Patellofemoral Instability: Evaluation and Management

A CURRENT REVIEW ON THE BIOLOGY AND TREATMENT OF ARTICULAR CARTILAGE DEFECTS (PART I & PART II)

Osteochondral injury occurs predominantly in physically active young adult males. Injury to the articular cartilage and/or subchondral bone may not only cause acute joint disease resulting in osseous intracapsular (synovitis) or extracapsular pain, but may also act to spawn arthritic conditions in later life. Since the 18th century, such injury has proven difficult to treat clinically, and much therapy has been essentially palliative. Past treatments such as abrasion arthroplasty, drilling, microfracture and arthroscopic lavage have been useful in removing articular debris and promoting the formation of the fibrin clot used in most native repair mechanisms. However, the limitation of these techniques is their inability to restore the damaged cartilage and subchondral bone to their normal tissue architecture. Recent developments in tissue engineering have concentrated on the utilization of autologous chondrocyte implantation, biomaterials and growth factors to promote the regeneration of biomechanically superior hyaline articular cartilage. This paper reviews the etiology, repair biology and therapeutic techniques of cartilage and/or osteochondral injury over the previous decades, and attempts to provide insight into interesting new research directions which offer much potential for improved treatment of these troublesome lesions.

Surgical versus non-surgical interventions for treating patellar dislocation

BACKGROUND

Patellar dislocation occurs when the patella disengages completely from the trochlear (femoral) groove. Following reduction of the dislocation, conservative rehabilitation with physiotherapy may be used. Since recurrence of dislocation is common, some surgeons have advocated surgical intervention in addition to rehabilitation.

OBJECTIVES

The purpose of this review was to assess the clinical and radiological outcomes of surgical, compared with non-surgical, interventions for treating people with primary or recurrent patellar dislocation.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group's Specialised Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library), MEDLINE, EMBASE, AMED, CINAHL, ZETOC, Physiotherapy Evidence Database (PEDro), and a variety of other literature databases and trial registries. Corresponding authors were contacted to identify additional studies. Date searched: August 2010.

SELECTION CRITERIA

Eligible for inclusion were randomised and quasi-randomised controlled clinical trials evaluating surgical versus non-surgical interventions for treating lateral patellar dislocation.

DATA COLLECTION AND ANALYSIS

Two reviewers independently examined titles and abstracts of each identified study to assess study eligibility, extract data and assess risk of bias. Primary outcomes assessed were the frequency of recurrent dislocation, and validated patient-rated knee or physical function scores. When appropriate, data were pooled. Risk ratios were calculated for dichotomous outcomes, and mean differences for continuous outcomes.

MAIN RESULTS

Five studies (339 participants) were included. All studies had methodological shortcomings, especially the two quasi-randomised trials that presented a high risk for selection bias. Follow-up was a minimum of two years in two studies and between five and seven years in three studies. There was no significant difference between surgical and non-surgical management of primary (first-time) patellar dislocation in the risk of recurrent dislocation (47/182 versus 53/157; risk ratio 0.81, 95% confidence interval 0.56 to 1.17; 5 trials), Kujala patellofemoral disorder scores (mean difference 3.13, 95% confidence interval -7.34 to 13.59; 5 trials) nor the requirement for subsequent surgery (risk ratio 1.09, 95% CI 0.72 to 1.65; 3 trials). Adverse events were reported by one trial, citing four major complications that occurred in the surgical group. No randomised controlled trials have assessed populations with recurrent patellar dislocation.

AUTHORS' CONCLUSIONS

There is insufficient high quality evidence to confirm any significant difference in outcome between surgical or non-surgical initial management of people following primary patellar dislocation, and none examining this comparison in people with recurrent patellar dislocation. Adequately powered randomised, multi-centre controlled trials, conducted and reported to contemporary standards are recommended.

Comparison of quadriceps angle measurements using short-arm and long-arm goniometers: correlation with MRI

OBJECTIVE

To compare the reliability of quadriceps-angle (Q-angle) measurements performed using a short-arm goniometer and a long-arm goniometer and to assess the accuracy of goniometer-based Q-angle measurements compared with anatomic Q angles derived from magnetic resonance imaging (MRI).

DESIGN

An intra- and interobserver reliability study.

SETTING

University hospital.

PARTICIPANTS

Eighteen healthy subjects with no history of knee pain, trauma, or prior surgery were examined.

METHODS

Two physicians, blinded to subject identity, measured Q angles on both knees of all subjects using 2 goniometers: (1) a short-arm goniometer and (2) a long-arm goniometer. Q angles were derived from axial MRIs of the subjects' hip and knees.

MAIN OUTCOME MEASUREMENTS

The intra- and interobserver reliabilities of each goniometer were assessed using the intraclass correlation coefficient (ICC). The comparison between clinical and MRI-based Q angles was assessed by using the ICC and a paired t-test.

RESULTS

Intra- and interobserver reliabilities of the long-arm goniometer (intraobserver ICC, 0.92; interobserver ICC, 0.88) were better than those of the short-arm goniometer (intraobserver ICC, 0.78; interobserver ICC, 0.56). Although both goniometers measured Q angles that were moderately correlated to the MRI-based measurements (ICC, 0.40), the clinical Q angles were underestimated compared with the MRI-based anatomic Q angles (P < .05).

CONCLUSION

The results of this study suggest that, although reproducible Q-angle measurements can be performed using standardized patient positioning and a long-arm goniometer, methods to improve the accuracy of clinical Q-angle measurements are needed.

The EOS imaging system for understanding a patellofemoral disorder following THR

An aspect of patellofemoral syndrome secondary to total hip replacement (THR) is mainly suggestive of a problem of femoral implant torsion. We here present the first reported case of patellofemoral syndrome secondary to THR relating to limb-length discrepancy, with no abnormality of femoral torsion. The pelvis adapted to the length inequality by axial rotation rather than frontal tilt, and this went undetected on standard X-ray and CT-scan. 3D imaging in upright posture on the EOS system enabled the situation to be clearly described and analyzed, and adapted surgical correction to be indicated.

