Occurrence of free nerve endings in the soft tissue of the knee joint. A histologic investigation

A cadaveric study of the innervation of the anterior compartment of the knee

PURPOSE

Anterior knee pain can significantly affect the quality of life of those living with it. One approach to addressing anterior knee pain involves the selective denervation of the patella to reduce afferent pain transmission, but there has been no consensus on the number, location, or origin of the nerves innervating the patella. In this study, we review existing literature on anterior knee innervation and present findings from our cadaveric dissection to provide a detailed description of the innervation of the anterior knee joint.

MATERIALS AND METHODS

Two independent authors reviewed the literature on anterior knee innervation from PubMed and Embase, and a sub-search was conducted on the relationship between the infrapatellar branch of the saphenous nerve (IPBSN) and the anterior knee compartment. Subsequently, two fresh-frozen cadavers were dissected to determine whether the saphenous nerve innervates the anterior knee compartment and to confirm, through tissue biopsies stained with laminin and beta-III-tubulin, whether previously described nerves innervate the patella.

RESULTS

A total of 463 and 304 entries on patellar innervation and saphenous nerve anatomy, respectively, were identified through PubMed and Embase. Descriptions of the nerves innervating the patella were found to be inconsistent and are summarized. No studies identified branches of the IPBSN directly innervating the patella or patellar tendon. On cadaveric dissection, we found that anterior knee innervation comprised the nerves within the distal vastus medialis and lateralis muscles, the medial and lateral retinacular nerves, and occasionally a branch of the IPBSN that innervated the inferomedial anterior knee skin.

CONCLUSIONS

This study is the first to provide histological confirmation of patellar innervation by the IPBSN. Our findings suggest that an approach based on a positive response to differential nerve blocks, followed by resection of the nerves implicated in that anterior compartment knee pain, may be more effective in treating persistent anterior knee pain than circumferential electroablation of the patella or routine resection of the IPBSN.

LEVEL OF EVIDENCE

Level III.

Comparison of the effectiveness of intra-infrapatellar fat pad and intra-articular glucocorticoid injection in knee osteoarthritis patients with Hoffa's synovitis: protocol for a multicentre randomised controlled trial

INTRODUCTION

The infrapatellar fat pad and synovium are the sites of immune cell infiltration and the origin of proinflammation. Studies have shown that Hoffa's synovitis may be a sign of early-stage osteoarthritis (OA). However, there have been no effective interventions specifically for Hoffa's synovitis.

METHODS AND ANALYSIS

We will conduct a multicentre, multi-blind (participant, physician, outcome assessor and data analyst blinded) randomised controlled trial to compare the effectiveness of an intra-infrapatellar fat glucocorticoid versus an intra-articular injection for Hoffa's synovitis in patients with knee OA. We will recruit 236 knee OA patients with Hoffa's synovitis at outpatient clinics in three centres. We will randomly allocate them to two groups in a 1:1 ratio. One group will receive ultrasound-guided injection of 40 mg (1 mL) triamcinolone acetonide into the infrapatellar fat pad; the other group will receive ultrasound-guided injection of 40 mg (1 mL) triamcinolone acetonide into the knee joint cavity. All patients will be followed up at 2, 4, 8, 12 and 24 weeks after the injection. Primary outcomes are (1) Hoffa's synovitis improvement rate, measured with the MRI Osteoarthritis Knee Score system (superiority outcome) at 24 weeks and (2) pain intensity, measured with the Western Ontario and McMasters University Osteoarthritis Index (WOMAC) at 2 weeks post-injection. Secondary outcomes include Hoffa's synovitis score at 2 weeks post-injection, pain intensity with the numerical rating scale, WOMAC questionnaire score improvements (function, joint stiffness and total score), improvement rates in effusion synovitis at 2 and 24 weeks, articular cartilage thickness changes at 2 and 24 weeks, Intermittent and Constant Osteoarthritis Pain score, quality of life measured with the EuroQol-5D, OARSI-OMERACT response indicators, co-interventions and side effects at 2, 4, 8, 12 and 24 weeks.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Medical Ethics Committee of the Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (2023-178). Written informed consent will be obtained from all patients prior to data collection. The findings of this research will be shared through presentations at academic conferences and publications in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2400080474.

Clinical and radiologic outcomes in patients with meniscal root tears

BACKGROUND

Meniscal root tears can lead to early knee osteoarthritis and pain. This study aimed (1) to compare clinical and radiological outcomes between patients who underwent arthroscopic meniscal root repair after meniscal root tears and those who received non-surgical treatment, and (2) to identify whether baseline MRI findings could be potential predictors for future treatment strategies.

METHODS

Patients with meniscal root tears were identified from our picture archiving and communication system from 2016 to 2020. Two radiologists reviewed radiographs and MRI studies using Kellgren-Lawrence (KL) grading and a modified Whole Organ MRI Scoring (WORMS) at baseline and follow-up. The median (interquartile range [IQR]) of follow-up radiographs and MRI studies were 134 (44-443) days and 502 (260-1176) days, respectively. MR images were assessed for root tear-related findings. Pain scores using visual analogue scale (VAS) and management strategies (non-surgical vs. arthroscopic root repair) were also collected. Chi-squared tests and independent t-tests were used to assess differences regarding clinical and imaging variables between treatment groups. Logistic regression analyses were performed to evaluate the associations between baseline MRI findings and each future treatment.

RESULTS

Ninety patients were included. VAS pain scores were significantly (p < 0.01) lower after arthroscopic repair compared to conservative treatment (1.27±0.38vs.4±0.52) at the last follow-up visit with median (IQR) of 325 (180-1391) days. Increased meniscal extrusion (mm) was associated with higher odds of receiving non-surgical treatment (OR = 1.65, 95%CI 1.02-2.69, p = 0.04). The odds of having arthroscopic repair increased by 19% for every 1 mm increase in the distance of the tear from the root attachment (OR = 1.19, 95% CI: 1.05-1.36, p < 0.01). The odds of undergoing arthroscopic repair were reduced by 49% for every 1 mm increase in the extent of meniscal extrusion (OR = 0.51, 95% CI: 0.29-0.91, p = 0.02) as observed in the baseline MRI.

CONCLUSIONS

Patients who underwent arthroscopic repair had lower pain scores than patients with conservative treatment in the follow-up. Distance of the torn meniscus to the root attachment and the extent of meniscal extrusion were significant predictors for arthroscopic repair in the next three weeks (time from the baseline MRI to the surgery date).

Surgeon-placed peripheral nerve block and continuous non-opioid analgesia in total knee arthroplasty is accessible intraoperatively: A cadaveric study

BACKGROUND

Pain management in TKA patients is challenged by a postoperative requirement for early ambulation along with the concurrent goal of reducing opioid consumption while simultaneously reducing the length of hospital stay. Peripheral nerve blocks (PNB) address these concerns to some degree, with femoral nerve and adductor canal blocks being the most-used regional nerve blocks for surgeries performed around the knee joint.

PURPOSE

The authors hypothesized that placing a catheter between the muscles that make up the adductor canal during a standard surgical approach for a Total Knee Arthroplasty would provide equitable or superior access for a peripheral nerve block in the adductor canal. The nerves that are located between the muscles that make up the adductor canal transmit the majority of the pain after TKA.

METHODS

This cadaveric study was conducted in 12 fresh-frozen human cadaveric lower limbs, comparing the standard technique of adductor canal block, placed under ultrasound guidance, to this experimental technique. Using colored indicator dyes to locate the site of surrogate peripheral nerves, the techniques were compared.

RESULTS

Through a standard anterior surgical approach to the knee, an intraoperative catheter placement technique can be performed to provide a peripheral nerve block to the saphenous nerve for patients undergoing TKA that is comparable to standard ultrasound guided anesthesia block techniques.

CONCLUSIONS

This cadaveric study demonstrates the availability for the surgeon to place a catheter between the muscles that form the adductor canal during a standard surgical approach for TKA. This novel technique can provide equivalent coverage of the nerves for an ACB when compared to a standard ultrasound guided ACB.

