnosis of collateral ligament injuries. Also, by quantifying the technique of senior clinicians, and with use of the FAD, the perceptive skills of more junior trainees may be enhanced.

The Columbus is a relatively new implant with no published medium or long term follow-up. Its extensive use within our department led to this study to review the five-year clinical outcomesof patients who had a navigated Columbus primary total knee arthroplasty (TKA) implanted between March 2005 and December 2006.

Case notes, departmental and hospital databases and PACS were used to identify patients and collect routine five-year review data. Information Services Division was approached for all cases of re-admission and associated complications anywhere in Scotland.

219 (90 male, 116 left) patients were identified. Mean age was 69 years (48–89) and mean BMI 32.2 (SD 5.8). Of the 219 patients operated on, twenty-one had a complication; ten still had intermittent mild to moderate pain, three had wound problems, one had a washout, one had DVT/PE within ninety days and one was diagnosed with patellar clunk syndrome. The remaining five patients had revision TKA (revision rate 2.3%), four for infection and only one due to aseptic loosening (revision rate excluding infection 0.5%). 115 patients returned to clinic at five years. Of these 96.4% were satisfied with their operation. The mean Oxford knee score had reduced from 42.5 (SD 8.2) pre-operatively to 23.6 (SD 9.2). Mean fixed flexion was 1° (SD 2.8°, range 0° to 15°) with four patients having a fixed flexion of 6° or more. Mean maximum flexion was 100° (SD 10.2°, range 60° to 120°) with two patients having flexion less than 80°. X-ray analysis showed that fourteen patients had a radiolucent line. Nine of these were not present at one year, six being at the tibial component.

These results are satisfactory. The revision rate is similar to that cited by the National Joint Registry report 2011 (2.5%). Furthermore, the revision rate excluding infection is very low.

This study measured the three bony axes usually used for femoral component rotation in total knee arthroplasty and compared the accuracy and repeatability of different measurement techniques.

Fresh cadaveric limbs (n=6) were used. Three observers (student, trainee and consultant) identified the posterior condylar (PCA), anteroposterior (AP) and the transepicondylar (TEA) axes, using a computer navigation system to record measurements. The AP axis was measured before and after being identified with an ink line. The TEA was measured by palpation of the epicondyles both before and after an incision was made in the medial and lateral gutters at the level of the epicondyles, allowing the index finger to be passed behind the gutters. In addition the true TEA was identified after dissection of all the soft tissues. Each measurement was repeated three times. For all axes and each observer the repeatability coefficient was calculated.

The identification of the PCA was the most reliable (repeatability coefficient: 1.1°) followed by the AP after drawing the ink line (4.5°) then the AP before (5.7°) and lastly the TEA (12.3°) which showed no improvement with the incisions (13.0°). In general the inter-observer variability for each axis was small (average 3.3°, range 0.4° to 6°), being best for the consultant and worst for the student. In comparison to the true TEA, the recorded TEA and AP axis averaged within 1.5° whilst the PCA was consistently 2.8° or more internally rotated.

This study echoed previous studies in demonstrating that palpating the PCA intra-operatively is highly precise but was prone to errors in representing the true TEA if there was asymmetrical condylar erosion. The TEA was highly variable irrespective of observer ability and experience. The line perpendicular line to the AP axis most closely paralleled the true TEA when measured after being identified with an ink line.

Distal femur resection for correction of flexion contractures in total knee arthroplasty (TKA) can lead to joint line elevation, abnormal knee kinematics and patellofemoral problems. The aim of this retrospective study was to establish the contribution of soft tissue releases and bony cuts in the change in maximum knee extension in TKA.

Data were available for 211 TKAs performed by a single surgeon using a medial approach. Intra-operatively pre- and post-implant extension angles and the size of bone resection were collected using a commercial navigation system. The thickness of polyethylene insert and the extent of soft tissue release performed (no release, moderate and extensive release) were collected from the patient record. A linear model was used to predict change in maximum extension from pre- to post-implant.