Outcome of surgery for recurrent patellar dislocation based on the distance of the tibial tuberosity to the trochlear groove

We evaluated the outcome in a series of patients with recurrent patellar dislocation who had either medial transfer of the tibial tuberosity and lateral release or an isolated lateral release as the primary treatment. The decision to use one or other procedure was based on a pre-operative distance between the tibial tuberosity to the trochlear groove (TTTG) of less than 10 mm to include the tibial tuberosity transfer in addition to the lateral release.

Between April 2002 and December 2006, 49 patients (63 knees) underwent one of these procedures. A total of 35 patients (46 knees) was evaluated at a mean of 38 months (13 to 71) post-operatively. Medial transfer of the tibial tuberosity was performed in 33 knees and isolated lateral release in the remaining 13. Evaluation included the International Knee Documentation Committee (IKDC), the Kujala and the Short-form 36 scores. From the tibial tuberosity group 23 knees also underwent radiological examination at follow-up.

There were further episodes of patellar dislocation in six of the 46 knees available for review. Further dislocation was noted in five of 33 knees (15.2%) in the tibial tuberosity transfer group and in one of 13 knees (7.7%) in the lateral release group. The mean subjective IKDC score was 80.4 (sd 11.6), the mean Kujala score 88 (sd 8.2) and the mean objective IKDC score was 79% normal and 21% nearly normal. The mean post-operative TTTG distance in the tibial tuberosity transfer group was 8.9 mm (3.2 to 15.7) compared with the mean pre-operative value of 16.8 mm (12.2 to 24.4).

Treatment of articular cartilage lesions of the knee

Treatment of articular cartilage lesions in the knee remains a challenge for the practising orthopaedic surgeon. A wide range of options are currently practised, ranging from conservative measures through various types of operations and, recently, use of growth factors and emerging gene therapy techniques. The end result of these methods is usually a fibrous repair tissue (fibrocartilage), which lacks the biomechanical characteristics of hyaline cartilage that are necessary to withstand the compressive forces distributed across the knee. The fibrocartilage generally deteriorates over time, resulting in a return of the original symptoms and occasionally reported progression to osteoarthritis. Our purpose in this study was to review the aetiology, pathogenesis and treatment options for articular cartilage lesions of the knee. At present, autologous cell therapies, growth factor techniques and biomaterials offer more promising avenues of research to find clinical answers.

In vivo strain of the medial vs. lateral quadriceps tendon in patellofemoral pain syndrome

Patellofemoral pain (PFP) is thought to be related to patellar maltracking due to imbalances in the knee extensor. However, no study has evaluated the in vivo biomechanical properties of the quadriceps tendon in PFP syndrome. Our purpose was to compare the biomechanical properties of the quadriceps tendons in vivo and noninvasively in patients with PFP syndrome to those of control subjects. The null hypothesis was that the quadriceps tendons of PFP subjects would have significantly decreased strain compared with control subjects. Fourteen subjects (7 control, 7 PFP) performed voluntary ramp isometric contractions to a range of torque levels, while quadriceps tendon elongation was measured using ultrasonography. Tendon strain was calculated for the vastus medialis obliquus (VMO) and vastus lateralis (VL) portion of the quadriceps tendon and compared between subjects (control vs. PFP) and within subjects (VMO vs. VL). PFP subjects showed significantly less VMO tendon strain than control subjects (P<0.001), but there was no difference in VL tendon strain between PFP and control subjects (P=0.100). Relative weakness of the VMO is the most likely cause of the decreased tendon strain seen in subjects with PFP. VMO weakness not only explains the decreased medial tendon strain but also explains the presence of increased lateral patellar translation and lateral patellar spin (distal pole rotates laterally) reported in the literature in this population. This technique can potentially be used in a clinical setting to evaluate quadriceps tendon properties and infer the presence of muscle weakness in PFP.

Conservative versus surgical treatment for repair of the medial patellofemoral ligament in acute dislocations of the patella

PURPOSE

The objective of this study was to analyze and compare the results obtained after 2 types of treatment, surgical and conservative, for acute patellar dislocations.

METHODS

We divided 33 patients with acute patellar dislocations into 2 groups. One group with 16 patients underwent conservative treatment (immobilization and subsequent physiotherapy), and the other group with 17 patients underwent surgical treatment. A radiographic examination was performed in the evaluation of the patients to verify predisposing factors for patellofemoral instability, and the Kujala questionnaire was applied with the intention of analyzing the improvement of pain and quality of life. The chi(2) test, t test, and Fisher test were used in the statistical evaluation. A significance level of P < .05 was adopted.

RESULTS

The groups were considered parametric in relation to age and sex. The conservative treatment group exhibited a higher number of recurrent dislocations (8 patients) than the surgical treatment group, which did not have any relapses. In addition, the surgical treatment group obtained a better mean score on the Kujala test (92) than the conservative treatment group (69).

CONCLUSIONS

We conclude that surgical treatment afforded better results. There were no recurrences in the surgical treatment group, but there were 8 recurrences in the conservative treatment group. The mean Kujala score was 92 in the surgical treatment group and 69 in the conservative treatment group.

LEVEL OF EVIDENCE

Level II, lesser-quality therapeutic randomized controlled trial.

In vivo noninvasive evaluation of abnormal patellar tracking during squatting in patients with patellofemoral pain

BACKGROUND

Patellofemoral pain syndrome is one of the most common knee problems and may be related to abnormal patellar tracking. Our purpose was to compare, in vivo and noninvasively, the patellar tracking patterns in symptomatic patients with patellofemoral pain and those in healthy subjects during squatting. We tested the hypothesis that patients with patellofemoral pain exhibit characteristic patterns of patellar tracking that are different from those of healthy subjects.

METHODS

Three-dimensional patellar kinematics were recorded in vivo with use of a custom-molded patellar clamp and an optoelectronic motion capture system in ten healthy subjects and nine subjects with patellofemoral pain. The position of osseous knee landmarks was digitized while subjects stood upright, and then patellofemoral kinematics were recorded during squatting. The tracking technique was validated with use of both in vitro and in vivo methodologies, and the average absolute error was <1.2 degrees and <1.1 mm.