Periarticular Injection in Total Knee Arthroplasty

Optimal pain management after total knee arthroplasty (TKA) can expedite postoperative recovery, improve perioperative outcomes, and increase patient satisfaction. Periarticular injections (PAIs) have become increasingly used to improve pain management after TKA. Similar to peripheral nerve blocks, the use of intraoperative PAIs can lower pain scores and expedite discharge from the hospital. However, there is notable variability in the ingredients and administration techniques of PAIs. Currently, no standard of care exists for PAIs, especially in the setting of adjuvant peripheral nerve blocks. This study seeks to evaluate the ingredients, administration techniques, and outcomes of PAIs used during TKA.

Load-deformation characteristics of cadaver patellae: Relationship to intraosseous pressure

BACKGROUND

Anterior knee pain can arise from several sources. One of the main sources of pain in patients with anterior knee pain is the patella. Increased patellofemoral joint loading is the prime source of patellar pain. Elevated intraosseous pressures have been measured in painful patellae and increasing the intraosseous fluid pressure in the patella causes pain. Whether elevated fluid pressure is an independent source of pain or if the patellar deformation under load leads to elevated pressure and pain has not been determined. Our hypothesis was that the patella deforms measurably under physiologic loads and that intraosseous pressure increase is related to that deformation. The relationship may be linear as measured by correlation or nonlinear as measured by the sum of squared error.

METHODS

Part I: Assessment of patellar load-deformation profiles were obtained in 2 intact cadaver patellae and 1 bisected patella under physiologic loads. Part II: Measurements of intraosseous pressure were obtained in 9 cadaver patellae as the patellae were compressed with physiologic loads. Pressures were recorded at sequential levels of anterior-posterior patellar compression.

FINDINGS

Cadaver patellae compress up to 3.5 mm in the anterior-posterior plane. Compression with physiologic forces raises intraosseous pressure to more than 40 mmHg.

INTERPRETATION

Load-deformation of cadaver patellae results in deformation and an increase in intraosseous pressure. These findings may help explain previous studies of patellofemoral pain where elevated patellar intraosseous pressures have been found in vivo.

Are Patellofemoral Ligaments and Retinacula Distinct Structures of the Knee Joint? An Anatomic, Histological and Magnetic Resonance Imaging Study

There is disagreement regarding the description of the patellofemoral ligaments (PFLs), considered by some authors as capsular thickening and by others as independent ligaments. It was hypothesised that the PFLs and retinacula are structures with different histological features. The aim of this study was to describe the stabilising structures of the patella in detail and to determine if the PFLs and retinacula are different and separable structures from a macroscopic, microscopic and imaging viewpoint. An anatomical study was performed on eight knees from five cadavers (mean age, 56.2 years; range, 35–63 years), and a histological study was conducted on specimens from nine patients having a mean age of 65 years (range 35–84 years) who had undergone surgical knee procedures. The imaging study was based on 100 MRIs (96 patients). The mean age was 46 years (range 16–88), and the study analysed the capsular-ligamentous structures. In the medial compartment, the layers and structures were as follows: superficial layer, medial retinaculum; intermediate layer, Medial Collateral Ligament (MCL), Posterior Oblique Ligament (POL) and Medial Patellofemoral Ligament (MPFL); deep layer, deep part of the MCL and joint capsule. In the lateral compartment, the layers and structures were the following: superficial layer, lateral retinaculum; intermediate layer, Lateral Collateral Ligament (LCL) and Lateral Patellofemoral Ligament (LPFL); deep layer, joint capsule. All of the knees examined presented a clearly distinguishable MPFL and LPFL separable from the capsular layer. Histological study: there was a higher density of nerve fibres in retinacula compared to ligaments (p = 0.0034) and a higher content of elastic fibres in retinacula (p < 0.0005). In imaging, there was no difference between medial and lateral retinaculum thickness (p > 0.05). In conclusion, both the lateral and medial compartment can be described using the three-layer scheme. PFLs and retinacula are separate structures both macroscopically and according to imaging analysis. The retinacula respond to their specific function with a higher nerve fibre content and higher number of elastic fibres compared to the ligaments.

Clinical Anatomy of the Anterior Meniscofemoral Ligament of Humphrey: An Original MRI Study, Meta-analysis, and Systematic Review

Background:

The anterior meniscofemoral ligament (aMFL) of Humphrey is an anatomically variable fibrous band of connective tissue that attaches between the lateral aspect of the medial femoral condyle and posterior horn of the lateral meniscus, running posterior to the anterior cruciate ligament and anterior to the posterior cruciate ligament (PCL). The presence of an intact aMFL may contribute to stabilization of the lateral compartment of the knee joint.

Purpose:

The original magnetic resonance imaging (MRI) arm of this study aimed to assess the aMFL incidence among Polish patients. The goal of the systematic review and meta-analysis was to review the literature discussing the clinical anatomy of the aMFL and provide data on its prevalence. It was hypothesized that significant heterogeneity exists within the published literature.

Study Design:

Cross-sectional study and systematic review; Level of evidence, 3.

Methods:

A retrospective investigation was performed on the MRI scans of 100 knees (52 right, 48 left) of Polish patients. Scans were randomly selected from a database of MRI examinations performed in 2019. For the meta-analysis, major online databases were queried for data on the aMFL, and 2 authors independently assessed and extracted data from all included studies. A quality assessment of the included articles was performed using the Anatomical Quality Assessment tool.

Results:

In the MRI arm of this study, the aMFL was found in 62 of the 100 lower limbs. The meta-analysis included 41 studies with a total of 4220 limbs. The aMFL was present in 55.5% (95% CI, 45.5%-65.3%) of cases. Arthroscopic studies yielded the highest prevalence (82.3% [95% CI, 36.6%-100.0%]); of MRI studies, the highest prevalence was at 3.0-T strength (51.0% [95% CI, 13.3%-88.2%]).

Conclusion:

Significant variability in the prevalence of the aMFL was found in the literature. More emphasis should be placed on the clinical relevance of injuries to the aMFL because of its significant role in the function of the knee. It is important to be aware that, because of the anatomy of the aMFL, the ligament can also function to support a torn PCL.

Hip preservation surgery and the acetabular fossa

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Anterior knee pain in ACL reconstruction with BPTB graft - Is it a myth? Comparative outcome analysis with hamstring graft in 1,250 patients

Anterior Knee Pain(AKP) has been quoted as the main disadvantage of Bone Patellar Tendon Bone (BPTB)graft in Anterior Cruciate Ligament Reconstruction (ACLR). We overcome the problem by harvesting BPTB graft by mini-open mobile window technique.

Objectives

To investigate postoperative incidence of AKP with BPTB graft in comparison with hamstring graft during primary ACLR.

Methods

Total of 1737 patients underwent ACLR in the study period of which 1250 met eligibility criteria (622-BPTB graft, , 628-Hamstring graft).

Results

Incidence of AKP, Lysholm score and IKDC score were analysed and found no statistically significant difference at 18-month followup.

Conclusion

BPTB graft harvested by mini-open mobile window technique has a low incidence of AKP as of hamstring graft.

Knee Ligament Anatomy and Biomechanics

An understanding of knee ligament anatomy and biomechanics is foundational for physicians treating knee injuries, especially the more rare and morbid multiligamentous knee injuries. This chapter examines the roles that the cruciate and collateral anatomy and morphology play in their kinematics. Additionally, the biomechanics of the ACL, PCL, MCL, and LCL are discussed as they have surgical and reconstructive implications.

Evidence-based Review of Periarticular Injections and Peripheral Nerve Blocks in Total Knee Arthroplasty

Background:

Recently, post-operative pain management after Total Knee Arthroplasty (TKA) has focused on a multimodal approach for reducing opioid requirements, promoting early rehabilitation, and expediting discharge from hospital. Regional anesthesia, in the form of Periarticular Injections (PAI) and Peripheral Nerve Blocks (PNB), has shown promise as adjunctive therapy to oral analgesics.

