Computerized tomography of the patellofemoral joint before and after lateral release or realignment

Delayed proximal repair and distal realignment after patellar dislocation

Twenty athletes with distal malalignment who sustained unilateral traumatic patellar dislocation remained impaired by chronic instability. Surgery was performed at a mean age of 18 years. Posttraumatic attenuation of the medial patellofemoral ligament was repaired near the margin of the patella in 10 knees and avulsion or attenuation posterior to the vastus medialis obliquus in 10 knees. Advancement of the medial patellomeniscal ligament at the margin of the patella and normalization of the Q angle to 10 degrees by tibial tubercle osteotomy were performed in each knee. Distal lateral retinacular release without release of the normal vastus lateralis tendon was performed. Results were judged according to Turba et al, and activity levels were evaluated per guidelines of the International Knee Documentation Committee. Eighteen (90%) patients achieved good or excellent results and were unimpaired at a minimum of 24 months. Two patients achieved fair subjective results with some impairment in vigorous activity. There was no recurrent instability. Radiographically, the mean preoperative patellofemoral congruence angle improved from 20 degrees to 0 degree. Athletes who sustain an initial traumatic patellar dislocation after physeal closure and in whom conservative management fails can be treated successfully by repair of the medial patellofemoral ligament at the site of disruption and advancement of the medial patellomeniscal ligament combined with correction of an elevated Q angle.

Effect of bracing on patellar kinematics in patients with patellofemoral joint pain

PURPOSE

Bracing is commonly used to correct patellar malalignment syndromes. However, there are little objective data documenting the effect of such supports on patellofemoral joint relationships. The purpose of this study was to assess the effectiveness of an elastic patellofemoral sleeve brace in altering patellar tracking in subjects with patellofemoral pain.

METHODS

Ten female subjects (12 patellofemoral joints) between the ages of 17 and 46 participated in this study. All subjects had a diagnosis of patellofemoral pain and demonstrated lateral patellar tracking based on magnetic resonance imaging (MRI) assessment. Each subject underwent kinematic MRI of the patellofemoral joint through a range of 45 to 0 degrees of knee flexion against a resistance of 15% body weight. Imaging was performed with and without a patellofemoral joint brace (Bauerfeind Genutrain P3 brace, Atlanta, GA). Measurement of medial/lateral patellar displacement, medial/lateral patellar tilt, and the depth of the trochlear groove (sulcus angle) were obtained with midpatellar image sections at 45, 36, 27, 18, 9 and 0 degrees of knee flexion.

RESULTS

No statistically significant differences in medial/lateral patellar displacement or tilt were found between braced and unbraced trials across all knee flexion angles (P < 0.05). A small but statistically significant increase in sulcus angle was found across all knee flexion angles with the braced trials (P > 0.05).

CONCLUSIONS

These results do not support the hypothesis that the brace used in this study corrects patellar tracking patterns in subjects with patellofemoral pain. However, the increased sulcus angle indicates a change in patella position within the trochlea. It is possible that the clinical improvements seen with bracing may be the result of subtle differences in joint mechanics and not gross changes in alignment.

Axial and lateral radiographs in evaluating patellofemoral malalignment

This is a prospective study of 431 patients (862 knees) with patellofemoral pain, patellar dislocation, or other abnormalities of the knee joint. There were 217 asymptomatic knees with no contralateral problems for comparison. All patients had a history and physical and radiographic examination of both knees. The radiographs included standard anteroposterior views, axial views at 30 degrees of knee flexion, and standing lateral views at 0 degree and 30 degrees of flexion. The presence of patellar tilt or subluxation was noted on the axial view. The lateral view of the patella, with precise overlap of the posterior femoral condyles, allowed determination of relationships between the patella's medial edge, median ridge, and lateral edge to assess patellar tilt. Sixty-two percent of patients with patellar dislocations demonstrated subluxation on the axial view, while 98% demonstrated an abnormal lateral view. Eighteen percent of the control knees revealed evidence of subluxation on the axial view while 35% demonstrated subluxation on the extended lateral view. The axial view demonstrated 62% sensitivity for dislocation, while the lateral view taken in full extension demonstrated 98% sensitivity. The specificity for previous dislocation was 82% for the axial view and 93% for the lateral flexed view. Given the high sensitivity of the lateral view for detecting prior patellar dislocation, a normal result on this view can virtually eliminate the question of previous dislocation. Also, with the high specificity of the axial view and lateral view with knee flexion, the two views combined can confirm a clinical impression of patellofemoral malalignment.