RESULTS

At 90 degrees of knee flexion, the patella showed lateral spin (the distal pole of the patella rotated laterally) in subjects with patellofemoral pain (mean and standard deviation, -10.13 degrees +/- 2.24 degrees) and medial spin in healthy subjects (mean, 4.71 degrees +/- 1.17 degrees) (p < 0.001). At 90 degrees of knee flexion, the patella demonstrated significantly more lateral translation in subjects with patellofemoral pain (mean, 5.05 +/- 3.73 mm) than in healthy subjects (mean, -4.93 +/- 3.93 mm) (p < 0.001).

CONCLUSIONS

Kinematic differences between healthy subjects and subjects with patellofemoral pain were demonstrated through a large, dynamic range of knee flexion angles. Increased lateral patellar translation and lateral patellar spin in subjects with patellofemoral pain suggest that the patella is not adequately balanced during functional activities in this group. Prospective studies are needed to identify when patellofemoral pain-related changes begin to occur and to determine the risk for the development of patellofemoral pain in individuals with abnormal kinematics.

The reliability and validity of the Q-angle: a systematic review

The quadriceps or Q-angle is an index of the vector for the combined pull of the extensor mechanisms and the patellar tendon. It is used as an indicator for patellofemoral joint dysfunction. The purpose of this article is to systematically review and appraise the literature to determine the reliability and validity of this test. An electronic database search was performed accessing AMED, British Nursing Index, CINAHL, the Cochrane database, EMBASE, ovid Medline, Physiotherapy Evidence Database (PEDro), PsycINFO, Pubmed and Zetoc to April 2008. All English language, human subject, clinical trials, assessing the inter- or intra-tester reliability, or the criterion validity, were included. The Critical Appraisal Skills Programme appraisal tool was used to establish the methodological quality of each study. Ten articles including 569 control and 179 patellofemoral disorder knees were reviewed. The findings suggest that there is considerable disagreement on the reliability and validity of the clinical Q-angle measurement. This may be due to a lack of standardisation in the measurement procedure. Further study is advocated to re-evaluate this topic using well-designed, and sufficiently large observational studies of specific patellofemoral dysfunction populations.

Adolescent patellofemoral pain: implicating the medial patellofemoral ligament as the main pain generator

PURPOSE

The purpose of this study is to define the clinical presentation of adolescent patellofemoral pain.

METHODS

A review was completed of all patients with patellofemoral pain at a children's hospital sports clinic over a 3-year period.

RESULTS

One hundred and one patients (91 female) with 136 symptomatic knees were identified. Mean age was 14.4 years. Knee pain was localized to the anteromedial or anterior region of the knee in 96% of patients and was typically produced with running (94%), jumping (92%) and stair use (69%). On physical examination there was usually a non antalgic gait (99%), no patellofemoral crepitation (98%), normal lower extremity angular (84%) and rotational alignment (94%), with no foot malalignment (>97%). The medial patellofemoral ligament (MPFL) was the most palpably tender area of the knee in 98% of patients. During "lateral apprehension" testing, 89% had pain at the MPFL, but not true apprehension. A "J-sign" was present at terminal knee extension in 65%. Mean Q-angle was 18.7 degrees . Means of all radiographic measures were within normal ranges.

CONCLUSION

The prototypical patient had anterior/anteromedial knee pain of insidious onset during running and jumping. The most consistent physical findings were focal tenderness at the MPFL, positive terminal J-sign, and an elevated Q-angle. Most patients required only nonsurgical treatments, but 18% underwent surgical interventions for persistent pain.

An evaluation of the clinical tests and outcome measures used to assess patellar instability

A literature review was undertaken to determine which clinical tests and outcome measures have been described to diagnose and evaluate patellar instability, and to assess the literature examining the sensitivity and specificity of these diagnostic tests, or the reliability, validity and responsiveness of the outcome measures identified. An electronic search was undertaken using standard databases as well as a hand search of specialist journals, reference lists and local medical libraries. All English language publications describing and/or evaluating diagnostic tests and outcome measures for patellar instability patients were included. On review, 104 papers and 64 textbooks were included. Eighteen diagnostic tests and 10 outcome measures were identified. Of these only five diagnostic tests (Bassett's sign; apprehension test; gravity subluxation test; clinical assessment of the tibial tubercle to trochlear groove value; Q-angle) and seven outcome measures (modified International Knee Documentation Committee knee ligament standard evaluation form; Kujala anterior knee pain scale; Fulkerson knee instability scale; Lysholm knee scoring scale; Tegner activity level scale; Short Form-36; Musculoskeletal Function Assessment injury and arthritis survey) had been assessed for accuracy in five studies. The sensitivity, specificity, reliability or validity, of these tests remains unclear for this patient population. Further work is needed to assess the appropriateness of the identified tests and outcomes for patellar instability cohorts.

Metric measurements and attachment levels of the medial patellofemoral ligament: an anatomical study in cadavers

OBJECTIVE

To determine the metric measurements and to verify the attachment levels of the medial patellofemoral ligament in human cadavers.

METHODS

Seventeen knees (eight right and nine left knees) from 10 cadavers (nine male and one female) were dissected and stored in a 10% formaldehyde solution. All of the knees were whole and did not show any macroscopic signs of injuries.

RESULTS

The medial patellofemoral ligament was present in 88% of the knees studied, localized transversally between the medial femoral epicondyle and the medial margin of the patella. Its dimensions were quite variable, even between the knees of the same individual. The width of the patellar insertion ranged from 16 to 38.8 mm, with a mean of 27.90 mm, and its mean length was 55.67 mm. The margins of the ligament were concave or rectilinear. At the upper margin, the concave form predominated and was better characterized, while at the lower margin, the rectilinear form predominated.

CONCLUSIONS

The medial patellofemoral ligament is a very distinct structure with variable anatomical aspects and is always located in a plane inferior to the vastus medialis obliquus muscle.

