Clinical signs and anatomical correlation of patellar tendinitis

Background:

Patellar tendinitis is one of the several differential diagnosis of anterior knee pain. The clinical diagnosis of patellar tendinitis is based on tenderness to palpation at the inferior pole of the patella. The tenderness has been noted to be maximal when the knee is extended and the quadriceps relaxed, but a definite clinical sign for diagnosis is lacking. The accuracy of two clinical signs was assesed by a two-stage study which included physical examination, MRI and a cadaveric study.

Materials and Methods:

Two clinical signs, the “passive flexion-extension sign” and the “standing active quadriceps sign” were assessed in 10 consecutive patients with presumed patellar tendinitis. Five patients had an MRI, showed focal abnormality in the tendon. The location of the MRI finding corresponded, to the region of maximal tenderness. A cadaveric dissection was undertaken to describe the anatomy of the patella and the patellar tendon during these tests.

Results:

Both tests showed a significant decrease in tenderness at the area of inflammation when the patellar tendon was under tension. The cadaveric dissection showed that when the knee is flexed to 90° or when the quadriceps is tensioned the deep fibers of the tendon do not deform to anteriorly applied pressure.

Conclusion:

We suggest using these studies routinely in the evaluation of patients with anterior knee pain.     

Differences in patellofemoral kinematics between weight‐bearing and non‐weight‐bearing conditions in patients with patellofemoral pain

Patellar maltracking is thought to be one source of patellofemoral pain. Measurements of patellar tracking are frequently obtained during non‐weight‐bearing knee extension; however, pain typically arises during highly loaded activities, such as squatting, stair climbing, and running. It is unclear whether patellofemoral joint kinematics during lightly loaded tasks replicate patellofemoral joint motion during weight‐bearing activities. The purpose of this study was to: evaluate differences between upright, weight‐bearing and supine, non‐weight‐bearing joint kinematics in patients with patellofemoral pain; and evaluate whether the kinematics in subjects with maltracking respond differently to weight‐bearing than those in nonmaltrackers. We used real‐time magnetic resonance imaging to visualize the patellofemoral joint during dynamic knee extension from 30° to 0° of knee flexion during two conditions: upright, weight‐bearing and supine, non‐weight‐bearing. We compared patellofemoral kinematics measured from the images. The patella translated more laterally during the supine task compared to the weight‐bearing task for knee flexion angles between 0° and 5° (p = 0.001). The kinematics of the maltrackers responded differently to joint loading than those of the non‐maltrackers. In subjects with excessive lateral patellar translation, the patella translated more laterally during upright, weight‐bearing knee extension for knee flexion angles between 25° and 30° (p = 0.001). However, in subjects with normal patellar translation, the patella translated more laterally during supine, non‐weight‐bearing knee extension near full extension (p = 0.001). These results suggest that patellofemoral kinematics measured during supine, unloaded tasks do not accurately represent the joint motion during weight‐bearing activities. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:312–317, 2011     

Three‐dimensional patellar motion at the natural knee during passive flexion/extension. An in vitro study

Patellar maltracking may result in many patellofemoral joint (PFJ) disorders in the natural and replaced knee. The literature providing quantitative reference for normal PFJ kinematics according to which patellar maltracking could be identified is still limited. The aim of this study was to measure in vitro accurately all six‐degrees‐of‐freedom of patellar motion with respect to the femur and tibia on 20 normal specimens. A state‐of‐the‐art knee navigation system, suitably adapted for this study aim, was used. Anatomical reference frames were defined for the femur, tibia, and patella according to international recommendations. PFJ flexion, tilt, rotation, and translations were calculated in addition to standard tibiofemoral joint (TFJ) kinematics. All motion patterns were found to be generally repeatable intra‐/interspecimens. PFJ flexion was 62% of the corresponding TFJ flexion range; tilt and translations along femoral mediolateral and tibial proximodistal axes during TFJ flexion were found with medial, lateral, and distal trends and within 12°, 6 and 9 mm, respectively. No clear pattern for PFJ rotation was observed. These results concur with comparable reports from the literature and contribute to the controversial knowledge on normal PFJ kinematics. Their consistence provides fundamental information to understand orthopedic treatment of the knee and for possible relevant measurements intraoperatively. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1426–1431, 2009     