Objective:

To review the current literature surrounding regional anesthesia for TKA.

Discussion:

PNBs provide effective analgesia after TKA. Historically, femoral nerve blocks (FNB) have been commonly employed. FNBs, however, lead to the significant motor blockade to the quadriceps musculature, which can dampen early rehabilitation efforts and increase the risk of post-operative falls. Adductor Canal Blocks (ACB) have shown excellent results in reducing post-operative pain while minimizing motor blockade. Periarticular injections (PAI), and infiltration between the popliteal Artery and Capsule of the Knee (IPACK) have similarly helped in reducing patient discomfort after TKA and providing analgesia to the posterior capsular region of the knee.

Conclusion:

PAIs, and PNBs are important elements in many multimodal postoperative pain management protocols after TKA. Current evidence appears to suggest that a combination of an ACB supplemented by posterior capsular analgesic coverage through PAI or IPACK may provide optimal results.

The Efficacy of Liposomal Bupivacaine Over Traditional Local Anesthetics in Periarticular Infiltration and Regional Anesthesia During Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

Since its Food and Drug Administration approval in 2011 as a local anesthetic for postsurgical analgesia, liposomal bupivacaine (LB) has been incorporated into the periarticular injection (PAI) of many knee surgeons. The slow release of this medication from vesicles should significantly extend the duration of its analgesic effect, but current evidence has not clearly demonstrated this benefit.

METHODS

We systematically searched electronic databases including PubMed, MEDLINE, Cochrane Library, EMBASE, ScienceDirect, and Scopus, as well as the Journal of Arthroplasty web page for relevant articles. All calculations were made using Review Manager 5.3.

RESULTS

We identified 42 studies that compared LB to an alternate analgesic modality. Seventeen of these studies were controlled trials that were included in meta-analysis. Significant differences were seen in pain scores with LB over a peripheral nerve block (mean difference = 0.45, P = .02) and LB over a traditional PAI (standard mean difference = -0.08, P = .004).

CONCLUSION

While LB may offer a statistically significant benefit over a traditional PAI, the increase in pain control may not be clinically significant and it does not appear to offer a benefit in reducing opioid consumption. However, there is no standardization among current studies, as they vary greatly in design, infiltration technique, and outcome measurement, which precludes any reliable summarization of their results. Future independent studies using a standardized protocol are needed to provide clear unbiased evidence.

A comparative study comparing area of extension of posterior knee capsule via posteromedial injection: a cadaveric study

BACKGROUND

Periarticular multimodal drug injection (PMDI) has gained popularity as common postoperative pain protocols in knee arthroplasty. PMDI sites can vary, but posterior capsule (PC) is a common injection site because of its abundance of pain nociceptors.

PURPOSE

To prove the hypothesis whether posteromedial drug injection alone is sufficient to provide enough effect covering the PC in order to reduce risks of neurovascular injury. Secondary outcomes are to find proper volume of injection and safe zone for PMDI injection.

METHODS

Ten fresh cadaveric knees were allocated into two equal groups, which differed in volume of dye injection: 25 ml and 50 ml. Dyes were injected into posteromedial capsule compartment, and the limbs were stored in a freezer for 2 weeks. Then the posterior compartment was carefully dissected to examine spreading of the dye solution.

RESULTS

No dye staining was seen superficially beneath subcutaneous tissue of the knees. In deeper layer, the dye mostly occupied medially along the fascia covering semimembranosus muscles. However, dispersion was limited distally by intermuscular septa and popliteal vessels. The 50-ml injection group provided wider extension in the superficial layer, but not in the deep layer.

CONCLUSION

The intermuscular septa and the fascia of popliteal vessels were shown to be the boundary between posteromedial and posterolateral compartments of the knee. Separate PMDI for both compartments is necessary to occupy the entire PC. We suggest that 1.5 cm lateral to lateral border of PCL insertion, just above popliteus tendon, is the safe zone for injecting PMDI into the posterolateral capsule.

Importance of Mechanoreceptors and Other Neural Structures Within the Anterior Intermeniscal Ligament in the Etiology of Anterior Knee Pain After Tibial Nailing

BACKGROUND

Anterior knee pain is the most common complication after intramedullary tibial nailing. The cause is often multifactorial and varies among individuals. Violation of the anterior intermeniscal ligament (AIL) during intramedullary tibial nailing might be a possible source of postsurgical anterior knee pain. Although there is a certain ambiguity regarding the importance and function of the AIL, neural structures in the AIL tissue might play a significant role with respect to functional purposes and pain perception.

METHODS

We subjected 6 AIL specimens to histologic examination to identify the neural structures that are a mandatory requirement as a source of anterior knee pain. Specifically, we performed three-dimensional immunohistochemical investigation of subtyping, orientation, and detailed characterization of neural structures within the AIL tissue.

RESULTS

Histologic and three-dimensional immunohistochemical examinations confirmed the presence of neural structures in all 6 AIL specimens. We identified myelinated and unmyelinated nerve fibers, as well as all types of mechanoreceptors.

CONCLUSIONS

Free nerve endings are a mandatory requirement for pain perception as a result of AIL violation during tibial nailing. Our verification of all different types of mechanoreceptors in the AIL tissue makes a role of the ligament in knee joint function and proprioception highly probable. Further investigations are necessary to clarify possible correlations between neural supply and function of the AIL. Violation of the ligament during operative procedures should be avoided, although the significance of the AIL is still debated.

Anterior intermeniscal ligament: frequency in MRI studies and spatial relationship to the entry point for intramedullary tibial nailing related to the risk of iatrogenic violation

BACKGROUND

Anterior knee pain is the most common complication after intramedullary tibial nailing. Often, the cause is multifactorial and individually different. Violation of the anterior intermeniscal ligament (AIL) during intramedullary tibial nailing might be a possible origin of postsurgical anterior knee pain. Both the importance and function of the AIL remain somewhat ambivalent, and even the figures quoted in the literature for its existence in the population vary drastically. Our aim was to verify the estimated frequency of the AIL in the literature by retrospectively analysing the data of MRI studies conducted at our hospital. In addition, we attempted to assess the potential risk of AIL violation during intramedullary tibial nailing, based on the spatial arrangement.

METHODS

Two independent examiners analysed the images generated in 351 MRI studies conducted at our hospital between June 2013 and May 2014. All cases who did not reveal any previous knee-joint injury or osteoarthritis of the knee were allocated to group I. All other cases were included in group II. To estimate the potential risk of AIL injury during the nailing procedure, the distance between the AIL and the theoretical entry point for intramedullary nailing was measured.

RESULTS

We identified the AIL on the images of nearly all patients (96.5%) in group I. In group II, the presence of the AIL was confirmed in only 51.4% of cases (p < 0.001). The average distance between the AIL and theoretical entry point for intramedullary tibial nailing was 10.1 mm (range 3.48-18.88 mm).

CONCLUSIONS

Because we were able to confirm the presence of the AIL in nearly all patients without a history of knee joint injuries or osteoarthrosis, we presume that the AIL may play a role in knee joint function. Violation of the AIL during intramedullary nailing appears likely due to the close position of the AIL in relation to the entry point for the inserted nail. As a result and due to its rich sensory innervation, a connection between AIL violation during tibial nailing and postoperative onset of anterior knee pain seems likely. To eliminate one risk factor of anterior knee pain development and in view of the unresolved issues of AIL function, violation of the ligament during any operative procedure should be avoided.

3-Tesla MRI: Beneficial visualization of the meniscofemoral ligaments?

BACKGROUND

Recent investigations have confirmed an important stabilizing and protective function of the meniscofemoral ligaments (MFLs) to the knee joint and suggest a clinical relevance. Concerning their incidences, however, there have been discrepancies between data acquired from cadaveric studies and MRI data using 0.3- to 1.5-Tesla field strengths probably due to lower resolution. This study aims to investigate whether imaging with 3-Tesla magnetic resonance imaging (3-T MRI) is beneficial in gaining information regarding the ligaments' incidence, length, width and anatomic variation.