Comparison of isometric and anatomic reconstruction of the medial patellofemoral ligament: a cadaveric study

Recent surgical procedures designed to correct recurrent posttraumatic lateral patellar instability focus on reconstructing the medial patellofemoral ligament. This study evaluated and compared patellofemoral kinematics of isometric and anatomic medial patellofemoral ligament reconstructions. Using an infrared motion capture analysis system, patellar tracking was evaluated in the coronal plane in 6 cadaveric specimens. Reconstruction of the medial patellofemoral ligament using an isometric technique did not restore normal patellar tracking at any flexion angle; however, reconstruction using an anatomic technique restored statistically normal patellar tracking from maximal knee extension to 28 degrees of flexion. Neither technique was able to restore normal kinematics in deeper angles of knee flexion.

Current concepts review: comprehensive physical examination for instability of the knee

A careful history and physical examination are the cornerstones of orthopaedic sports medicine. When evaluating a patient for ligamentous instability of the knee joint, an understanding of the contribution of anatomic structures to stability enhances a practitioner's ability to achieve an accurate clinical diagnosis. This article reviews the various types of knee instability and the associated anatomic structures. Ultimately, information must be obtained from multiple tests to reach the final diagnosis. We describe in detail the pathologic and biomechanical basis of the tests for both tibiofemoral and patellofemoral instability of the knee joint and provide recommendations for performance and interpretation of these physical examinations.

The association between patella alignment and knee pain and function: an MRI study in persons with symptomatic knee osteoarthritis

OBJECTIVE

The aim of the study was to examine the association between patellofemoral (PF) alignment (using standard magnetic resonance imaging (MRI) images of extended knees) and knee pain and function.

DESIGN

Subjects were recruited to participate in a natural history study of symptomatic knee osteoarthritis, called the Boston Osteoarthritis of the Knee Study (BOKS). The association of predictive variable (patellar alignment in sagittal and transverse planes) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function were examined using a linear regression model while adjusting for age, sex, body mass index (BMI), Center for Epidemiologic Studies Depression Scale (CES-D) score and Kellgren and Lawrence score.

RESULTS

Increasing trochlear angle (TA) was associated with both WOMAC (P=0.06) pain and WOMAC function subscale (P=0.04). Increasing lateral patellar title angle (LPTA) and decreasing bisect offset (increasing lateral subluxation) appeared to be associated with increasing WOMAC pain. However, no such an association was observed for other predictors.

CONCLUSIONS

The findings of the present study suggest that increasing TA is associated with increased functional impairment. Other measures of PF malalignment were not significantly associated with either knee pain or functional impairment.

Arthroscopic findings at the time of patellar realignment surgery in adolescents

Articular cartilage injuries and loose bodies have been associated with patellar dislocations. At the time of patellar realignment surgery (PRS), direct intraarticular visualization of the structures of concern may be limited with the use of a small arthrotomy. Concomitant diagnostic arthroscopy can improve the identification of intraarticular abnormalities, both patellofemoral and nonpatellofemoral, because of the better field of view.

PURPOSE

This report details the findings from knee arthroscopy performed concomitantly with PRS in adolescents.

METHODS

All patients underwent knee arthroscopy and open PRS for patellar instability, performed by a single surgeon, during a 4-year period. Patient demographics, knee history, clinical examination, operative findings, and treatment details were collected on all patients.

RESULTS

: Thirty-eight patients (mean age, 14.9 years; 41 knees) were included in this analysis. Patellar osteochondral lesions were present in 30 knees (73%; mean size, 112 mm). Femoral lesions were documented in 11 knees (23%; mean size, 81 mm). Loose bodies were present in 6 knees (15%). In 8 patients (20%), an additional 11 nonpatellofemoral diagnoses were made at the time of arthroscopy: lateral tibiofemoral chondroses (n = 4), medial meniscal tear (n = 2), lateral meniscal tear (n = 2), discoid lateral meniscus (n = 1), partial anterior cruciate ligament tear (n = 1), and medial tibiofemoral chondrosis (n = 1). Because of these findings, 5 additional procedures were performed in 4 patients: partial lateral meniscectomy (n = 2), medial meniscal repair (n = 1), discoid meniscus saucerization (n = 1), and staged distal femoral valgus-correcting osteotomy (n = 1).

CONCLUSIONS

By performing concomitant knee arthroscopy at the time of PRS, we were able to identify significant tibiofemoral abnormality in 4 patients, which would have been missed with direct inspection by a limited arthrotomy at the patellofemoral joint. In addition, precise evaluation of the patellofemoral joint permits customization of the PRS and aids in establishing appropriate patient expectations postoperatively. We advocate diagnostic knee arthroscopy at the time of PRS in adolescents to identify all intraarticular abnormalities and to optimize discussions with the patient and the caregivers on the long-term prognosis of the knee.

SIGNIFICANCE

Arthroscopic inspection of the knee at the time of PRS permits identification of abnormality that is not routinely visual by using open arthrotomy. Twenty percent of patients had additional pathological findings; of these patients, 50% underwent an additional surgical procedure.

Tailored tibial tubercle transfer for patellofemoral malalignment: analysis of clinical outcomes

The purpose of this study was to describe the surgical technique, and evaluate and analyze the clinical outcomes of patients who underwent tibial tubercle realignment in our institution. Reported results of tibial tubercle transfer for patellofemoral malalignment vary considerably. Most authors rely mainly on the passive intraoperative patellar tracking test in determining the new location of the tibial tubercle. Conversely, the senior author relocates the tibial tubercle based on the intraoperative active and passive patellar tracking tests and the condition of the patellar articular surface. The medical records of 66 consecutive patients who underwent 80 tibial tubercle relocation procedures due to patellar instability or patellofemoral pain and maltracking were reviewed. Fifty-five patients with 69 operated knees participated in designated follow-ups which were conducted according to a predesigned protocol. The median follow-up was 6.2 years (range 2-13 years). Clinical outcomes significantly improved compared to the preoperative state; 72.5% of operated knees demonstrated good-to-excellent results according to the Lysholm and Karlsson scores, and physical findings supported the positive effect of the procedure. A statistically significant positive correlation was found between clinical outcomes and male gender, the absence of moderate to severe patellar chondral damage, and instability as the dominant preoperative symptom. Postoperative complication rate was low and patients with longer postoperative follow-ups demonstrated better clinical outcomes. The presented method of tibial tubercle transfer provided a good long-lasting surgical solution for patients with patellar instability and patients with patellar maltracking and anterior knee pain. Good prognostic factors included male gender, clinical patellar instability as the dominant preoperative symptom and intact patellar articular cartilage.