In vivo comparison of medialized dome and anatomic patellofemoral geometries using subject‐specific computational modeling

Successful outcome following total knee arthroplasty (TKA) with patella resurfacing is partly determined by the restoration of patellofemoral (PF) function and recovery of the quadriceps mechanism. The current study compared two patellar TKA geometries (medialized dome and anatomic) to determine their impact on PF mechanics and quadriceps function. In‐vivo, subject‐specific patellar mechanics were evaluated using a sequential experimental and modeling approach. First, stereo radiography, marker‐based motion capture, and force plate data were collected for TKA patients (10 dome, 10 anatomic) performing a knee extension and lunge. Second, subject‐specific, whole‐body, musculoskeletal models, including 6 degrees‐of‐freedom (DOF) knee joint kinematics, were created for each subject and activity to predict quadriceps forces. Last, finite element models of each subject and activity were created to predict PF kinematics, patellar loading, moment arm, and patellar tendon angle. Differences in mechanics between dome and anatomic patients were highlighted during load‐bearing (lunge) activity. Anatomic subjects demonstrated greater PF flexion angles (avg. 11 ± 3°) compared to dome subjects during lunge. Similar to the natural knee, contact locations on the patella migrated inferior to superior as the knee flexed in anatomic subjects, but remained relatively superior in dome subjects. Differences in kinematics and contact location likely contributed to altered mechanics with anatomic subjects presenting greater load transfer from the quadriceps to the patellar tendon in deep flexion (>75°), and dome subjects demonstrating larger contact forces during lunge. Although there was substantial patient variability, evaluations of PF mechanics suggested improved quadriceps function and more natural kinematics in the anatomic design. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1910–1918, 2018.

     

Patellar tracking measurement in the normal knee

Eleven fresh frozen cadaveric knee specimens were mounted in a knee kinematics test device, and normal patellar movements were evaluated with use of an external device for direct measurement of patellar movements. The effects of four different measurement conditions were assessed through alteration of one condition and determination of its effect on patellar kinematics with the use of six specimens. The four conditions included (a) change of the measuring axis from an axis parallel to the central axis of the femur (femoral axis) to one parallel to the central axis of the tibia (tibial axis), (b) rotation of the femoral axis internally 6°, (c) change of the direction of the quadriceps force from parallel to the mechanical line of the lower extremity to a direction parallel to the femoral shaft, and (d) increase of the magnitude of the quadriceps force from 111 to 500 N. During knee flexion, the patella shifted laterally after a slight initial medial shift, tilted laterally from midflexion to 90°, and gradually rotated medially. The patellar shift relative to the tibial axis appeared to be more medial than the shift measured relative to the femoral axis; the discrepancy was caused by the valgus position of the tibia relative to the femur. Changing the rotational angle of the femoral axis artifically changed the patellar position. Varying the direction of the quadriceps within the narrow range and increasing the quadriceps force did not affect patellar movements. It is likely that the anatomic configuration of the patella allows the patella to seat in a stable configuration so that it resists moderate changes in the load and direction of the quadriceps. Tibial rotation exerted a major influence on patellar shift and tilt in the early phase of knee flexion: the patella rotated medially when the tibia was externally rotated and rotated laterally when the tibia was internally rotated. These results indicate that the patella may be unstable in the first phase of knee flexion when the tibia is rotated.     

Allogeneic Tendon Transplantation for the Treatment of Pathological Patellar Ligament Defect in Children: Technical Note and 4‐Year Follow‐Up