METHODS

3-T MRI images of 448 patients (224 males, 224 females, with, respectively, 32 patients of each sex in the age groups: 0-20, 21-30, 31-40, 41-50, 51-60, 61-70, >70years) were retrospectively reviewed. The influence of the parameters 'sex' and 'age' was determined.

RESULTS

Whereas 71% of the patients had at least one MFL, 22% had an anterior MFL (aMFL), 53% had a posterior MFL (pMFL) and five percent had coexisting ligaments. The pMFLs were more likely to be present in female patients (P<0.05) but if so, they were longer in the males (P<0.05). The pMFL was categorized according to its insertion on the medial femoral condyle.

CONCLUSIONS

3-T MRI enables an excellent illustration of the anatomic variations of pMFLs. By modifying an anatomic classification for radiological use we measured lengths and widths of the MFLs without any difficulties. Despite its increased resolution, 3-T MRI lends no diagnostic benefit in visualizing the course of the aMFL or filigree coexisting ligaments as compared to MRI at lower field strengths.

Lower numbers of mechanoreceptors in the posterior cruciate ligament and anterior capsule of the osteoarthritic knees

PURPOSE

Impaired proprioception accuracy of the knee has been proposed as a local factor in the onset and progression of knee osteoarthritis. Patients with decreased numbers of mechanoreceptors could be more likely to develop arthrosis due to a loss in proprioception of the joint. We aimed to identify and quantify the mechanoreceptors of the posterior cruciate ligament (PCL), the anterior capsule (AC) and the medial meniscocapsular junction (MCJ) in knee arthrosis.

METHODS

PCLs, ACs and MCJs were harvested from 30 patients with Kellgren and Lawrence grades 3 and 4 osteoarthritis (OA), and ten knees taken from five cadavers without OA were used as a control group. PCL degeneration was evaluated with haematoxylin & eosin, and the types and numbers of mechanoreceptors were evaluated using S100 immunostaining.

RESULTS

The patient ages in the OA and control groups (n.s.) did not differ. PCL degeneration was more severe in the gonarthrosis group than in the control group (p = 0.04). The numbers of Golgi corpuscles, Ruffini corpuscles, free nerve endings, total nerve endings and small vessels of the PCL were low in the OA group, as were the numbers of Golgi corpuscles, free nerve endings and total nerve endings of the AC. No significant correlation was found regarding the mechanoreceptors of the MCJ between the two groups.

CONCLUSION

The numbers of mechanoreceptors in patients with OA were low in the PCLs and ACs. A loss in proprioception could be a local risk factor in OA. The proprioceptive impact of preserving PCL while performing total knee arthroplasty may not be exaggerated as its thought.

LEVEL OF EVIDENCE

Prognostic study, Level I.

Periarticular Injections in Knee and Hip Arthroplasty: Where and What to Inject

BACKGROUND

Periarticular injections have become a valuable adjunct to multimodal pain control regimens after knee and hip arthroplasties. Injection techniques vary greatly among surgeons with little standardization of practice.

METHODS

We performed an extensive literature search to determine where nociceptive pain fibers are located in the hip and the knee and also to explore the pharmacology of periarticular cocktail ingredients.

RESULTS

Large concentrations of nociceptors are present throughout the various tissues of the knee joint with elevated concentrations in the infrapatellar fat pad, fibrous capsule, ligament insertions, periosteum, subchondral bone, and lateral retinaculum. Less empiric evidence is available on nociceptor locations in the hip joint, but they are known to be located diffusely throughout the hip capsule with elevated concentrations at the labral base and central ligamentum teres. Local anesthetics are the base ingredient in most injection cocktails and function by blocking voltage-gated sodium channels. Liposomal anesthetics may offer longer duration of action over traditional anesthetics. Nonsteroidal anti-inflammatory agents and corticosteroids block peripheral production of inflammatory mediators and may desensitize nociceptors. Opioid receptors are present in lower densities peripherally as compared with the central nervous system, but their inclusion in injections can lead to pain relief. Sympathetic drugs can provide adjunct effects to periarticular cocktails to increase duration of action and effectiveness of medications.

CONCLUSION

Targeting specific sites of nociceptors may help to further decrease pain after knee and hip arthroplasties. Altering periarticular cocktail ingredients may aid in multimodal pain control with injections.

Intra-osseous local anaesthetic patellar pain catheter suppresses osteoarthritic patello-femoral pain

BACKGROUND

The source of pain in patellofemoral osteoarthritis is not fully understood. The purpose of this study was to identify the origin of pain using intraosseous pain catheters and to show early results with an osteotomy that is potentially denervating and hydrostatic pressure-relieving.

METHODS

Five patients with patellofemoral osteoarthritis and pain with straight downward patellofemoral compression were included. All underwent arthroscopic placement of two 0.8mm catheters into the medial and lateral patella prior to subsequent patellar facetectomy with an incomplete horizontal patellar osteotomy. The catheters were first flushed with 0.5ml saline, then with local anaesthetic to determine pain response. After a mean of 44months the latest clinical examination was performed.

RESULTS

Instillation of less than 0.5ml of saline provoked sharp pain, which could be localised by all patients as medial or lateral within the patella. Subsequent instillation of local anaesthetic suppressed the mean patellar tenderness during axial compression from VAS 6 to VAS 1. In one of the five patients, patellar osteotomy did not relieve symptoms and further surgical intervention was required. The remaining four patients experienced a clinical improvement with a mean subjective knee value of 55 (range 40 to 65) out of 100.

CONCLUSION

This is the first report on intraosseous catheters applying local anaesthetics into bone. There is a surprisingly precise intraosseous spatial resolution of pain perception in the patella and triggering of pain in osteoarthritis appears at least in part to occur through intraosseous increase of hydrostatic pressure.

LEVEL OF EVIDENCE

Level IV, Case Series.

Permanent knee sensorimotor system changes following ACL injury and surgery

The cruciate ligaments are components of the knee capsuloligamentous system providing vital neurosensory and biomechanical function. Since most historical primary ACL repair attempts were unsuccessful, reconstruction has become the preferred surgery. However, an increased understanding of the efficacy of lesion-site scaffolding, innovative suturing methods and materials, and evolving use of biological healing mediators such as platelet-rich plasma and stem cells has prompted reconsideration of what was once believed to be impossible. A growing number of in vivo animal studies and prospective clinical studies are providing increasing support for this intervention. The significance of ACL repair rather than reconstruction is that it more likely preserves the native neurosensory system, entheses, and ACL footprints. Tissue preservation combined with restored biomechanical function increases the likelihood for premorbid neuromuscular control system and dynamic knee stability recovery. This recovery should increase the potential for more patients to safely return to sports at their desired intensity and frequency. This current concepts paper revisits cruciate ligament neurosensory and neurovascular anatomy from the perspective of knee capsuloligamentous system function. Peripheral and central nerve pathways and central cortical representation mapping are also discussed. Surgical restoration of a more physiologically sound knee joint may be essential to solving the osteoarthritis dilemma. Innovative rehabilitative strategies and outcome measurement methodologies using more holistic and clinically relevant measurements that closely link biomechanical and neurosensory characteristics of physiological ACL function are discussed. Greater consideration of task-specific patient physical function and psychobehavioral links should better delineate the true efficacy of all ACL surgical and non-surgical interventions. Level of evidence IV.

Running Injuries: The Infrapatellar Fat Pad and Plica Injuries

When considering knee pain in runners, clinicians differentiate sources of symptoms and determine their cause. Knee problems arise when a runner increases the amount/frequency of the loading through the lower limb. The way the loading is distributed through the knee determines which tissues are abnormally loaded. Knee problems cannot be considered in isolation, requiring a thorough investigation of static and dynamic lower limb mechanics, and footwear and surfaces. This article examines potential sources of knee pain and explores the role of the infrapatellar fat pad and synovial plica in the mechanics of the knee and its involvement in knee symptoms.