The analysis showed that bone cuts (p<0.001), soft tissue release (p=0.001) and insert thickness (p=0.010) were all significant terms in the model (r²_adj=0.170). This model predicted that carrying out a TKA with 19 mm bone cuts, 10 mm insert and no soft tissue release would give 4.2° increase in extension. It predicted that a moderate release would give a further 2.8° increase in extension with an extensive release giving 3.9°. For each mm increase in bone cuts the model predicted an 0.8° increase in extension and for each mm increase in insert size a decrease extension by 1.1°.

The modelling results show that in general to increase maximum extension by the same as an extensive soft tissue release that bone cuts would have to be increased by 4–5 mm. However this model only accounted for 17% of the variation in change in extension pre- to post-implant so may not be accurate at predicting outcomes for specific patients.

Patient reported outcome measures (PROMs) are important for assessing the results of lower limb arthroplasty. Unrealistic or uneducated expectations may have a significant negative impact on PROMs even when surgery is technically successful. This study's aim was to quantify pre-operative expectations of Scottish patients undergoing total hip and knee replacement (THR/TKR).

100 THR and 100 TKR patients completed validated questionnaires (from the Hospital for Special Surgery) prior to their operation after receiving standard pre-operative information (booklet, DVD, consultations). Each patient rated expectations from very important to not having the expectation. A total score was calculated using a numerical scale for the grading of each expectation. Univariate regression analysis was used to investigate the relationship between demographics and expectation score.

The THR cohort had mean age 66.2 (SD 10.5), 53% female, mean BMI 29.0 (SD 5.1) and mean Oxford score 44 (SD 7). The TKR cohort had mean age 67.6 (SD 8.5), 59% female, mean BMI 32.8 (SD 5.8) and mean Oxford score 44 (SD 8). 100% THR and 96% TKR patients had 10 or more expectations of their operation. All expected pain relief. Other improvements expected were: walking for 100% THA and 99% TKA patients; daily activities for 100% THAs and 96% TKAs; recreational activities for 96% THAs and 93% TKAs; sexual activity for 66% THAs and 59% TKAs; psychological well-being for 98% THAs and 91% TKAs. Regression analysis showed increasing age lowered expectations in both THR (p=0.025) and TKR (p=0.031) patients but that gender, BMI and Oxford score were not significantly related to expectations.

This study highlights that patients expect far more than pain relief and improved post-operative mobility from their operation. It is important to discuss and manage these expectations with patients prior to surgery. By doing so, patient satisfaction and PROMs should further improve.

Non-invasive assessment of lower limb mechanical alignment and assessment of knee laxity using navigation technology is now possible during knee flexion owing to recent software developments. We report a comparison of this new technology with a validated commercially available invasive navigation system.

We tested cadaveric lower limbs (n=12) with a commercial invasive navigation system against the non-invasive system. Mechanical femorotibial angle (MFTA) was measured with no stress, then with 15 Nm of varus and valgus moment. MFTA was recorded at 10° intervals from full knee extension to 90° flexion. The investigator was blinded to all MFTA measurements. Repeatability coefficient was calculated to reflect each system's level of precision, and agreement between the systems; 3° was chosen as the upper limit of precision and agreement when measuring MFTA in the clinical setting based on current literature.

Precision of the invasive system was superior and acceptable in all conditions of stress throughout flexion (repeatability coefficient <2°). Precision of the non-invasive system was acceptable from extension until 60° flexion (repeatability coefficient <3°), beyond which precision was unacceptable. Agreement between invasive and non-invasive systems was within 1.7° from extension to 50° flexion when measuring MFTA with no varus / valgus applied. When applying varus / valgus stress agreement between the systems was acceptable from full extension to 30° knee flexion (repeatability coefficient <3°). Beyond this the systems did not demonstrate sufficient agreement.

These results indicate that the non-invasive system can provide reliable quantitative data on MFTA and laxity in the range relevant to knee examination.