The effects of axial and multi-plane loading of the extensor mechanism on the patellofemoral joint

OBJECTIVE: To compare the effects of axial loading, and anatomically based multi-plane loading of the extensor mechanism on the patellofemoral joint. DESIGN: Repeated measures design using an in-vitro cadaver model. BACKGROUND: Since the extensor mechanism is the primary contributor to the patellofemoral joint reaction force and can affect patellar kinematics, it is essential that the forces produced by this musculature be accurately represented in a simulation model. METHODS: Patellar kinematics (magnetic tracking device), contact pressures and areas (pressure sensitive film) were measured from 6 cadaver knees under two different loading conditions: 1) axial (rectus femoris loaded in the frontal plane), and 2) multiplane (individual components of the quadriceps loaded along their respective fiber directions in both the frontal and sagittal planes). Specimens were mounted in a custom knee jig, with muscle forces being simulated using a pulley system and weight. Data were collected at 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees of knee flexion. RESULTS: Compared to the axial loading condition, multi-plane loading of the vasti resulted in significantly greater contact pressure at 0 degrees and significantly less contact pressure at 90 degrees of knee flexion. Furthermore, the multi-plane loading condition resulted in greater lateral patellar rotation from 0-75 degrees of knee flexion, and greater lateral glide at 30 degrees of knee flexion. Greater patellar flexion was observed with the axial loading condition. CONCLUSIONS: These findings indicate that axial loading of the extensor mechanism underestimates contact pressure at 0 degrees and overestimates contact pressure at 90 degrees of knee flexion when compared to multi-plane loading. Additionally, loading of the individual vasti appears to have an effect on patellar kinematics. RELEVANCE: The results of this study indicate that anatomically based, multi-plane loading of the vasti will yield subtle yet significant differences in patellofemoral joint mechanics when compared to the more traditional axial loading approach. These differences may have implications for the study of both normal and pathological patellofemoral joint mechanics, as well as evaluation of surgical techniques and prosthetic implants.

Patellar alignment evaluated by MRI

We analyzed the congruence of the articular cartilage surfaces and the corresponding subchondral bone in the patellar joint. 20 volunteers underwent MRI investigations of the right patellar joint in 20 degree and 45 degree flexion in the axial plane. The sulcus, congruence, and lateral patellofemoral angles, measured on MRI slices centered through the midtransverse patella, were recorded. In 20 degree and 45 degree knee flexion, the bony sulcus and lateral patellofemoral angles were significantly different from the respective cartilagineous angle. We conclude that 1) measurement of the bony sulcus and lateral patellofemoral angles does not allow conclusions about the articular cartilage surface and its thickness, 2) the bony congruence angle corresponds well to the articular cartilage surface as an indicator of patellar centralization.

Quantification of patellar tracking using kinematic MRI

The purpose of this study was to describe a method to quantify dynamic patellar tracking using kinematic MRI (KMRI). Twelve normal females and three patients with patellofemoral pain participated. Imaging was performed with a 1.5-T/64-MHz MR system using a fast spoiled gradient-recalled acquisition in the steady state (GRASS) pulse sequence. A nonferromagnetic positioning device permitted active, bilateral knee extension against resistance (15% bwt) from 45 degrees knee flexion to full extension. Subjects were instructed to extend their knees at a rate of 9 degrees per second, which allowed images to be obtained at 45 degrees, 36 degrees, 27 degrees, 18 degrees, 9 degrees, and 0 degrees. All images were assessed for medial/lateral patellar displacement, patellar tilt, and sulcus angle using a computer-aided system. Normal patellar motion was characterized by medial movement from 45 degrees to 18 degrees, followed by a reversal toward lateral displacement from 18 degrees to full extension. The results for patellar tilt revealed a tendency toward decreasing lateral tilt as the knee extended. Sulcus angle measurements indicated that the patella was moving to a more shallow portion of the trochlear groove (superiorly) during extension.