Mechanoreceptors of the ligaments and tendons around the knee

Proprioceptive inputs from the joints and limbs arise from mechanoreceptors in the muscles, ligaments and tendons. The knee joint has a wide range of movements, and proper neuroanatomical organization is critical for knee stability. Four ligaments (the anterior (ACL) and posterior (PCL) cruciate ligaments and the medial (MCL) and lateral (LCL) collateral ligaments) and four tendons (the semitendinosus (STT), gracilis (GT), popliteal (PoT), and patellar (PaT) tendons) from eight fresh frozen cadavers were harvested. Each harvested tissue was divided into its bone insertion side and its tendinous part for immunohistochemical examination using S100 staining. Freeman-Wyke's classification was used to identify the mechanoreceptors. The mechanoreceptors were usually located close to the bone insertion. Free nerve endings followed by Ruffini endings were the most common mechanoreceptors overall. No Pacini corpuscles were observed; free nerve endings and Golgi-like endings were most frequent in the PCL (PCL-PaT: P = 0.0.1, PCL-STT: P = 0.00), and Ruffini endings in the popliteal tendon (PoT-PaT: P = 0.00, Pot-STT: P = 0.00, PoT-LCL: P = 0.00, PoT-GT: P = 0.00, PoT-ACL: P = 0.09). The cruciate ligaments had more mechanoreceptors than the medial structures (MS) or the patellar tendon (CR-Pat: P = 0.000, CR-MS: P = 0.01). The differences in mechanoreceptor distributions between the ligaments and tendons could reflect the different roles of these structures in the dynamic coordination of knee motion. Clin. Anat. 29:789-795, 2016. © 2016 Wiley Periodicals, Inc.

NERVE ENDINGS AND VASCULAR SUPPLY IN SEMITENDINOSUS TENDON OF CEREBRAL PALSY CHILDREN

Objective: To evaluate the distribution of SP (substance P) and S-100 peptide immunoreactivity, as well as the vascular supply of tissues commonly used as grafts for anterior cruciate ligament (ACL) reconstruction. A second aim was to compare the above mentioned distribution in the semitendinosus muscle tendons of cerebral palsy (CP) patients with the semitendinosus muscle tendons and patellar tendons of patients without CP. Methods: The first group consisted of 14 children with cerebral palsy with a mean age of 11.7 years old. At the time of hamstring lengthening operation, a sample of semitendinosus muscle was taken for analysis. The second group comprised 20 patients treated for isolated ACL rupture of the knee (mean age 32 years old). Group three comprised ten patients in the mean age of 14.3 years old treated for recurrent lateral patellar dislocation, and from whom a sample of patellar tendon was obtained. Results: No statistically significant differences were demonstrated with regard to the amount of immunopositive nerve fibers expressing SP or S-100 in all 3 groups of patients. A significant difference was noted in the number of blood vessels between the adult and child semitendinosus muscles, but not between the semitendinosus muscles and patellar tendon of children. Conclusion: The number of nociceptors as well as proprioceptive fibers is similar in patients with CP and patients from a neurologically healthy population. Level of Evidence IV, Cases Series.

Periarticular regional analgesia in total knee arthroplasty: a review of the neuroanatomy and injection technique

Postoperative pain control after total knee arthroplasty may be insufficient, resulting in insomnia, antalgic ambulation, and difficulty with rehabilitation. Current strategies, including the use of femoral nerve catheters, may control pain but have been associated with falls, motor blockade, and quadriceps inhibition. Periarticular infiltration using the appropriate technique and knowledge of intraarticular knee anatomy may increase pain control and maximize rehabilitation.

Lateral patellar facetectomy and medial reefing in patients with lateral facet syndrome after patellar-retaining total knee arthroplasty

We analyzed clinical outcomes of partial lateral patellar facetectomy and medial reefing in patients with lateral patellar facet syndrome with painful patellar-retaining total knee arthroplasty. 34 patients were followed for a mean of 40 months. All 34 patients were matched with those having secondary patellar resurfacing without facetectomy. Both groups experienced significant pain relief and range of motion improvement. The facetectomy group had higher Kujala scores than those in patellar resurfacing group. Patients with facetectomy had significantly less pain postoperatively. There were significant differences in postoperative lateral patellar tilt and congruency angle in both groups. The mid-term results for LPF with medial reefing are promising to resolve pain in patients with lateral patellar facet syndrome in patellar-retaining TKA. Therapeutic level III (retrospective comparative study).

Temporary hemiepiphysiodesis of the distal medial femur: MPFL in danger

INTRODUCTION

Temporary hemiepiphysiodesis (TH) with plate fixation is a well-accepted and common treatment for correcting leg malalignment in skeletally immature patients. The purpose of this study was to investigate any soft tissue damage caused during TH at the distal medial femur with a plate and two screws. We hypothesized that correct plate placement can affect the integrity of the medial stabilizing structures of the knee, especially the medial patellofemoral ligament (MPFL), the medial collateral ligament (MCL) or result in arthrotomy of the knee joint itself.

MATERIALS AND METHODS

In eight cadaveric knees of five adult humans a TH was performed with a plate and two cancellous screws at the distal medial femur using a standardized surgical technique. Subsequently the medial capsular and ligamentous structures were systematically exposed and assessed. Capsular and synovial tissue was also inspected for impingement by the plate or screws.

RESULTS

In all knees the MPFL was present. In two specimens the MPFL was intact and the plate was lying over the dorsal part of the MPFL close to the MCL. The MPFL was completely cut in two cases in the central part of the ligament. In four cases the MPFL was partially dissected or perforated by a screw and fixed to the femur by the plate. The MCL was intact and not impinged by the implant in any case. In total four of eight knees the capsule was transected or perforated by a screw or by a part of the plate, resulting in intraarticular implant placement.

CONCLUSIONS

Standard plate placement during TH on the distal medial femur frequently leads to damage to the MPFL, impingement of the MPFL, the capsular and synovial tissues or exposure of the knee joint.

Phenomenon of painless knee in recurrent patellar dislocation in children

INTRODUCTION

Cartilage lesion with patellar malalignment may be correlated with pain. Situations in which patients with recurrent patellar dislocation are painless between episodes of luxation can be approached with considerable curiosity. We evaluated the distribution of substance-P and S-100 protein expression in soft tissue of the knee in children with recurrent patellar dislocation, in order to evaluate the distribution of nociceptors and determine tissue origins of this situation.

MATERIAL AND METHODS

Samples were collected from the medial and lateral synovial membrane, medial and lateral patellar retinaculum, Hoffa's body, patellar ligament, and quadriceps' aponeurosis in 10 children during the Blauth procedure and 10 adults with idiopathic osteoarthritis during total joint alloplasty. The density of nociceptive fibres was compared in the children and adults using S-100 and substance-P monoclonal antibodies.

RESULTS

Statistical differences between groups were demonstrated for S-100 expression in synovial membrane of the medial knee compartment (p < 0.05) and for substance-P expression in the medial patellar retinaculum (p < 0.05) and synovial membrane of the lateral (p < 0.05) and medial (p < 0.05) knee compartment in favour of children.

CONCLUSIONS

Lack of pain sensations in patients with recurrent patellar dislocation may be associated with non-increased expression of nerve endings in Hoffa's body. Increased expression of either S-100 protein or substance-P in synovial membrane and the medial retinaculum did not induce pain development in the knee joints of that group of patients.

Exercise and osteoarthritis: cause and effects

Osteoarthritis (OA) is a common chronic joint condition predominantly affecting the knee, hip, and hand joints. Exercise plays a role in the development and treatment of OA but most of the literature in this area relates to knee OA. While studies indicate that exercise and physical activity have a generally positive effect on healthy cartilage metrics, depending upon the type of the activity and its intensity, the risk of OA development does appear to be moderately increased with sporting participation. In particular, joint injury associated with sports participation may be largely responsible for this increased risk of OA with sport. Various repetitive occupational tasks are also linked to greater likelihood of OA development. There are a number of physical impairments associated with OA including pain, muscle weakness and altered muscle function, reduced proprioception and postural control, joint instability, restricted range of motion, and lower aerobic fitness. These can result directly from the OA pathological process and/or indirectly as a result of factors such as pain, effusion, and reduced activity levels. These impairments and their underlying physiology are often targeted by exercise interventions and evidence generally shows that many of these can be modified by specific exercise. There is currently little clinical trial evidence to show that exercise can alter mechanical load and structural disease progression in those with established OA, although a number of impairments, that are amenable to change with exercise, appears to be associated with increased mechanical load and/or disease progression in longitudinal studies.