Local infiltration analgesia is a relatively novel technique developed for effective pain control following total knee replacement, reducing requirements of epidural or parenteral post-operative analgesia. The study aimed to investigate the anatomical spread of Local Infiltration Analgesia (LIA) used intra-operatively in total knee arthroplasty (TKA) and identify the nerve structures reached by the injected fluid.

Six fresh-frozen cadaveric lower limbs were injected with 180ml of a solution of latex and India ink to enable visualisation. Injections were done according to our standardised LIA technique. Wounds were closed and limbs were placed flat in a freezer at −20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations.

Injected solution was found from the proximal thigh to the middle of the lower leg. The main areas of concentration were the popliteal fossa, the anterior aspect of the femur and the subcutaneous tissue of the anterior aspect of the knee. There was less solution in the lower popliteal fossa. The solution was found to reach the majority of the terminal branches of the tibial, fibular and obturator nerves.

Overall, there was good infiltration of nerves supplying the knee. The lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution that travelled distally to the extensor muscles of the lower leg probably has no beneficial analgesic effect for a TKA patient. This LIA technique reached most nerves that innervate the knee joint which supports the positive clinical results from this LIA technique. However, there may be scope to optimise the injection sites.

Recent debate about changing population demographics and growing demands of younger patients has suggested a future explosion in the requirements for primary and revision lower limb arthroplasty (TKA/THA). This could represent a significant challenge for healthcare providers. This study aimed to predict the demands for lower limb arthroplasty in Scotland from 2010–2035.

Population figures (2004–2010) and projected population data (five year increments) were obtained from the National Records of Scotland. The numbers of arthroplasties from 2004–2010 were provided by the Scottish Arthroplasty Project. Data were divided into three age groups (40–69, 60–79, 80+). The first model used mean incidence for each age group from 2006–2010 applied to the projected population figures. The second used linear regression to give predicted incidences 2015–2035 which were then applied to the projected population. The third-for revisions – used incidence per number of primary arthroplasties.

For primary TKA model 1, comparing to 2010, showed demand increasing by 10% in 2020 and by 31% (to 8,650 procedures) in 2035. Model 2 gave increases of 60% and 161% respectively. An increase was found across all age groups with 60–79 more than doubling and 80+ increasing fourfold by 2035 (model 2). The revision TKA models predicted between 670 and 2,000 procedures by 2035. For primary THA models 1 and 2 showed demand increasing by 40% in 2020 and then by 60% and 110% (11,000 and 14,500 procedures) in 2035 respectively. All age groups had increasing demand with 60–79 doubling and 80+ tripling by 2035 (model 2). The revision THA models predicted between 1,300 and 2,100 procedures by 2035.

These projections show large increases in the numbers of both primaries and revisions over the next two decades. They highlight that current resources may be insufficient or the selection criteria for surgery may need to be revisited.

Knee alignment is a fundamental measurement in the assessment, monitoring and surgical management of patients with OA. In spite of extensive research into the consequences of malalignment, there is a lack of data regarding the potential variation between supine and standing (functional) conditions. The purpose of this study was to explore this relationship in asymptomatic, osteoarthritic and prosthetic knees. Our hypothesis was that the change in alignment of these three groups would be different.

Infrared position capture was used to assess knee alignment for 30 asymptomatic controls and 31 patients with OA, before and after TKA. Coronal and sagittal mechanical femorotibial (MFT) angles in extension (negative values varus/hyperextension) were measured supine and in bi-pedal stance and changes analysed using a paired t-test. To quantify this change in 3D, vector plots of ankle centre displacement relative to the knee centre were produced.

Alignment in both planes changed significantly from supine to standing for all three groups, most frequently towards relative varus and extension. In the coronal plane, the mean±SD(°) of the supine/standing MFT angles was 0.1±2.5/−1.1±3.7 for asymptomatic (p=0.001), −2.5±5.7/−3.6±6.0 for osteoarthritic (p=0.009) and −0.7±1.4/ −2.5±2.0 for prosthetic knees (p<0.001). In the sagittal plane, the mean±SD(°) of the supine/standing MFT angles was −1.7±3.3/−5.5±4.9 for asymptomatic (p<0.001), 7.7±7.1/1.8±7.7 for osteoarthritic (p<0.001) and 6.8±5.1/1.4±7.6 for prosthetic knees (p<0.001). The vector plots showed that the trend of relative varus and extension in stance was similar in overall magnitude and direction between the groups.