Lateral release and proximal realignment for patellofemoral malalignment. A prospective study of 40 knees in 36 adolescents followed for 1-8 years

We performed lateral release and proximal realignment for painful patellofemoral malalignment in 36 adolescents (40 knees), with a mean age of 14 (9-16) years. The mean follow-up was 4 (1-8) years. The subjective outcome was excellent in 20 knees, good in 13, fair in 5, and poor in 2. The mean radiographic correction of the lateral patellar shift was 75%, and of the tilting angle of the patellar 27%. There was a positive association between the realignment effect and the subjective outcome.

Soft tissue restraints to lateral patellar translation in the human knee

The purpose of this investigation was to identify and quantify the soft tissue restraints, both medially and laterally, to lateral patellar translation. These restraints to lateral patellar translation at 20 degrees of knee flexion were tested biomechanically on a universal testing instrument in nine fresh-frozen cadaveric knees. After preconditioning the tissues, the patella of each intact knee was translated laterally to a distance at which a force of 200 N was recorded. This distance was used to translate the patella for the remaining structures to be sectioned. The contribution of each structure to the total restraining force was determined as the percent of the force to restrain the intact specimen by sectioning the restraints in a predetermined order. The contribution of each structure to the restraining force was defined as the difference between the restraining force before and after its sectioning. The medial patellofemoral ligament was found to be the primary restraint to lateral patellar translation at 20 degrees of flexion, contributing 60% of the total restraining force. The medial patellomeniscal ligament contributed 13% of the total force, and the lateral retinaculum contributed 10%. The medial patellotibial ligament and superficial fibers of the medial retinaculum were not functionally important in preventing lateral translation. The previously unrecognized contribution of the lateral retinaculum as a restraint to lateral patellar translation may shed new light on the failures of isolated lateral release for acute lateral dislocation of the patella.

Knee version associated with anterior knee pain

Version of the knee in the presence and absence of anterior knee pain was evaluated by computed tomography in this study. Version of the knee is defined as the static rotation of the tibia with respect to the femur in full knee extension. Fourteen patients in whom conservative management for anterior knee pain failed were compared with 14 volunteers with no symptoms. Computed tomography images of the femoral condyles and tibial plateau were obtained with the knee extended. The angle between the bicondylar and posterior tibial axes was measured. This angle, representing external rotation of the tibia relative to the femur, was increased significantly in patients with symptoms (7 degrees) compared with volunteers with no symptoms (1 degree). This increased knee version identifies a unique morphologic characteristic of the knee with anterior pain.

Anteromedial tibial tubercle transfer in patients with chronic anterior knee pain and a subluxation-type patellar malalignment

We performed a prospective analysis of 29 Fulkerson anteromedial tibial tubercle transfers in patients with chronic anterior knee pain. The average followup was 32 months (range, 25 to 44). Fourteen patients (Group 1) had subluxation-type malalignment (congruence angle > 20 degrees, tilt angle > 8 degrees) and were treated with an isolated anteromedial tibial tubercle transfer. Fifteen patients (Group 2) had combined subluxation and tilt malalignment (congruence angle > 20 degrees, tilt angle < 8 degrees) and underwent anteromedial tibial tubercle transfer combined with a lateral release. Pre- and postoperative evaluations included clinical and radiographic examinations, Lysholm and Kujala patellofemoral scores, and standing-alignment computed tomography scans in 15 degrees of flexion taken transversely at the midpatellar. In all but one patient a dramatic improvement in Lysholm and Kujala scores was noted. The congruence angle improved in all patients except one, with an average improvement of 16 degrees in Group 1 and of 14 degrees in Group 2. The tilt angle remained relatively unchanged (change, -0.5 degree) in Group 1, but it improved by 11 degrees in Group 2. We conclude that an isolated anteromedial tibial tubercle transfer can consistently improve patellar subluxation and, when combined with a lateral release, can improve patellar subluxation and tilt, resulting in improved functional scores for patients with chronic anterior knee pain.