Biomechanical evaluation of augmented and nonaugmented primary repair of the anterior cruciate ligament: an in vivo animal study

PURPOSE

The purpose of this study was to evaluate in a sheep model the biomechanical performance of augmented and nonaugmented primary repair of the anterior cruciate ligament (ACL) following transection at the femoral end during a 12-month postoperative observation.

METHODS

Forty sheep were randomly assigned to nonaugmented or augmented primary ACL repair using a polyethylene terephthalate (PET) band. At two, six, 16, 26 and 52 weeks postoperatively four sheep in each group were sacrificed and biomechanical testing performed.

RESULTS

Compared with nonaugmented primary ACL repair, the PET-augmented repair demonstrated superior biomechanical results from 16 weeks postoperatively onwards in terms of anterioposterior (AP) laxity, tensile strength and ligament stiffness. The augmentation device works as a stress shield during the ligament healing process. The nonaugmented ACL repair also resulted in ligament healing, but the biomechanical properties were at a significantly lower level.

CONCLUSION

These results support the previously reported histological findings following augmented primary ACL repair. This animal study on the healing capacity of the ACL may provide some important contributions to how primary healing in certain types of ruptures can be achieved.

CLINICAL RELEVANCE

I.

Animal models for meniscus repair and regeneration

The meniscus plays an important role in knee function and mechanics. Meniscal lesions, however, are common phenomena and this tissue is not able to achieve spontaneous successful repair, particularly in the inner avascular zone. Several animal models have been studied and proposed for testing different reparative approaches, as well as for studying regenerative methods aiming to restore the original shape and function of this structure. This review summarizes the gross anatomy, function, ultrastructure and biochemical composition of the knee meniscus in several animal models in comparison with the human meniscus. The relevance of the models is discussed from the point of view of basic research as well as of clinical translation for meniscal repair, substitution and regeneration. Finally, the advantages and disadvantages of each model for various research directions are critically discussed.

Patellofemoral pain: an update on diagnostic and treatment options

Patellofemoral pain is a frequent and often challenging clinical problem. It affects females more than males and includes many different pathologic entities that result in pain in the anterior aspect of the knee. Diagnosis of the specific cause of pain can be difficult and requires assessment of lower extremity strength, alignment, and range of motion, as well as specific patella alignment, tracking, and mobility. The treatment for patellofemoral pain is usually conservative with anti-inflammatory medications, activity modification, and a specific physical therapy program focusing on strengthening and flexibility. Infrequently, surgical treatment may be indicated after a non-operative program fails. The outcomes of surgical management may include debridement, lateral release, and realignment of the extensor mechanism to unload the patellofemoral articulation are favorable.

The efficacy of patellar decompression for improving anterior knee pain following total knee arthroplasty without patellar resurfacing

BACKGROUND

Anterior knee pain remains common following total knee arthroplasty (TKA). In this study, we evaluated the efficacy of patellar decompression via drilling for the treatment of anterior knee pain following TKA without patellar resurfacing.

METHODS

A prospective cohort study was performed in 271 consecutive patients who underwent primary total knee replacement with patellar decompression (study group, n = 131) or without decompression (control group, n = 140). The patients were assessed according to the Knee Society rating, clinical anterior knee pain score, and British Orthopaedic Association patient-satisfaction score in each group. Each assessment was performed without the examiner knowing whether the patella had been decompressed. Radiographic evaluations were also performed according to the Knee Society scoring system for functional activity and our own severity grade system for patellofemoral articular change.

RESULTS

There were no adverse events following patellar decompression. The overall prevalence of anterior knee pain was not significantly different between groups (p = 0.71). However, patients presenting pain over grade II after the operation in the study group were statistically low (p = 0.01). The overall postoperative knee scores were higher in the study group, but there were no significant differences between groups (p = 0.0731). Analyses of the radiographs revealed similar postoperative outcomes in both groups of knees.

CONCLUSIONS

As we observed significantly lower rates of anterior knee pain and no patellar complications following patellar decompression via drilling in TKA without patellar resurfacing, we recommend performing patellar decompression in cases of total knee replacement without patellar resurfacing.

Regenerative injection therapy for osteoarthritis: fundamental concepts and evidence-based review

Regenerative therapy involves the injection of a small volume of solution into multiple sites of painful ligament and tendon insertions (entheses) and adjacent joint spaces, with the goal of reducing pain and ostensibly promoting tissue repair and growth. Dextrose and platelet-rich plasma solutions have been shown to increase expression of growth factors in vivo and have shown promising clinical results in the treatment of tendinosus. In the treatment of osteoarthritis, small clinical trials and case series to date suggest safety, symptomatic improvement, and functional improvement at up to a year of follow-up; however, most of these studies are uncontrolled. Given the methodological limitations of clinical research on regenerative injections for osteoarthritis to date, this treatment should be considered only after execution of a comprehensive assessment and treatment plan, including optimization of biomechanics, weight loss, cardiovascular exercise, resistance training, and judicious use of more established topical, oral, and injectable medications.

Management of a difficult knee problem

Chronic disabling patellofemoral (PF) pain and instability can have significant effects on patient function and lifestyle. Although the management of PF pain has improved greatly, there is still a category of patient who tends to have recalcitrant symptoms, which are difficult to manage. The patient often bounces from practitioner to practitioner, physiotherapist as well as surgeon, for some relief of symptoms. However, often the underlying source of the pain is not well understood, so treatment can aggravate the symptoms. The following case report demonstrates the effectiveness of physiotherapy in managing a complex clinical case of a 40 year old patient with bilateral PF symptoms of severe right knee pain and a subluxing left patella, as well as left hip pain. Some background is given as to the source of the right knee pain with magnetic resonance imaging (MRI) supporting the diagnosis and treatment progression. The initial MRI demonstrated marked redundancy of the patellar tendon, resulting in patella baja (infera). Two years and ten treatments later, the patient, who originally could barely walk, was playing tennis for the first time in 25 years. Her MRI showed a complete resolution of the patella baja (infera), indirectly implying an improvement in quadriceps tone, as well as, resolution of the subchondral bone marrow oedema at the lateral patellar facet. Physiotherapists should not give up on patients with chronic musculoskeletal conditions as much can be done for them. These patients need clinicians to persevere, because certainly, for both patient and therapist, the rewards are great.

Nociceptive sensory innervation of the posterior cruciate ligament in osteoarthritic knees

INTRODUCTION

Although the posterior cruciate ligament (PCL) is considered to contain not only proprioceptive but also nociceptive sensory fibers, there is a lack of information about nociceptive sensory innervation of the PCL. We hypothesized that the PCL has constant nociceptive sensory innervation, suggesting the possible source of osteoarthritic (OA) knee pain.

MATERIALS AND METHODS

Innervation of the PCL was examined by immunohistochemistry with particular reference to nociceptive nerve fibers in OA knees. Sensory nerve fibers were semi-quantitatively counted in the PCL of OA knees, comparing with non-OA knees. Protein gene product 9.5 (PGP9.5) as a general neuronal marker and calcitonin gene related peptide (CGRP) as a marker for nociceptive neuron were used.

RESULTS

The PCLs had constant CGRP-immunoreactive (IR) nerve fibers in both OA and non-OA knees. The difference of the CGRP-IR nerve density between groups did not reach a statistical significance (p = 0.062). For PGP9.5-IR nerve fibers, however, the PCLs in OA knees were statistically less innervated than non-OA knees (p = 0.0009).