ObjectiveThe absence of patellar ligament will bring about a severe negative impact on daily life. Many reconstruction techniques have been described in adults. However, there is a lack of technical introduction regarding the reconstruction of the patellar ligament in children. The purpose of this study was to report a surgical technique for reconstructing the patellar ligament in children.MethodA retrospective analysis of the clinical data on a patellar ligament (tendon sheath fibroma) patient with allogeneic tendon reconstruction. An 8‐year‐old child with postoperative recurrence of left patellar ligament tumor was enrolled in our study. Anterior tibialis tendon allograft was used to reconstruct the patellar ligament after complete resection of the patellar ligament for the tumor. The tunnels were constructed on the deep surface of the tibial tubercle and the root of the quadriceps tendon (to decrease the harmful impact on patella development), respectively. The allogeneic tendon was passed through the tunnels above in the shape of “8,” and the two ends of the tendon were attached to the bleeding bone bed at the inferior edge of the patella with suture anchors to achieve better bone‐tendon healing. During the follow‐up, the knee''s range of motion and imaging manifestations were recorded.ResultPostoperative pathology suggests chondromesenchymal hamartoma, a rare benign soft tissue tumor different from the previous operation (tendon sheath fibroma). During the 4‐year follow‐up, the patient''s active range of motion of the knee achieved 0° to 120°; and the patient could walk normally without any external help. Physical examinations (the apprehension sign and J sign) showed no ligamentous instability or patellar ligament tenderness. Imaging analysis showed that the ratio length of the patellar ligament to the patella was almost normal. The integrity, continuity, and shape of the allogeneic ligament showed excellent results in MRI. Combined with clinical and imaging findings, allogeneic tendon patellar ligament reconstruction was deemed successful.ConclusionAllogeneic ligament reconstruction technique can provide a treatment option by reconstructing the extensor mechanism, minimizing the impact on patellar development, and augmenting biological healing for children with the absence of the patellar ligament.     

Failure of the Patellar Tendon with the Patella Everted versus Noneverted in a Matched-Pair Cadaver Model

Avoidance of patellar eversion during total knee arthroplasty may help to prevent injury to the patellar tendon. The purpose of this study was to compare the load-to-failure of the everted versus the noneverted patella in a cadaveric model. Fourteen cadaver knees (seven pairs) were loaded to failure with the patella everted in one knee and not everted in the other. Mean load-at-ultimate failure in the patella-everted group was 1,111 ± 572 N, and in the patella-noneverted group was 1,621 ± 683 N (p = 0.01). Additionally, loads-at-initial-partial failure were lower (p = 0.04) in the patella-everted compared to the patella-noneverted group, 573 ± 302 N versus 1,115 ± 358 N, respectively. A partial failure of the patellar tendon occurred in 100% of the everted specimens, whereas only 57% of the noneverted specimens had partial failure. These findings suggest patella eversion may lead to failure of the patellar insertion at lower loads than when the patella is not everted.     

The effect of an augmentation patella prosthesis versus patelloplasty on revision patellar kinematics and quadriceps tendon force: an ex vivo study

The purpose of this study was to assess the effect of 2 revision reconstructive interventions on patellofemoral joint mechanics in comparison to control. We flexed 8 cadaver knee specimens from 0 degrees to 60 degrees of flexion in a test rig designed to simulate weight-bearing flexion and extension (Oxford rig). Quadriceps tendon extensor force and patellar kinematics were recorded for control total knee arthroplasty (TKA) (normal primary TKA with patella resurfaced) and then for each of the 2 revision patellar interventions (after patelloplasty of typical revision knee patellar bone defect to leave a simple bony shell, and after TKA with augmentation patella resurfacing). Our results demonstrate that patellar kinematics and quadriceps extensor force are optimized when the patella is reconstructed to normal anteroposterior thickness.     

Effects of patellar position and defect healing on in vitro stifle joint kinematics following removal of the central one‐third of the patellar tendon in an ovine model

Harvest of the central one‐third of the patella tendon (PT) is routinely performed for anterior cruciate ligament reconstruction (ACLR). Patella infera may ensue. In this study we unilaterally resected the central one‐third of the PT in 20 sheep, without reconstructing or defunctionalizing the native ACL, and examined the effects at 3, 6, 12, and 24 weeks postoperatively on PT length, histological appearance of the donor defect and in vitro stifle joint kinematics. Mean length increases (p > 0.263) in the operated tendons of 0.3%, 2.8%, 0.5%, and 2.4% were observed at 3, 6, 12, and 24 weeks. A significant proximal shift of the patella correlated well with a mean 2.35° retardation of patellar flexion (r = 0.440, p = 0.001). A mean net 4.9° decrease in medial patellar tilt was also observed (p < 0.001), but was not coupled with changes in tibial rotation. Donor defect tissue showed a distinct progression of healing with time, remodeling from dense scar tissue at 3 weeks to bundles of well‐organized collagen enveloped by vascularized loose connective tissue at 24 weeks but was not associated with the restoration of kinematics. These results suggest that resection of the central one‐third of the PT and leaving the defect open in the ovine stifle joint may be associated with increased PT length and changes in patellar kinematics which do not recover 6 months postoperatively. The lack of patella infera may render this animal model unsuitable for the interpretation of joint kinematics following PT resection for human ACLR. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:572–581, 2011     