Axial radiography or CT in the measurement of patellofemoral malalignment indices in children and adolescents?

The present study compares the repeatability of patellofemoral malalignment (PFM) indices obtained by 20 degree flexion axial radiography (AR) and computerized tomography (CT) with 0 degree and 20 degree flexion of the knees in children and adolescents. Thirty-one patients with a mean age of 14.2 years (range 8 to 19.2 years) suffering from PFM were examined using these two radiographic techniques. The lateral patellofemoral angle (LPA), the lateral patellar tilt (LPT), and the lateral patellar displacement (LPD) were measured by by two different investigators on different occasions, and the agreement of these indices between CT and AR was evaluated according to Bland and Altman's statistical method. LPT and LPD obtained by AR were more reliable and repeatable than those obtained by CT. The quadriceps muscle contraction exacerbates PFM indices significantly with the knees in full extension (P = 0.0001). LPT and LPD measured at 20 degrees AR show reliably the two pathological components (the patellar tilt and the lateral patellar displacement) of PFM which are necessary for diagnosis and treatment planning. CT with quadriceps contractions is better in qualitative screening of more subtle cases of PFM.

Patellar tilt and subluxation following subvastus and parapatellar approach in total knee arthroplasty. Implication for surgical technique

Eighty-nine posterior-stabilized total knee arthroplasties (TKAs) were studied using a Merchant view to assess patellar tilt or subluxation. Forty TKAs were performed via the subvastus approach (SVA) and 49 via the standard parapatellar approach (PPA). Intraoperative tracking was assessed using a "no thumbs" test, and a lateral release was performed if necessary. Following the SVA, 40.0% of patellas tracked centrally compared to 44.9% for the PPA. With the SVA, a lateral release was necessary in 27.5% of procedures compared to 51.0% for the PPA. The data suggest that the no thumbs test may overestimate the need for lateral release following the PPA. Since there are fewer lateral releases following the SVA, reapproximation of the medial retinaculum to assess intraoperative tracking may result in fewer lateral release being performed without adversely affecting patellar position. Medial tilting of the patella is also found to be common; 29.7% of the patellas tilted this way, including 40.0% of knees operated via the SVA. Why this occurs is unclear, but the incidence of medial tilting increased after posterior-stabilized TKA.

CT determination of tibial tubercle lateralization in patients presenting with anterior knee pain

Anterior knee pain is commonly associated with patellofemoral malalignment. Both conventional radiographic measurements and CT measurements have been proposed to define and confirm the sometimes difficult clinical diagnosis of anterior knee pain secondary to patellofemoral malalignment. Using CT imaging with computerized technique to measure anatomic relationships, we evaluated patients (n = 50) with anterior knee pain for excessive lateralization of the tibial tubercle. The symptomatic knee of each patient was compared with their asymptomatic knee as well as with the knees of patients with other causes of anterior knee pain (n = 10) and with the knees of asymptomatic controls (n = 10). The symptomatic knee of patients with suspected patellofemoral malalignment demonstrated significantly greater lateralization of the tibial tubercle (12.2 +/- 0.5 mm) than did the asymptomatic knee (9.0 +/- 0.7 mm). The symptomatic knees of patients with patellofemoral malalignment also demonstrated significantly greater lateralization of the tibial tubercle than did the knees of patients with other causes of anterior knee pain (5.9 +/- 0.9 mm). When a control population was added to the analysis, the patients with symptomatic patellofemoral malalignment demonstrated significantly greater lateralization of the tibial tubercle than did the controls (6.4 +/- 0.4 mm). Using a critical value of 9 mm lateralization, the CT diagnosis of patellofemoral malalignment had a specificity of 95% and a sensitivity of 85%. We conclude that CT determination of tibial tubercle position assists the diagnosis of patellofemoral malalignment.