CONCLUSIONS

Our results showed that, in spite of a significant decrease in total innervation in OA knees, the PCLs have constant nociceptive sensory innervation. Although the relationship between the decrease in total innervations in the PCL and OA pathophysiology is still unclear, the PCL is the possible source of OA knee pain. Our results should be taken into account when examining the pain source of the OA knees and handling the PCL during total knee arthroplasty.

Open lateral patellar retinacular lengthening versus open retinacular release in lateral patellar hypercompression syndrome: a prospective double-blinded comparative study on complications and outcome

PURPOSE

To compare complication rates and outcome of open lateral retinacular (LR) lengthening and open LR release in the treatment of lateral patellar hypercompression syndrome (LPHS).

METHODS

In a prospective double-blinded study, 28 patients (mean age, 48 years; 21 women and 7 men) received either LR release (14 patients) or LR lengthening (14 patients) in alternating fashion over the same lateral parapatellar skin incision for LPHS (blinding of patients to surgical procedure [i.e., single blinding]). Strict inclusion criteria (retinacular pain, tight retinaculum, decreased patellar mobility) were used to exclude other reasons for anterior knee pain (patellar instability, leg malalignment or maltorsion, trochlear dysplasia, patella alta). The surgeon and postsurgical rehabilitation were the same. Preoperatively and at 3, 6, 12, and 24 months postoperatively, complications, muscle atrophy, and Kujala patellofemoral outcome score were documented by examiners blinded to the surgical procedure (double blinding). All patients completed 2 years of follow-up.

RESULTS

The results of 2 years of follow-up showed that recurrence of LPHS, as indicated by the patellar tilt test and decreased medial patellar glide test, developed in 2 cases after LR release and 1 case after LR lengthening (P > .999). Medial patellar subluxation, as indicated by the gravitation-subluxation test and increased medial patellar glide test, developed in 5 cases after LR release and no case after LR lengthening (P = .041). Quadriceps atrophy, as indicated by the mean circumference difference compared with the healthy contralateral side, was significantly higher (P = .001) in the LR release group (1.8 cm) than in the LR lengthening group (0.2 cm). The mean Kujala score was significantly lower (P = .035) in the LR release group (77.2 points) than in the LR lengthening group (88.4 points).

CONCLUSIONS

In this prospective double-blinded study, retinacular lengthening showed less medial instability, less quadriceps atrophy, and a better clinical outcome at 2 years compared with retinacular release. We believe that this may be explained by the controlled preservation of the lateral patellar muscle-capsuloligamentous continuity after retinacular lengthening.

LEVEL OF EVIDENCE

Level II, prospective double-blinded comparative study.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

Evaluation and treatment of disorders of the infrapatellar fat pad

The infrapatellar fat pad (IFP), also known as Hoffa's fat pad, is an intracapsular, extrasynovial structure that fills the anterior knee compartment, and is richly vascularized and innervated. Its degree of innervation, the proportion of substance-P-containing fibres and close relationship to its posterior synovial lining implicates IFP pathologies as a source of infrapatellar knee pain. Though the precise function of the IFP is unknown, studies have shown that it may play a role in the biomechanics of the knee or act as a store for reparative cells after injury. Inflammation and fibrosis within the IFP, caused by trauma and/or surgery can lead to a variety of arthrofibrotic lesions including Hoffa's disease, anterior interval scarring and infrapatellar contracture syndrome. Lesions or mass-like abnormalities rarely occur within the IFP, but their classification can be narrowed down by radiographical appearance. Clinically, patients with IFP pathology present with burning or aching infrapatellar anterior knee pain that can often be reproduced on physical exam with manoeuvres designed to produce impingement. Sagittal MRI is the most common imaging technique used to assess IFP pathology including fibrosis, inflammation, oedema, and mass-like lesions. IFP pathology is often successfully managed with physical therapy. Passive taping is used to unload or shorten an inflamed IFP, and closed chain quadriceps exercises can improve lower limb control and patellar congruence. Training of the gluteus medius and stretching the anterior hip may help to decrease internal rotation of the hip and valgus force at the knee. Gait training and avoiding hyperextension can also be used for long-term management. Injections within the IFP of local anaesthetic plus corticosteroids and IFP ablation with ultrasound guided alcohol injections have been successfully explored as treatments for IFP pain. IFP pathology refractory to physical therapy can be approached through a variety of operative treatments. Arthroscopic partial resection for IFP impingement and Hoffa's disease has showed favourable results; however, total excision of the IFP performed concomitantly with total knee arthroplasty (TKA) resulted in worse results when compared with TKA alone. Arthroscopic debridement of IFP fibrosis has been successfully used to treat extension block following anterior cruciate ligament reconstruction, and arthroscopic anterior interval release has been an effective treatment for pain associated with anterior interval scarring. Arthroscopic resection of infrapatellar plicae and denervation of the inferior pole of the patella have also been shown to be effective treatments for refractory infrapatellar pain.

Approach to the active patient with chronic anterior knee pain

The diagnosis and management of chronic anterior knee pain in the active individual can be frustrating for both the patient and physician. Pain may be a result of a single traumatic event or, more commonly, repetitive overuse. "Anterior knee pain," "patellofemoral pain syndrome," and "chondromalacia" are terms that are often used interchangeably to describe multiple conditions that occur in the same anatomic region but that can have significantly different etiologies. Potential pain sources include connective or soft tissue irritation, intra-articular cartilage damage, mechanical irritation, nerve-mediated abnormalities, systemic conditions, or psychosocial issues. Patients with anterior knee pain often report pain during weightbearing activities that involve significant knee flexion, such as squatting, running, jumping, and walking up stairs. A detailed history and thorough physical examination can improve the differential diagnosis. Plain radiographs (anteroposterior, anteroposterior flexion, lateral, and axial views) can be ordered in severe or recalcitrant cases. Treatment is typically nonoperative and includes activity modification, nonsteroidal anti-inflammatory drugs, supervised physical therapy, orthotics, and footwear adjustment. Patients should be informed that it may take several months for symptoms to resolve. It is important for patients to be aware of and avoid aggravating activities that can cause symptom recurrence. Patients who are unresponsive to conservative treatment, or those who have an underlying systemic condition, should be referred to an orthopedic surgeon or an appropriate medical specialist.

Efficacy of immunohistological methods in detecting functionally viable mechanoreceptors in the remnant stumps of injured anterior cruciate ligaments and its clinical importance

PURPOSE

Various histological and immunological methods have been used to detect the mechanoreceptors and nerve fibers on the intact ACLs as well as on the remnant stumps. However, some of these methods lack standardization, and the variable thickness of slices used often leads to misinterpretation. The study was based on the hypothesis that immunohistological methods are easier and more reliable means to demonstrate mechanoreceptors in the remnant ACL stumps as compared with the conventional methods. We also attempted to validate the methodology of immunohistology as a means of characterizing functional mechanoreceptors in the residual stump of an injured ACL.

METHODS

The remnants of the ruptured ACL in 95 patients were harvested during arthroscopic ACL reconstruction and evaluated immunohistologically using hematoxylin and eosin (H&E), and monoclonal antibodies to S-100 and NFP. Multiple sections from each specimen were serially examined by two histologists.

RESULTS

The positivity of monoclonal antibody against NFP showed a statistically significant relationship with the presence of morphologically normal mechanoreceptors, whereas the positivity of monoclonal antibody against S-100 showed a statistically significant relationship with the presence of free nerve ending in the residual stump of an injured ACL.

CONCLUSIONS

Immunological methods are more reliable and easier to use as compared with the conventional methods of histological staining for identifying remnant stumps likely to be of some proprioceptive benefit after an ACL injury. Such an identification might help us preserve certain remnant stumps during ACL reconstruction which might in turn improve the postoperative functional outcomes.

Vastus medialis obliquus atrophy: does it exist in patellofemoral pain syndrome?

BACKGROUND

Quadriceps atrophy and in particular atrophy of the vastus medialis obliquus (VMO) muscle have been frequently related with patellofemoral pain syndrome (PFPS), despite very little objective evidence.