Model predictions of increased knee joint loading in regions of thinner articular cartilage after patellar tendon adhesion

Patellar tendon adhesion is a complication from anterior cruciate ligament (ACL) reconstruction that may affect patellofemoral and tibiofemoral biomechanics. A computational model was used to investigate the changes in knee joint mechanics due to patellar tendon adhesion under normal physiological loading during gait. The calculations showed that patellar tendon adhesion up to the level of the anterior tibial plateau led to patellar infera, increased patellar flexion, and increased anterior tibial translation. These kinematic changes were associated with increased patellar contact force, a distal shift in peak patellar contact pressure, a posterior shift in peak tibial contact pressure, and increased peak tangential contact sliding distance over one gait cycle (i.e., contact slip). Postadhesion, patellar and tibial contact locations corresponded to regions of thinner cartilage. The predicted distal shift in patellar contact was in contrast to other patellar infera studies. Average patellar and tibial cartilage pressure did not change significantly following patellar tendon adhesion; however, peak medial tibial pressure increased. These results suggest that changes in peak tibial cartilage pressure, contact slip, and the migration of contact to regions of thinner cartilage are associated with patellar tendon adhesion and may be responsible for initiating patellofemoral pain and knee joint structural damage observed following ACL reconstruction. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1168–1177, 2011     

In‐vivo patellar tracking in individuals with patellofemoral pain and healthy individuals

Understanding of the exact cause of patellofemoral pain has been limited by methodological challenges to evaluate in‐vivo joint motion. This study compared six degree‐of‐freedom patellar motion during a dynamic lunge task between individuals with patellofemoral pain and healthy individuals. Knee joints of eight females with patellofemoral pain and ten healthy females were imaged using a CT scanner in supine lying position, then by a dual‐orthogonal fluoroscope while they performed a lunge. To quantify patellar motion, the three‐dimensional models of the knee bones, reconstructed from CT scans, were registered on the fluoroscopy images using the Fluomotion registration software. At full knee extension, the patella was in a significantly laterally tilted (PFP: 11.77° ± 7.58° vs. healthy: 0.86° ± 4.90°; p = 0.002) and superiorly shifted (PFP: 17.49 ± 8.44 mm vs. healthy: 9.47 ± 6.16 mm, p = 0. 033) position in the patellofemoral pain group compared with the healthy group. There were also significant differences between the groups for patellar tilt at 45°, 60°, and 75° of knee flexion, and for superior‐inferior shift of the patella at 30° flexion (p ≤ 0.031). In the non‐weight‐bearing knee extended position, the patella was in a significantly laterally tilted position in the patellofemoral pain group (7.44° ± 6.53°) compared with the healthy group (0.71° ± 4.99°). These findings suggest the critical role of passive and active patellar stabilizers as potential causative factors for patellar malalignment/maltracking. Future studies should investigate the associations between patellar kinematics with joint morphology, muscle activity, and tendon function in a same sample for a thorough understanding of the causes of patellofemoral pain. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2193–2201, 2018.

     