The similarities between each group did not support our hypothesis. The consistent kinematic pattern for different knee types suggests that soft tissue restraints rather than underlying joint deformity may be more influential in dynamic control of alignment from lying to standing. This potential change should be considered when positioning TKA components on supine limbs as post-operative functional alignment may be different.

Range of motion (ROM) is a well recognised outcome measure following TKA and combines both knee flexion and extension. In contrast to achieved flexion, fewer studies have recognised the importance of fixed flexion deformity (FFD). A post-operative FFD can adversely affect pain and functional knee scores and so its detection is important. The aim of this study was to investigate the accuracy of standard clinical ROM measurement techniques following TKA and determine their reliability for recognising FFD.

Thirty patients six weeks post-TKA had knee ROM measurements performed with an infrared (IR) tracking system of ±1 accuracy. The patients were also assessed independently by experienced arthroplasty practitioners using a standardised goniometric measurement technique. For goniometric clinically-measured flexion (Clin_flex) and extension (Clin_ext) linear models were generated using IR-measured flexion and extension (IR_flex and IR_ext), BMI and gender as covariables. Data for extension was categorised as FFD present or absent based on Ritter's criteria and agreement was assessed using Kappa.

For both models neither BMI nor gender were significant variables. Models were Clin_flex = 0.54 + 0.66∗IR_flex (r²_adj=0.521) and Clin_ext = 0.23 + 0.50∗IR_ext (r²_adj=0.247), showing that for every 10° increase in flexion, clinical measurement only increased by 7° and for every 10° increase in FFD angle, clinical measurement only increased by 5°. In identifying FFD there was moderate agreement between the two measurements (κ=0.44) with disagreement for nine patients all being patients with FFD that were not identified clinically.

For both flexion and extension there was a greater tendency for the goniometric clinical measurements to underestimate the actual angle. In the context of TKA outcome for maximum flexion this may be preferable to overestimating. In contrast, underestimating the degree of flexion when the knee is in the extended position is not desirable as it will potentially underreport the frequency and magnitude of FFD.

Fixed flexion contracture (FFC) following total knee arthroplasty (TKA) is a source of morbidity for patients. This retrospective review of pre- and post-operative data for 811 total knee replacements with two year follow up aimed to identify pre-operative risk factors for developing FFC and quantify the effect of FFC on outcomes. The incidence of FFC two years post-operation was 3.6%. Advanced age was associated with increased rate of FFC (p=0.02) Males were 2.6 times more likely than females to have FFC at two years (p=0.012). Patients with pre-implant FFC were 2.95 times more likely than those without to have FFC (p=0.028). BMI was not a risk factor (p=0.968). Patients with FFC had poorer outcomes (Oxford Knee Score p=0.003, patient satisfaction p=0.036). The results of this study support the existing literature and clarify a previously contentious point by excluding BMI as a risk factor.

Assessment of coronal knee laxity via manual stress testing is commonly performed during joint examination. While it is generally accepted that the knee should be flexed slightly to assess its collateral restraints, the importance of the exact degree of flexion at time of testing has not been documented. The aim of this study therefore was to assess the effect of differing degrees of knee flexion on the magnitude of coronal deflection observed during collateral stress testing.

Using non-invasive infrared technology, the real-time coronal and sagittal mechanical femorotibial (MFT) angles of three asymptomatic volunteers were measured. A single examiner, blinded to the real-time display of coronal but not sagittal alignment, held the knee in maximum extension and performed manual varus and valgus stress manoeuvres to a perceived end-point. This sequence was repeated at 5° increments up to 30° of flexion. This provided unstressed, varus and valgus coronal alignment measurements as well as overall envelope of laxity (valgus angle – varus angle) which were subsequently regressed against knee flexion.