Cine MR imaging before and after realignment surgery for patellar maltracking -- comparison with axial radiographs

OBJECTIVE

Comparison of motion-triggered cine magnetic resonance (MR) imaging and conventional radiographs for the assessment of operative results of patellar realignment.

SUBJECTS AND METHODS

Fifteen patients with recurrent patellar dislocation or patellar subluxation were evaluated with conventional axial radiographs before and after realignment surgery by measuring the congruence angle (CA), lateral patellofemoral angle (LPFA), and lateral displacement (d). In eight patients the patellofemoral joint was additionally evaluated pre- and postoperatively with motion-triggered cine MR imaging by determining the bisect offset (BSO), lateral patellar displacement (LPD), and patellar tilt angle (PTA).

RESULTS AND CONCLUSIONS

Significant differences between the pre- and postoperative measurements were found for all MR imaging parameters (BSO, LPD, PTA: p<0.01) but not for the conventional X-ray parameters (CA: p = 0.70, LPFA: p = 0.56; d: p = 0.04). Motion-triggered cine MR imaging was superior to conventional tangential radiographs for assessing the effectiveness of patellar realignment surgery.

A biomechanical comparison of lateral retinacular releases

A lateral patellar retinacular release that transects the tendon of the vastus lateralis muscle may result in significant complications. To avoid such complications, the superior extent must be limited, and maximizing the inferior extent may be important in achieving an adequate release. The effective release of the patella from its lateral retinaculum was examined for 2 incision lengths using 10 fresh-frozen human cadaveric knees and comparing the medial displacement of the patella relative to the femur for 3 study groups (control, intact retinacula; Group A, retinacula cut from the inferior third of the vastus lateralis tendon down to the anterolateral arthroscopic portal; and Group B, retinacula cut from the inferior third of the vastus lateralis tendon down to the tibial tubercle) when a 22-N medially directed force was applied to the patella with the knee at 30 degrees and 60 degrees of flexion. The extended release (Group B) resulted in a significantly more effective release when compared with the standard release (Group A) or control group. This technique may allow an adequate release of the patella while preserving the function of the vastus lateralis muscle.

Technical report: radiological evaluation of patellar malalignment using a new frame for axial imaging of the patellae

Axial radiographs were performed on 59 children and adolescent patients with patellar malalignment using the method described by Laurin. A special frame was used to keep the knees in 20 degrees flexion and to maintain standard conditions. Radiological indices were measured before realignment surgery. A statistically significant difference (P < 0.0001) in the lateral patellofemoral angle was observed comparing malaligned and control patellae. Laurin's technique using a special frame provides a method of obtaining standard radiological measurements of patellar malalignment for use in surgical planning.

Use of a modified Elmslie-Trillat procedure to improve abnormal patellar congruence angle

Forty patients underwent 45 modified Elmslie-Trillat realignment procedures (mean followup, 2 years) for refractory patellar instability (34 knees) or painful patellofemoral syndrome with malalignment (11 knees). The postoperative congruence angle (mean, +3.4 degrees) was significantly improved compared with the preoperative value (mean, +21.5 degrees). We considered the "normal" congruence angle average as -8 degrees (range, -20 degrees to +4 degrees). Over time postoperatively, we detected no statistical difference in the congruence angle (5 months, 3.4 degrees; 24 months, 6.3 degrees). There were no patellar dislocations postoperatively. Nine knees (20%) had some postoperative subluxation. Ninety-four percent of the patients without subluxation had congruence angles less than 15 degrees, whereas 54% of patients with postoperative subluxation had postoperative congruence angles greater than 15 degrees. The evidence in this study population indicates that the modified Elmslie-Trillat procedure can predictably improve the patellar congruence angle. Adequate correction may eliminate patellar dislocation. Correction of the congruence angle to less than +15 degrees will result in a decreased incidence of postoperative patellar instability. Early full activity postoperatively did not affect the modified Elmslie-Trillat correction of the congruence angle being maintained over time.