关节镜下双束重建内侧髌股韧带联合半髌韧带内移治疗骨骺未闭合青少年复发性髌骨脱位

目的探讨关节镜下自体半腓骨长肌腱双束重建内侧髌股韧带联合半髌韧带内移手术治疗骨骺未闭合青少年复发性髌骨脱位的临床疗效。方法回顾性分析自2016-07—2018-09诊治的20例骨骺未闭合且胫骨结节-股骨滑车沟间距>20 mm的青少年复发性髌骨脱位,在关节镜下采用自体半腓骨长肌腱经大收肌肌腱止点悬吊双束重建内侧髌股韧带联合半髌韧带内移手术治疗。结果 20例均获得随访,随访时间平均21.2(12~36)个月。所有患者术后复查均未再发生髌骨脱位或半脱位,膝关节功能恢复满意。末次随访时髌股适合角为(-1.79±3.26)°,髌骨倾斜角为(11.11±1.08)°,较术前明显减小;末次随访时膝关节功能Lysholm评分为(94.60±2.58)分,髌股关节功能Kujala评分为(91.05±2.33)分,较术前明显提高,差异有统计学意义(P<0.05)。结论对于骨骺未闭合且胫骨结节-股骨滑车沟间距>20 mm的青少年复发性髌骨脱位患者,关节镜下采用自体半腓骨长肌腱双束重建内侧髌股韧带联合半髌韧带内移手术治疗可获得稳定的髌骨滑动轨迹,髌骨脱位矫正良好。     

Do surgical patellar interventions restore patellar kinematics in fixed-bearing,cruciate-retaining total knee arthroplasty? : An in vitro study

Despite different surgical patellar interventions, the decision how to treat the patella during TKA remains controversial. The purpose of this study was to quantify the effect of different reconstructive patellar interventions on patellar kinematics during TKA using optical computer navigation. We implanted ten navigated TKAs in full body specimens. During passive motion, the effect of different surgical patellar interventions on patellar kinematics was analysed. A contrarily tilt behaviour was observed in the TKA group without patellar intervention compared to the natural knee. Lateral release led to similar tilt values (P < 0.05). All surgical interventions led to a 3 to 5 mm medial shift of the patella (P < 0.05). None of the analysed surgical patellar interventions could restore natural patellar kinematics after TKA.     

Simulation of patella alta and the implications for in vitro patellar tracking in the ovine stifle joint

Patella alta is associated with adverse cartilage adaptations, patellofemoral pain, and instability. It is defined by a relatively long patellar tendon and patella positioned in a more proximal location within the patellar groove of the femur. This study used the ovine stifle joint model to investigate the effect of patellar tendon lengthening on the 3D passive kinematics of the patellofemoral and tibiofemoral joints. Eight patellar tendons were lengthened in 2 mm increments up to a maximum of 12 mm (20%) using a device placed in series with the transected patellar tendon. Three‐dimensional kinematics were measured in the intact joint and at each increment of patellar tendon length (L_T) during passively induced tibiofemoral flexion. Patellar flexion angle was linearly correlated with tibial flexion angle in the intact joint, and this correlation persisted after tendon lengthening (R = 0.897–0.965, p < 0.01). Patellofemoral kinematics expressed as a function of tibial flexion angle were significantly altered by L_T increases >9%. In contrast, when patellofemoral kinematics were expressed as a function of patellar flexion angle they were not significantly altered by increases in L_T. Tibiofemoral kinematics were not affected by the L_T increases. These results demonstrate that for a given tibial flexion angle, patellar tendon lengthening alters the patellar flexion angle. However, for a given patellar flexion angle, the orientation of the patella in the remaining five degrees of freedom is unchanged, implying a repeatable path of patellar motion. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1789–1797, 2012     

Patellar tendon length after knee arthroplasty with and without preservation of the infrapatellar fat pad

Our aim was to assess whether there was any significant difference in change in patellar tendon length after knee arthroplasty, when the infrapatellar fat pad was either preserved or excised. Three-year radiographic follow-up was studied on 73 primary knee arthroplasty patients. The infrapatellar fat pad was completely preserved in 38 cases and completely excised in 35. At 3 years there was a significant patellar tendon shortening of 4.2% (P = .0004) in the fat pad excision group and no significant change in the fat pad preservation group (P = .82). The difference between the 2 groups was significant (P = .004). Our results show that patella tendon length does not always shorten after knee arthroplasty and that preservation of the infrapatellar fat pad may be a factor in preventing such shortening.     

Reduced Bearing Excursion After Mobile-Bearing Unicompartmental Knee Arthroplasty is Associated With Poor Functional Outcomes

Background

A small proportion of patients with mobile unicompartmental knee arthroplasty (UKA) report poor functional outcomes in spite of optimal component alignment on postoperative radiographs. The purpose of this study is to assess whether there is a correlation between functional outcome and knee kinematics.