Regression analysis indicated that all regression coefficients were significantly different to zero (p < 0.001). With increasing knee flexion, valgus MFT angles became more valgus and varus MFT angles became more. The overall laxity of the knee in the coronal plane increased approximately fourfold with 30° of knee flexion.

The results demonstrated that small changes in knee flexion could result in significant changes in coronal knee laxity, an observation which has important clinical relevance and applications. For example the assessment of medial collateral ligament (MCL) injuries can be based on the perceived amount of joint opening with no reference made to knee flexion at time of assessment. Therefore, close attention should be paid to the flexion angle of the knee during stress testing in order to achieve a reliable and reproducible assessment.

Patients undergoing total knee arthroplasty (TKA) experience significant post-operative pain. We report the results of a new comprehensive patient care plan to manage peri-operative pain, enable early mobilisation and reduce length of hospital stay in TKA.

A prospective audit of 1081 patients undergoing primary TKA during 2008 and 2009 was completed. All patients followed a planned programme including pre-operative patient education, pre-emptive analgesia, spinal/epidural anaesthesia with propofol sedation, intra-articular soft tissue wound infiltration, post-operative high volume intermittent ropivacaine boluses with an intra-articular catheter and early mobilisation. The primary outcome measure was the day of discharge from hospital. Secondary outcomes were verbal rating pain scores on movement, time to first mobilisation, nausea and vomiting scores, urinary catheterisation for retention, need for rescue analgesia, maximum flexion at discharge and six weeks post-operatively, and Oxford score improvement.

The median day of discharge to home was post-operative day four. Median pain score on mobilisation was three for first post-operative night, day one and day two. 35% of patients ambulated on the day of surgery and 95% of patients within 24 hours. 79% patients experienced no nausea or vomiting. Catheterisation rate was 6.9%. Rescue analgesia was required in 5% of cases. Median maximum flexion was 85° on discharge and 93° at six weeks post-operatively. Only 6.6% of patients had a reduction in maximum flexion (loss of more than 5°) at six weeks. Median Oxford score had improved from 42 pre-operatively to 27 at six weeks post-operatively. The infection rate was 0.7% and the DVT and PTE rates were 0.6% and 0.5% respectively.

This multidisciplinary approach provides satisfactory post-operative analgesia allowing early safe ambulation and discharge from hospital. Anticipated problems did not arise, with early discharge not being detrimental to flexion achieved at six weeks and infection rates not increasing with the use of intra-articular catheters.

The assessment of knee laxity by application of varus and valgus stress is a subjective clinical manoeuvre often used for soft tissue balancing in arthroplasty or for diagnosis of collateral ligament injuries. Quantitative adjuncts such as stress radiographs have enabled a more objective measurement of angular deviation but may be limited by variations in examination technique. The aim of this study was to quantify clinical knee laxity assessment by measurement of applied forces and resultant angulations.

A novel system for measuring the manually-applied forces and moments was developed. Both hardware and software components underwent laboratory validation prior to volunteer testing. Two clinicians performed multiple blinded examinations on two volunteers and the corresponding angular deviations were measured using a validated non-invasive system with a repeatability of ±1° for coronal alignment. The distance between the kinematically-determined knee and ankle centres was used as the moment arm.

Comparison of single measurements of laxity showed a wide intra- and inter-observer variation (up to 3°). However, when the median value of repeated measurements was used there was good repeatability for both a single surgeon on different days and between the two clinicians with angular measurements agreeing within 1°. In spite of this agreement, the magnitudes of the tangential forces and moments applied varied between clinicians and did not correlate with the corresponding angular deviations.

It was not possible to standardise clinical examination using the current system. Orientation of the applied force with respect to the leg was not quantified and during force measurement it became apparent that the assumed tangential direction of application was not true. This may explain the lack of correlation between the force and angulation data. However, for quantitative measurement of coronal knee laxity using non-invasive laxity measurements, the use of a repeated measures protocol may be accurate enough for clinical application.