Patellofemoral Pain Disorders: Evaluation and Management

Patellofemoral pain disorders can be difficult to diagnose. Careful attention to the history and physical examination is central to accurate diagnosis. Standardized office radiographs are sufficient in most cases. Computed tomography of the patellofemoral joint (precise midpatellar transverse images through the posterior femoral condyles with the knee at 15, 30, and 45 degrees of knee flexion) will provide valuable objective information regarding subtle abnormalities of patellar alignment. Magnetic resonance imaging and radionuclide scanning may be helpful in selected cases. By differentiating between rotational (tilt) and translational (subluxation) components of patellar malalignment, the clinician will be better able to prescribe appropriate treatment. It is also extremely important to localize and quantitate articular and retinacular abnormalities. While nonoperative treatment is usually successful, surgery is sometimes required. Lateral release will relieve tilt and associated pain in the lateral retinaculum. Realignment of the extensor mechanism, usually at the level of the tibial tubercle, is necessary to control lateral tracking (subluxation) of the patella. If there is lateral or distal medial articular damage related to chronic lateral tilt and/or subluxation, shift of the tibial tubercle will help to unload damaged cartilage while realigning the extensor mechanism.

Lateral patellar instability: treatment with a combined open-arthroscopic approach

Lateral patellar maltracking, subluxation, and dislocation could arguably be grouped together as varying degrees of lateral patellar instability. Besides common anatomical etiological factors, such as genu valgum, patella alta, tibial rotation, and others, the author has found that many of these patients exhibit patellar hypermobility, a seldom mentioned physical finding. Lateral retinacular release fails to address the hypermobility, whereas traditional, more extensive open operations often carry significant postoperative morbidity and disability. This article suggests a surgical approach that combines open medial tethering of the patellar tendon with arthroscopic lateral release. The procedure addresses both etiological factors of anatomical peculiarity and patellar hypermobility, with a relatively benign postoperative course. In a series of 29 cases with follow-up of 4-8 years, results appear encouraging so far.

Magnetic resonance imaging of patellofemoral relationships

Patellofemoral relationships were analyzed in 11 patients (13 knees) with patellar dislocation and 15 asymptomatic subjects (15 knees) at 0 degree and 20 degrees of flexion. The measurements were made from five consecutive axial images through the patellofemoral joint. The six indices measured were lateral patellar tilt (LPT), lateral patellofemoral angle (LPA), lateral patellar displacement (LPD), patella-lateral condyle index (L/PW), congruence angle (CA), and sulcus angle (SA). The reproducibility of the method was evaluated. The difference between the two study groups was more evident at 0 degree than at 20 degrees of knee flexion. Significant differences were noted between measurements made at different levels of the joint, particularly in the controls. Isometric contraction of the quadriceps muscle lateralized and tilted the patella slightly in both groups. L/PW with and without quadriceps muscle contraction, and LPA with reference to the anterior condyles differentiated between the two study groups most clearly. LPT and LPA with reference to the anterior condyles differentiated the study groups better than LPT and LPA with reference to the posterior condyles. The reproducibility was good except for inter-observer comparison of CA and SA. The use of an imaging plane selected at the midpoint of the patellar articular cartilage increases the sensitivity of the measurements, since it takes into account both the height of the patella and the tendency towards lateralization. These results indicate that patellar tilt is best measured with the LPA index and patellar lateralization with the L/PW index at 0 degree knee flexion. This study should always include isometric contraction of the quadriceps muscle.

Patellofemoral relationships and distal insertion of the vastus medialis muscle: a magnetic resonance imaging study in nonsymptomatic subjects and in patients with patellar dislocation

The correlation between the insertion level of the vastus medialis muscle and lateral patellofemoral angle (LPA), lateral patellar displacement (LPD) and tilt (LPT), and the height of the patella (LT/LP) was analyzed by magnetic resonance imaging (MRI) in patients with patellar dislocation (n = 10) and in control subjects (n = 10). Images were produced in 0 degrees and 20 degrees of knee flexion. The insertion level to the patella was also analyzed with the knee in extension. No significant correlation was noted between the insertion level and different patellofemoral indexes, but multiple-regression analysis showed that the best predictor for the insertion level was the LPA with the knee in extension. The insertion level was significantly more proximal in patients with patellar dislocations than in normal subjects.