Neglected patellar tendon rupture: a case of reconstruction without quadriceps lengthening

Neglected rupture of the patellar tendon is a rare, can be easily missed in a group of patients. We present a 24 year old, male patient who sustained right femoral diaphyseal and tibial plateau fractures and a patellar tendon rupture following a motor vehicle accident. The fractures were treated by open reduction internal fixation but the patellar tendon rupture was missed and the diagnosis was delayed by 7 months. Patella was migrated proximally. It was moved distally to the original location and neglected patellar tendon rupture treated successfully with modified Ecker technique. Neither preoperative traction nor additional intraoperative procedures were performed to relocate the patella to its anatomic position in the extended knee and good functional result was achieved with intensive rehabilitation.     

The Effect of Medial Release of the Distal Patellar Tendon Insertion on Lateral Patella Translation and Residual Insertion Strength: A Cadaveric Study

Patellar tendon avulsion is a risk with difficult exposure in a stiff knee, patella baja or previous tibial osteotomy. We sought to define a safe amount of release of the patellar tendon insertion for such cases. Eleven pairs of fresh frozen cadaveric lower limb specimens were acquired and randomized to either intact or partial release of the distal tibial insertion. Partial release of the tibial insertion of the tendon increased lateral exposure a mean 29% ± 15% (P = 0.002) while reducing ultimate strength to a mean of 80% that of the intact contralateral tendon. Measured patella release increased lateral patella translation and can be performed without risk of catastrophic rupture with basic activities of daily living following TKA.     

Fixed‐bearing medial unicompartmental knee arthroplasty restores neither the medial pivoting behavior nor the ligament forces of the intact knee in passive flexion

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non‐conforming, fixed bearing medial UKA affects tibiofemoral kinematics, and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior–posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° of flexion, but occurred from 30° to 90° of flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non‐conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1868–1875, 2018.

     

In Vivo Knee Kinematics for a Cruciate Sacrificing Total Knee Arthroplasty Having Both a Symmetrical Femoral and Tibial Component

BackgroundEarly total knee arthroplasty (TKA) designs were symmetrical, but lead to complications due to over-constraint leading to loosening and poor flexion. Next-generation TKAs have been designed to include asymmetry, pertaining to the trochlear groove, femoral condylar shapes, and/or the tibial component. More recently, an advanced posterior cruciate sacrificing (PCS) TKA was designed to include both a symmetrical femoral component with a patented V-shaped trochlear groove and a symmetrical tibial component with an ultracongruent insert, in an attempt to reduce inventory costs. Because previous PCS TKA designs produced variable results, the objective of this study is to determine and evaluate the in vivo kinematics for subjects implanted with this symmetrical TKA.MethodsTwenty-one subjects, implanted with symmetrical PCS fixed-bearing TKA, were asked to perform a weight-bearing deep knee bend (DKB) while under fluoroscopic surveillance. A 3-dimensional to 2-dimensional registration technique was used to determine each subject’s anteroposterior translation of lateral and medial femoral condyles as well as tibiofemoral axial rotation and their weight-bearing knee flexion.ResultsDuring the DKB, the average active maximum weight-bearing flexion was 111.7° ± 13.3°. On average, from full extension to maximum knee flexion, subjects experienced −2.5 ± 2.0 mm of posterior femoral rollback of the lateral condyle and 2.5 ± 2.2 mm of medial condyle motion in the anterior direction. This medial condyle motion was consistent for the majority of the subjects, with the lateral condyle exhibiting rollback from 0° to 60° of flexion and then experienced an average anterior motion of 0.3 mm from 60° to 90° of knee flexion. On average, the subjects in this study experienced 6.6°± 3.3° of axial rotation, with most of the rotation occurring in early flexion, averaging 4.9°.ConclusionAlthough subjects in this study were implanted with a symmetrical PCS TKA, they did experience femoral rollback of the lateral condyle and a normal-like pattern of axial rotation, although less in magnitude than the normal knee. The normal axial rotation pattern occurred because the lateral condyle rolled in the posterior direction, while the medial condyle moved in the anterior direction. Interestingly, the magnitude of posterior femoral rollback and axial rotation for subjects in this study was similar in magnitude reported in previous studies pertaining to asymmetrical TKA designs. It is proposed that more patients be analyzed having this TKA implanted by other surgeons.