The measurement of patellar alignment in patellofemoral pain syndrome: are we confusing assumptions with evidence?

Patellofemoral pain syndrome is one of the most common orthopaedic complaints presenting to physical therapists. Although its etiology is uncertain, the cause is most often considered to be malalignment or lateral tracking of the patella. Consequently, measurement of patellar alignment has come to be accepted as an integral part of the examination of patellofemoral pain syndrome. Various measurement techniques exist, both clinical and radiological, and these have been frequently used in the diagnosis and treatment of the condition. As a corollary, the widespread use of such measurements has also lent weight to the theory that patellar malalignment is one of the primary causes of patellofemorai pain syndrome. However, an analysis of the literature reveals that the vast majority of these measurement procedures lack the appropriate scientific qualities to be considered acceptable measurement tools, including questionable reliability and validity, and an absence of appropriate normative data and a gold standard. This paper assesses the evidence for the usefulness of the most commonly used measures of patellar alignment and concludes that many of the beliefs of the clinical community with regard to the existence and measurement of patellar malalignment in patellofemoral pain syndrome may be based largely on assumptions and not on evidence.

Patellar tendon length after anterior cruciate ligament reconstruction: a comparative magnetic resonance imaging study between patellar and hamstring tendon autografts

Patellar tendon shortening after anterior cruciate ligament reconstruction may be associated with anterior knee pain or patellofemoral arthritis. The present study was designed to compare postoperative changes in patellar tendon length after anterior cruciate ligament reconstruction between patellar tendon and hamstring tendon autograft. Magnetic resonance images of both knees (operated and healthy) and functional outcome were documented at least 1 year postoperatively in 16 patellar tendon harvested patients and in 32 hamstrings harvested patients. Patellar tendon length, patella length and Insall-Salvati ratio were measured. The operated knee values were compared to the respective values of the non-operated control knees. A significant 4.2 mm or 9.7% patellar tendon shortening in patellar tendon group and a non-significant 1.14 mm or 2.6% shortening in hamstrings group was detected. No significant difference was detected in terms of major shortening-patella baja-(6% for the patellar tendon group vs. 0% for the hamstring group). There was no significant difference in anterior knee problems between the two groups as evidenced by the Shelbourne score (94 for the patellar tendon group vs. 98 for the hamstring group). Harvesting of the patellar tendon for anterior cruciate ligament reconstruction resulted in a significant shortening of the remaining tendon. In contrast harvesting of the hamstring tendons did not affect significantly the patellar tendon length. However, the incidence of patella baja and overall functional outcome was not significantly different between the two groups.

Medial patellofemoral ligament reconstruction: a new technique

Background

Primary patellofemoral dislocations are common. In most patients, non-operative management produces satisfactory outcome. If the dislocation recurs after a trial of rehabilitation, operative intervention is considered, with the aim of restoring the soft tissue anatomy to normal. Ninety four percent of patients suffer a tear to the medial patellofemoral ligament (MPFL) following a patellar dislocation.

Results

We describe our transverse patella double tunnel technique to reconstruct the medial patellofemoral ligament using a free autologous gracilis or semitendinous graft.

Medial patellofemoral ligament reconstruction: a novel technique using the patellar ligament

In patients with chronic patellofemoral instability, more than 2 episodes of dislocation, and an anterior tuberosity trochlear groove of less than 20 mm as measured on computed tomography or nuclear magnetic resonance imaging, we have developed a technique for medial patellofemoral ligament reconstruction that uses a medial strip of the patellar ligament (PL). The incision started proximally at the level of the superior margin of the patella, centrally between the patellar medial margin and the medial epicondyle. A descending incision was then made, directed toward the superomedial margin of the tibial tubercle. We performed a plane-by-plane dissection up to the peritenon of the PL. With an osteotome, we could remove a 2-cm bone fragment concerning the medial third of the distal insertion of the PL or keep the distal end free. Using a No. 11 scalpel blade, we carefully detached the PL from the patella up to the transition between the proximal third and medial third of the patella. We placed the stitches between the periosteum and the ligament using FiberWire absorbable threads (Arthrex, Naples, FL) to safely rotate the graft. After that, we dissected the medial capsule and approached the femoral medial epicondyle. Then we placed a Krackow suture in the free tendon end using absorbable threads or anchored the threads into 2 holes that were previously drilled, and we secured the end with an absorbable interference screw or anchors. The fixation should be performed with the knee at 15 degrees to 30 degrees of flexion. Then we sutured the distal edge of the vastus medialis muscle to the graft, which bestows a dynamic component upon the reconstruction, and we immobilized the knee with a removable brace.

High-resolution MRI using a microscopy coil for the diagnosis of recurrent lateral patellar dislocation

PURPOSE

Magnetic resonance imaging (MRI) has been commonly used for the preoperative evaluation of recurrent lateral patellar dislocation (RLPD). The purpose of this study was to determine the usefulness of high-resolution MRI (HR-MRI) with a microscopy coil for diagnosing RLPD.

MATERIALS AND METHODS

The study group consisted of 15 patients with clinically diagnosed RLPD and 10 normal volunteers. All studies were performed on a 1.5-T MR system. First, conventional MRIs of the whole knee joint were obtained using the knee coil. Then HR-MRI scans using a microscopy coil in the medial aspect of the patella were obtained at the level of the superior pole of the patella, targeting the medial patellofemoral ligament (MPFL). The acquired HR-MRIs with RLPD were reviewed concerning the MPFL injury and the patellar injury.