Lateral retinacular release for patellofemoral pain in the older patient

Lateral release for patellofemoral pain was performed on 39 knees in 34 patients aged greater than or equal to 30 years. At a mean follow-up of 6 years, there were 56% good or excellent results. Only 20% of patients did not achieve any benefit from the procedure. Although these results may not be as good as in the younger patient, this low morbidity procedure is nevertheless useful in the management of the older patient with patellofemoral malalignment.

Innervation of the human knee joint by substance-P fibers

Anterior knee pain is a frequent musculoskeletal complaint affecting all ages, both sexes, athletes, and nonathletes alike. Numerous theories have been proposed regarding its etiology including patellar malalignment, quadriceps insufficiency, subluxation, quadriceps muscle tightness, and chondral defects. However, the mechanism by which these factors produce this pain is not clear. Knowledge of the distribution of nociceptive nerve fibers around the knee would seem to provide insight in treating these painful conditions. Eleven human patellae--eight specimens from patients with degenerative patellofemoral disease and three normals--were evaluated. Immunohistochemical techniques using monoclonal antibody to substance-P were employed to identify nociceptive fibers. Substance-P is a nociceptive neurotransmitter found in afferent nerve fibers. Substance-P fibers were isolated in the retinaculum, fat pad, periosteum, and subchondral plate of patellae affected with degenerative disease. This study demonstrates that selective tracting of nociceptive pain fibers is possible around the knee both in soft tissue and, in some circumstances, bone. The subchondral plate of normal patellae did not demonstrate erosion channels, but those with chondral defects from degenerative disease did. Nociceptive fibers found in these defects may explain the origin of symptoms in some patients. The distribution of substance-P nerve fibers in the soft tissues around the knee suggests that denervation may be the mechanism by which surgical procedures for anterior knee pain produce favorable results.

Anteromedial tibial tubercle transfer without bone graft

We followed 30 patients for more than 2 years after anteromedial tibial tubercle transfer for persistent patellofemoral pain associated with patellar articular degeneration. Twelve of these patients were followed more than 5 years. We report 93% good and excellent results subjectively and 89% good and excellent results objectively. The quality of improvement was sustained in all 12 of the patients who were evaluated again after more than 5 years from surgery. When examined separately, 75% of those patients with advanced patellar arthrosis achieved a good result; none of these patients achieved an excellent result. Postoperative continuous passive motion has markedly reduced the incidence of stiffness. Serious complications such as compartment syndrome, infection, and skin slough were avoided completely in 51 consecutive cases. Patellofemoral contact pressure studies in five cadaver knees have shown that anteromedial tibial tubercle transfer can provide substantial reduction of patellofemoral contact stress while helping to balance medial and lateral facet pressures. This surgical procedure is mechanically and clinically successful for alleviating intractable pain related to patellar malalignment and articular degeneration. This procedure enables the majority of appropriately selected patients with malalignment and patellar articular degeneration to resume increased levels of activity with substantially diminished pain.

Arthroscopic lateral release for patellar pain or instability

Forty-five arthroscopic lateral releases were reviewed with a follow-up from 2 to 6 years (average 4 years). Satisfactory results were obtained in 60% of the patellar pain group (20 knees) and 68.5% of the instability group (19 knees). The results in osteoarthrosis (6 knees) were unsatisfactory. Postoperative hemarthrosis was infrequent (2.2%). Unfavorable prognostic factors are an incomplete release with an insufficient postoperative passive patellar tilt in the pain group and more than five preoperative dislocations in the instability group. After failure of conservative treatment, a lateral release can be reasonably used in pain syndromes with a tight lateral retinaculum and lateral patellar tracking and in milder cases of instability.