HYPOTHESIS

Patients with PFPS exhibit atrophy of the VMO in comparison with healthy controls.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Forty-six patients with PFPS and 30 healthy control persons with similar age, gender, body mass index, and activity index distributions underwent magnetic resonance imaging (MRI) of the quadriceps. The muscle size was determined by calculating the cross-sectional area of the total quadriceps and its components.

RESULTS

The cross-sectional area (CSA) of the VMO was significantly smaller in the PFPS group than in the control group (16.67 ± 4.97 cm(2) vs 18.36 ± 5.25 cm(2)) (P = .040). A tendency was noted for a smaller total quadriceps CSA for the PFPS patients at midthigh level (66.99 ± 15.06 cm(2) vs 70.83 ± 15.30 cm(2)) (P = .074).

CONCLUSION

This is the first study to examine VMO size in PFPS patients by MRI. Patients with patellofemoral problems exhibited atrophy of the VMO. Although it is not clear whether this atrophy is a result or a cause of PFPS, the results of this study do show that atrophy of the VMO is a contributing factor in PFPS. Longitudinal, prospective studies are needed to establish the cause-effect relation of VMO atrophy and PFPS.

Relation of discoid lateral meniscus and cord-like anterior intermeniscal ligament: morphological and clinical study

Discoid lateral meniscus is a rare disorder and its association with other variations in the knee joint has been reported. The anterior intermeniscal ligament has also been described as connecting the anterior convex margin of the lateral meniscus to the anterior horn of the medial meniscus. In the normal population, it was observed at 53-94%. Although the functional properties of the anterior intermeniscal ligament are not yet clarified, two distinct types of the ligament have been described according to their morphological characteristics as cord-like and membranous types. The purpose of this study was to evaluate any possible association between morphologic types of anterior intermeniscal ligament and discoid lateral meniscus. A retrospective study was designed; 20 discoid lateral menisci were operated using routine arthroscopic examination. Upon arthroscopic examination the thickness of the ligament and associated morphological changes were recorded systematically. The cord-like anterior intermeniscal ligament was an associated structure in 15 of the 20 knees with discoid lateral meniscus (75%). Patients with discoid lateral meniscus apparently have cord-like type anterior intermeniscal ligament, thus we conclude that cord-like type of anterior intermeniscal ligament is a frequent accompanying structure to discoid lateral meniscus and may have a potential stabilizing effect on its anterior stability.

Hoffa's fat pad impingement treated arthroscopically: related findings on preoperative MRI in a case series of 62 patients

INTRODUCTION

The morphology of painful impingement of the infrapatellar fat pad (Hoffa's disease), which is characterized by inflammation, swelling, hypertrophy, fibrosis, and/or calcifications, has been well described. The purpose of this study was to investigate whether corresponding characteristic MRI findings could be assessed in patients with infrapatellar fat pad impingement.

MATERIALS AND METHODS

This study includes 62 patients with secondary symptomatic Hoffa's fat pad impingement. In these patients, the fat pad was partially resected until no impingement could be determined at full knee movement. Within a maximum of 3 months before arthroscopic surgery, patients had standardized MR imaging using a 1.5 Tesla unit with the following sequences: sagittal T1-TSE, coronal STIR-TSE, transversal fat-suppressed PD-TSE, and sagittal fat-suppressed PD-TSE (Siemens Magnetom Avanto syngo MR B 15). In this case series, the preoperative MRI appearance of the fat pad was evaluated and compared with a cohort of 255 patients without fat pad impingement but with various knee disorders at arthroscopy as well as the same standardized MRI protocol.

RESULTS

In patients with Hoffa's fat pad impingement, morphologic changes such as localized edema of the superior and/or posterior part of the fat pad, a deep fluid-filled infrapatellar bursa, non-visualization of vertical and/or horizontal clefts, fibrosis, and calcifications were noted on MR imaging with remarkable frequency. Besides a significant enlargement of the fat pad, each of these MRI findings was significantly associated with impingement of Hoffa's fat pad (P < 0.05). Besides a moderate kappa score for the detection of intrahoffatic calcifications and vertical clefts, kappa values for each finding showed good inter-observer agreement. Results of logistic regression revealed that edema of Hoffa's fat pad was one of the most important diagnostic MRI criteria for the diagnosis of Hoffa's fat pad impingement.

CONCLUSION

MR imaging allows identification of several changes that may be related to a symptomatic impingement of Hoffa's fat pad. In patients who are suspected of having infrapatellar fat pad impingement, such MRI findings should be considered and distinguished from other causes of anterior knee pain.

The reliability of a method for measuring the anterior cruciate ligament-hamstring reflex: an objective assessment of functional knee instability

Anterior cruciate ligament (ACL) rupture leads to mechanical and functional knee instability. Functional instability is likely attributable to a sensorimotor deficit. In previous studies, a method has been introduced which allows this deficit to be objectively assessed using ACL-hamstring reflex measurements. There is evidence that subjectively stable and unstable patients with ACL rupture can be objectively distinguished by this method. This study on 34 men was conducted to investigate the reliability of this method on the basis of several factors (intra-individual reproducibility, side-to-side differences, inter-examiner reliability, audiovisual stimuli, fatigue, height, weight, physical fitness, and level of activity at work). The role of gender was assessed in 20 men and 20 women. None of the factors had a relevant influence on reflex responses. The tests were reproducible and reliable. The method described here can thus be used for further research and the clinical diagnosis of functional instability following ACL rupture.

Immunohistochemical study of mechanoreceptors in the tibial remnant of the ruptured anterior cruciate ligament in human knees

This study was performed to identify the mechanoreceptors in the tibial remnants of ruptured human anterior cruciate ligaments (ACL) by immunohistochemical staining. Thirty-six specimens of tibial ACL remnants were obtained from patients with ACL ruptures during arthroscopic ACL reconstruction. As control, two normal ACL specimens were taken from healthy knee amputated at thigh level due to trauma. The specimen was serially sectioned at 40 mum. In control group, the average number of sections per specimen was 132, and a total of 264 slices were available. In remnant group, the average number of sections per specimen was 90, and a total of 3,251 slices were available. Immunohistochemical staining was performed to detect the neural element of mechanoreceptors. Histologic examinations were performed under a light microscope and interpreted by a pathologist. Nineteen (8 Ruffini, 11 Golgi) mechanoreceptors were identified in the two normal ACLs, which were evenly distributed at both tibial and femoral attachments. In the remnant group, mechanoreceptors were observed in 12 out of 36 cases (33%), and a total of 17 (6 Ruffini and 11 Golgi) mechanoreceptors observed. No significant differences in the harvest volume, number of sections, age, or time between injury to surgery was observed between the 12 mechanoreceptor-present and the 24 mechanoreceptor-absent ones. The presence of mechanoreceptor at the tibial remnants of torn ACLs was verified. The immunohistochemical staining methodology proved useful, but requires further refinement. Although the mechanoreceptors were detected relatively less frequently than expected, the authors consider that it does not negate the necessity of remnant-preserving ACL reconstruction.

Histological evaluation of the healing potential of the anterior cruciate ligament by means of augmented and non-augmented repair: an in vivo animal study

The purpose of this animal study was to investigate the healing potential of the anterior cruciate ligament following transaction at the femoral end, by means of both the augmented and the nonaugmented primary repair, focusing on the histological changes during a 12-month postoperative observation period with respect to necrosis and the loss of normal structures during the healing period. Twenty sheep were randomly assigned to nonaugmented primary ACL repair, or to augmented ACL repair using a polyethylene terephthalate (PET) band. At 2, 6, 16, 26 and 52 weeks postoperatively four sheep out of each group were sacrificed. Histological healing was achieved after 16 weeks for the augmented repair group and after 26 weeks for the nonaugmented repair group. The main difference between the two techniques was that the PET augmentation device protected the ligament from necrosis and ligamentization. In this group a consistently normal ligament was seen histologically during the entire postoperative observation period. The nonaugmented repaired ACLs underwent the processes of necrosis and ligamentization.