RESULTS

The MPFL was distinguished as a separate ligament, and the layer structure of the patellar cartilage was visualized clearly in all volunteers. The MPFL injury was visualized in 12 cases (87%); it included discontinuity, thickening, and loosening. The patellar injury was visualized in 11 cases (73%), which included dissecans of the medial margin and cartilage injuries.

CONCLUSION

HR-MRI with a microscopy coil provides precise information of the MPFL and patellar cartilage injury for the diagnosis of RLPD.

The effects of medialization and anteromedialization of the tibial tubercle on patellofemoral mechanics and kinematics

BACKGROUND

Medialization and anteromedialization of the tibial tubercle are used to correct patellar subluxation in adults.

PURPOSE

To compare the effects of the 2 osteotomies on patellofemoral joint contact pressures and kinematics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tibial tubercle osteotomies were performed on 10 cadaveric human knees. The knees were tested between 0 degrees and 90 degrees of flexion while dynamic patellofemoral joint contact pressure and kinematic data were simultaneously obtained. Four conditions were tested: normal knee alignment, simulated increased Q angle, postmedialization of the tibial tubercle, and postanteromedialization of the tubercle.

RESULTS

An increased Q angle laterally translated the patella, shifted force to the lateral facet, and increased patella contact pressures. Both medialization and anteromedialization partially corrected the abnormal contact pressures. Medialization partially corrected the shift of force to the lateral facet induced by an increased Q angle, whereas the anteromedialization could not. Both medialization and anteromedialization corrected the patella maltracking.

CONCLUSION

Medialization and anteromedialization are equivalent in their ability to correct abnormal patellar mechanics and kinematics.

Physical Examination and Patellofemoral Pain Syndrome

Patellofemoral pain syndrome, which accounts for 25% of all sports-related knee injuries, is multifactorial in origin. A combination of variables, including abnormal lower limb biomechanics, soft-tissue tightness, muscle weakness, and excessive exercise, may result in increased cartilage and subchondral bone stress, patellofemoral pain, and subtle or more overt patellar maltracking. Because of the multiple forces affecting the patellofemoral joint, the clinical evaluation and treatment of this disorder is challenging. An extensive search of the literature revealed no single gold-standard test maneuver for that disorder, and the reliability of the maneuvers described was generally low or untested. An abnormal Q-angle, generalized ligamentous laxity, hypomobile or hypermobile tenderness of the lateral patellar retinaculum, patellar tilt or mediolateral displacement, decreased flexibility of the iliotibial band and quadriceps, and quadriceps, hip abductor, and external rotator weakness were most often correlated with patellofemoral pain syndrome.

Estudo prospectivo e comparativo entre o tratamento conservador e o cirúrgico (reparo do ligamento femoropatelar medial) nas luxações agudas de patela

Foram avaliados dois grupos de pacientes com o primeiro episódio de luxação aguda femoropatelar traumática e acompanhados prospectivamente em relação às recidivas e aos fatores predisponentes à luxação. No Grupo I, 17 pacientes com média de idade de 24,6 anos, sendo 11 do sexo feminino, foram submetidos ao reparo do ligamento femoropatelar medial com menos de um mês de trauma. O tempo médio de seguimento foi de 40,4 meses e o mínimo de 18 meses. Como resultados, não houve nenhuma recidiva da luxação,houve dois episódios de subluxação . Nove pacientes apresentavam fatores predisponentes à luxação. No Grupo II, 15 pacientes com média de idade de 26,8 anos, sendo oito do sexo feminino, foram submetidos ao tratamento conservador com média de 18,5 dias de imobilização. O tempo de seguimento médio foi de 35,7 meses e o mínimo de 11 meses. Oito joelhos tiveram recidiva da luxação, apenas dois joelhos foram considerados estáveis . Neste grupo, 14 pacientes apresentavam fatores predisponentes. Concluímos que o tratamento cirúrgico das luxações agudas femoropatelares traumáticas apresenta resultados superiores quanto à recidiva em relação ao tratamento conservador no período estudado. A presença de fatores predisponentes em nossa série de pacientes não influenciou as recidivas das luxações femoropatelares.

Physical examination of the knee

Even with the rapid advancement in technology and medical imaging, there is still no substitute for the history and physical examination that can be obtained from a patient. With a well-performed history and physical, the majority of pathology can be determined prior to any expensive imaging or surgical procedures. The knee is one of the most commonly injured joints, and its function is critical to basic ambulation and participation in sports, work, and activities of daily living. This article reviews the key concepts to a complete evaluation of the knee and highlights aspects of the physical examination and radiographic imaging that best aid in diagnosing knee pathology.

Imaging of postoperative knee extensor mechanism

Disorders of the anterior knee are common and include patellofemoral syndrome, patella instability, patella fracture, and patellar and quadriceps tendon ruptures. Depending on the operative procedure performed, the post-operative imaging appearance of these knees may be confusing. It is crucial for the radiologist to be familiar with the procedures performed in order to recognize the postoperative findings. Radiologists must be able to interpret hardware (anchors, screw and wires) and disruptions in soft tissue planes that may persist with these types of procedures.

Tratamento da luxação femoro-patelar aguda pelo reparo do ligamento femoro-patelar medial

Os autores avaliaram a evolução de 17 pacientes que tiveram luxação femoropatelar aguda e foram tratados pela sutura do ligamento femoropatelar medial. A sutura do ligamento foi feita por via artroscópica em 9 pacientes que apresentaram a lesão do ligamento próxima à patela. Nos oito pacientes restantes a lesão do ligamento femoropatelar ocorreu próxima ao epicôndilo femoral e foi tratada pela reinserção no epicôndilo femoral com âncoras. Os pacientes foram acompanhados por um tempo médio de 40 meses e não houve nenhuma recidiva da luxação femoropatelar durante este período.

The anatomy and isometry of the medial patellofemoral ligament: implications for reconstruction

BACKGROUND

Several techniques have been described for reconstruction of the medial patellofemoral ligament. However, the isometry of the medial patellofemoral ligament has not been studied.

PURPOSE

To define the anatomy and isometry of the medial patellofemoral ligament.

STUDY TYPE

Cadaveric study.

METHODS

The authors dissected the medial patellofemoral ligament in 11 cadaveric knees and recorded its anatomic relationships. They evaluated the isometry of the medial patellofemoral ligament by obtaining measurements between various anatomic pairings at certain fixed angles of knee flexion.

RESULTS

During knee flexion from 0 degrees to 90 degrees, the portion of the medial patellofemoral ligament from the inferior patellar attachment to the superior femoral attachment was nearly isometric, demonstrating an average change in length of only 1.1 mm. Statistical analysis showed the superior femoral attachment to be most significant in determining isometric behavior.

CONCLUSIONS

The most isometric portion of the medial patellofemoral ligament is the inferior portion of its patellar attachment extending to the superior portion of its femoral attachment, with the superior femoral attachment having the most notable influences on isometry.

CLINICAL RELEVANCE

This study provides a detailed description of the anatomy of the medial patellofemoral ligament, as well as an evaluation of the isometric behavior of the ligament. Application of these data during reconstruction of the medial patellofemoral ligament may help to optimize patellofemoral stability.

Reducing the lateral force acting on the patella does not consistently decrease patellofemoral pressures

BACKGROUND

Extensor mechanism procedures that decrease the lateral component of the patellar tendon or quadriceps force acting on the patella do not consistently reduce pain.

HYPOTHESIS

Patellofemoral treatments do not consistently decrease patellofemoral pressures because of variations in the moments acting on the patella.

STUDY DESIGN

Computer simulation study.

METHODS

Computational models of 4 knees were constructed to characterize the patellofemoral pressure distribution during simulated squatting from 40 degrees to 90 degrees. The knees were given an initial Q angle of 25 degrees. Patellofemoral treatments were simulated by increasing the percentage of the quadriceps force applied by the vastus medialis by 50% and by medializing the tibial tuberosity to decrease the Q angle to 15 degrees.

RESULTS

Decreasing the Q angle caused a larger decrease in the lateral component of the force applied by the quadriceps and patellar tendon than did increasing the force applied by the vastus medialis and, therefore, was more effective at decreasing patellofemoral pressures and the force needed to resist lateral subluxation. Both treatments also decreased the moments acting to rotate the distal patella laterally and tilt the patella laterally during flexion. Variations in these moments increased patellofemoral pressures for some knees.

CONCLUSIONS

Treatments that reduce patellofemoral subluxation can have an unexpected influence on patellofemoral pressures because of the moments acting on the patella.

CLINICAL RELEVANCE

Extensor mechanism procedures that restore patellofemoral stability may not provide pain relief.

Traumatic patellar dislocation in children and adolescents: treatment update and literature review

PURPOSE OF REVIEW

Traumatic patellar dislocation in children and adolescents is a complex problem resulting from a range of anatomic and mechanical conditions. A careful review of the literature demonstrates certain risk factors that predispose children to recurrent dislocation. With this understanding, these conditions can be managed more aggressively in the hope of an improved outcome. Additionally, a vast number of surgical procedures to correct patellar instability have been described, and recent cadaveric studies are now guiding surgical interventions.

RECENT FINDINGS

Risk factors for recurrent dislocation may include various skeletal abnormalities, increased quadriceps angle, generalized ligamentous laxity, and family history. Recent anatomic and biomechanical studies have demonstrated that the medial patellofemoral ligament and the vastus medialis obliquus are the primary restraints to lateral translation and ultimately dislocation of the patella. Management should therefore be directed both at correcting anatomic abnormalities when indicated and at reconstruction of medial restraints to patellar tracking.

SUMMARY

The recommendation for management of a traumatic patellar dislocation in a skeletally immature patient is initially conservative, emphasizing early motion and quadriceps strengthening. However, in patients for whom conservative management has failed or who are at particularly high risk for dislocation and require surgical intervention, repair or reconstruction of the medial patellofemoral ligament is the treatment of choice. Recent works have included investigation of less invasive techniques in children.

Patients with lateral tracking patella have better pain relief following CT-guided tuberosity transfer than patients with unstable patella

In patients with either lateral tracking patella or unstable patella the pathological lateral position of the tuberosity can be corrected by a medial transfer. This study compared the results of subtle CT-guided correction of the tuberosity for objective unstable patella (n=27) with the results for lateral tracking patella (potential instability) as described by Dejour (n=16). Follow-up was 37 months. CT revealed a pathological lateralization of the tibial tuberosity-trochlear groove greater than 15 mm in 41 knees. These patients underwent medialization of the tibial tuberosity up to 10-12 mm lateral from the trochlear groove, and 28 patients underwent a distalization to normalize the Caton index to 1.0-1.2. Results were evaluated using Cox' method. Patients with objective patellar instability were rated as 11% excellent, 52% good, 33% fair, and 4% poor. All patients became stable except one who had a 6 degrees valgus alignment. Although 96% had improved stability, 33% of the patients still had pain. The patients with lateral tracking patella (potential instability) were rated as 37.5% excellent, 44% good, and 19% fair. The lower proportion of pain relief in patients with unstable patella is likely the result of the cartilage damage experienced by these patients following multiple dislocations. Thus the patient with lateral tracking patella without patella dislocations must be differentiated from the one with unstable patella. Their prognosis in pain relief is better.

Current concepts of lateral patella dislocation

Surgical treatment of patellar dislocations, acute and chronic, has evolved significantly over the past decade with the advance of biomechanical knowledge of patellofemoral restraints and injury patterns identified by physical examination and improved imaging techniques. There continues to be no consensus on treatment parameters. Despite the presence of predisposing factors, such as dysplasia or generalized hyperlaxity, medial retinacular injury associated with primary (first-time) patellar dislocations represents a ligament injury, which may result in residual laxity of the injured structure. This residual laxity is defined objectively by an increase in passive lateral excursion of the patella. Repair or reconstructive procedures to restore this medial constraint is considered paramount in any procedure to stabilize the patella against subsequent dislocations. How best to accomplish this continues to be a matter of debate. The establishment of a medial check-rein by either repairing or reconstructing the MPFL is the procedure of choice for stabilizing a kneecap after first-time dislocation, largely because the literature to date does not provide clear guidelines about when more extensive surgery is indicated. Whether or not all first-time dislocators have improved outcome after surgical repair remains speculative, however. Improved outcome would involve both the elimination of recurrent instability episodes and continued satisfactory function of this patella in activities-of-daily-living and sporting activities. These outcomes have not been studied critically in operative versus nonoperative treatment of first-time patellar dislocation. For the first-time dislocator, most investigators would agree that an arthroscopy should be performed if intra-articular chondral damage is suspected. Nonoperative management of first-time patellar dislocations continues to be the preferred practice pattern in the United States. If surgical management is elected, because of individual characteristics of the injury pattern or the patient's lifestyle, it is important to inspect the MPFL along its length and repair any or all ligamentous disruptions. If the ligament is avulsed from the medial epicondyle, reattachment to bone is necessary to restore passive restraint to lateral patella motion. MRI may be useful in order to identify the location and degree of medial soft tissue injury preoperatively. The establishment of a medial check-rein by either repairing or reconstructing the MPFL is a necessary component of all surgical procedures performed to correct objective lateral instability of the patella. The addition of a LRR should be additive to this procedure only when it facilitates other procedures to recenter the patella or when objective lateral tilt by physical examination measurements is present. A practical approach to surgery after patellar dislocation is the minimal amount of surgery necessary to re-establish objective constraints of the patella. Correcting dysplastic factors, in particular tibial tubercle transfers and trochleoplasties, are best reserved if more minimal surgery has failed. This failure is defined as continued functional instability of the kneecap.

Diagnosis and treatment of patients with patellofemoral pain

The patient-athlete with patellofemoral pain requires precise physical examination based on a thorough history. The nature of injury and specific physical findings, including detailed examination of the retinacular structure around the patella, will most accurately pinpoint the specific source of anterior knee pain or instability. Radiographs should include a standard 30 degrees to 45 degrees axial view of the patellae and a precise lateral radiograph. Nonoperative treatment is effective in most patients. Prone quadriceps muscle stretches, balanced strengthening, proprioceptive training, hip external rotator strengthening, patellar taping, orthotic devices, and effective bracing will help most patients avoid surgery. When surgery becomes necessary, indications must be specific. Lateral release is appropriate for patella tilt (abnormal rotation). Painful scar or retinaculum, neuromas, and pathologic plicae may require resection. Proximal patellar realignment may be accomplished using arthroscopic or a combined arthroscopic/mini-open approach. Symptomatic articular lesions and more profound malalignments may require medial or anteromedial tibial tubercle transfer. Clinicians should be particularly alert for symptoms of medial subluxation in postoperative patients and should use the provocative medial subluxation test followed by lateral displacement patellar bracing to confirm a diagnosis of medial patellar subluxation. This problem may be corrected in most patients using a lateral patellar tenodesis. Current thinking emphasizes precise diagnosis, rehabilitation involving the entire kinetic chain, restoration of patella homeostasis, minimal surgical intervention, and precise indications for more definitive corrective surgery.

Alterations of the extensor apparatus after anterior cruciate ligament reconstruction using the medial third of the patellar tendon

PURPOSE

The objective of this study was the ultrasound evaluation of the donor defect of the patellar tendon (PT) and the radiologic evaluation of the patella after harvesting of the medial third as a bone-patella tendon-bone (BPTB) graft for anterior cruciate ligament (ACL) reconstruction.

TYPE OF STUDY

This was a cohort study.

METHODS

In 45 patients who had ACL reconstruction, the extensor apparatus of the donor side was studied using ultrasound cross-sections and radiographs (anteroposterior, lateral, and a tangential view of the patella) 3 to 70 months postoperatively. Patients were divided into two groups. The early postoperative group (3 to 30 months postoperative) consisted of 27 patients (group A) and the late postoperative group (31 to 70 months postoperative) consisted of 18 patients (group B). The healthy contralateral extensor apparatus was used as control.

RESULTS

In group A, the standard ultrasound cross-section area of the PT increased by 20.48%, whereas in group B, it decreased by 4.88%. In group A, the patellar height was decreased by 9.21% in the donor side compared with the control. In group B, the patellar height was decreased by 7.02%. In group A, the Merchant's congruence angle increased by 11.59 degrees, and for group B, this angle increased by 3.82 degrees. This finding indicated that, after the 30th postoperative month, lateral displacement of the patella was not statistically significant (P =.38). In addition, no significant differences were found in the lateral patellofemoral angle in either group.

CONCLUSIONS

Our study indicates that the tendon defect is always healed and the final tendon cross-section area is 95% of the contralateral after the 30th postoperative month. In addition, there was a nonsignificant slight lateral displacement of the patella. In contrast, other studies found shown that there is a slight medial displacement of the PT after using the central third as a BPTB graft.

Alterations in the patella after a high tibial or distal femoral osteotomy

Knee osteotomies realign the knee in an attempt to better distribute forces across the knee. The anatomic and physiologic function of the extensor mechanism, which includes the quadriceps tendon, patella, and patella ligament, may be altered during this procedure. An understanding of these changes is important especially when additional surgery becomes necessary, such as a conversion to a total knee arthroplasty. The current authors discuss patella mechanics and changes in the patella associated with osteotomies about the knee and the influence on normal patella biomechanics. Although patella changes are uncommon after a distal femoral osteotomy, poor total knee arthroplasty outcomes after a high tibial osteotomy attributable to patella alterations exist. Surgical technique during the primary high tibial osteotomy and the conversion to the total knee arthroplasty can reliably improve the final outcome. Rigid internal fixation with early knee mobilization after high tibial osteotomy reduces the incidence of patella baja and improves total knee arthroplasty outcome after a high tibial osteotomy, whereas while patella changes after a distal femoral osteotomy are minimal and largely ignored.