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Knee injuries continue to present a complex set of clinical problems. The answers to these problems have recently been redefined by the application of sophisticated biomechanical research methods to the study of knee ligaments and joint function. This manuscript reviews contributions which our laboratory has made to the understanding of knee injury, highlighting those research findings which form the basis for our clinical treatment of knee ligament injuries. High strain-rate techniques for studying knee ligament failure have replaced the previous low strain-rate methods and distinguish the failure mechanism of ligaments from that of bone. Ligament function is now further defined by measuring the restraining force provided by specific ligaments, adding to the information provided by cutting studies. The development of the 6-degrees-of-freedom concept and the instrumented kinematic chain now permit precise analysis of joint position, motion, and laxity. Biomechanical evaluation of intra-articular anterior cruciate ligament substitution has emphasized the importance of selection of a high-strength graft material, meticulous surgical technique with attention to graft vascularity, precise location of graft fixation sites, judicious adjustment of graft tension, post-operative protection during tissue remodelling, and a carefully conceived rehabilitation program. Newer biomechanical research methods have provided a sound scientific foundation on which to base clinical decisions concerning the care of knee ligament injuries.

Autogenous tendon and fascia are the most commonly used grafts for anterior cruciate ligament (ACL) reconstruction. Allografts, however, are now being used in selected patients. Allografts offer the advantage of decreased surgicaltime and morbidity, and a wider choice of graft type, size, and shape. The purpose of this study was to determine the inherent mechanical properties of sterilely procured/ freeze-dried (SP/FD), ethylene oxide/freeze-dried (ETO/FD), and irradiated/ freeze-dried (IRR/FD) fascia lata specimens and to compare the results to freshfrozen (FF) fascia data from our previous study (Noyes et al. 1984).

The complete tear of the anterior cruciate ligament initiates the clinical syndrome represented by continued functional disability. The precise degree of functional disability is highly debated. Agreement is elusive due to the lack of uniform and scientific methodology. An historical review and analysis of functional and subjective rating systems is reported, and the strengths of previous systems are identified. A subjective and functional rating system is proposed in which 6 activity levels are related to pain, swelling, giving-way and overall activity. This is important because of the marked dependence of the functional disability of the anterior cruciate insufficient knee on the activity level of the patient. Thus, activity levels must be rigorously and comprehensively defined. In addition, we propose the utilisation of a risk factor checklist, based on the statistics drawn from our previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofemoral factors, rehabilitation and patient compliance. Thirdly, we examine controversial aspects of the anterior cruciate ligament syndrome existing in the literature today and demonstrate why contrasting opinions are not mutually exclusive. Finally we propose our treatment guidelines for management of the acute and chronic anterior cruciate ligament insufficient knee.

Computerized thermography was used to evaluate 17 patients diagnosed with patellar tendinitis. The intent of this study was to determine if a specific patellar tendinitis thermal pattern could be distinguished using infrared thermography. A specific thermal abnormality was found over the patellar tendon in 14 subjects (78%). Twelve subjects showed focal "hot" spots, while two showed focal "cold" spots. The thermal abnormalities appeared as specific focal areas directly overlaying the patellar tendon, without disruption to the thermal pattern of the remaining peripatellar regions. The thermal gradient slope over the patellar tendon was greater in symptomatic knees. Five subjects returned 2-4 weeks later for follow-up thermographic examination. Among the follow-up subject group, changes in thermal asymmetry correlated with changes in symptoms 80% of the time. Computerized thermography appears useful as a noninvasive, objective method of detecting inflammation of the soft tissues about the patellar tendon, and also helps to differentiate this disorder from other knee pathologies. J Orthop Sports Phys Ther 1987;9(4):132-140.

The hypothesis proposed in this study was that the initiation of active and passive knee motion within 48 hours of major intraarticular knee ligament surgery would not have the deleterious effects of increasing knee effusion, hemarthrosis, periarticular soft tissue edema, and swelling. We conducted a prospective study with randomized assignment of 18 patients into two groups: 9 patients in the "motion" group began 10 hours of daily continu ous passive motion (CPM) on the 2nd postoperative day, while the remaining 9 in the "delayed motion" group used a soft hinged knee brace with knee hinges locked at 10° of flexion and entered into the motion program on the 7th postoperative day. All knees were allowed full 0° to 90° of motion except for a total of seven knees with concomitant mensicus repairs and extraar ticular reconstructions where 20° to 90° of motion was allowed, limiting the last 20° of knee extension for the first 4 postoperative weeks to protect the repair. In all other respects, the rehabilitation program after surgery was the same for the two groups, including postoper ative compression dressings, exercises, and weight- bearing status. Ten of the eighteen patients had acute ACL disrup tions and 8 had chronic ACL insufficiencies. There was an even distribution of acute and chronic knee cases and of open and arthroscopic ligament procedures in the early and delayed motion groups. Associated sur gery included four meniscus repairs, three medial col lateral ligament repairs, and one lateral collateral liga ment repair. Special suturing and fixation techniques were used at surgery to maintain the integrity of liga ment and meniscus structures, allowing the surgeon to feel safe in subjecting the joint to early postoperative motion. The objective parameters measured were KT- 1000 arthrometer measurements, Cybex isokinetic testing, girth measurements at four lower limb loca tions, range of motion goniometer measurements, post operative pain medications, and days of hospitalization. Starting intermittent passive motion on the 2nd post operative day did not increase joint effusion, hemar throsis, or soft tissue swelling. In both motion groups, postoperative joint effusions were absent after the 14th postoperative day. There was no statistically significant difference in knee extension or flexion limits, pain med ication used, or hospital stay in comparing the two knee motion programs. An important finding of this study was the significant decreases in thigh circumference that occurred within the first few weeks of surgery, which progressed de spite a closely supervised inpatient and outpatient re habilitation program. The decreased thigh girth was related to the type of operative procedure. Arthroscopic reconstructions had only 25% to 38% of the loss of thigh girth found in open operative procedures. By the 7th postoperative day, the average circumference loss for the open reconstruction group (motion at 7th post operative day) was nearly 4 cm, compared with the arthroscopic group's average of 1 cm. By the 21 st postoperative day, all patients who underwent open procedures sustained an average of 6.5 cm thigh cir cumference decrease compared with a 2 to 3.5 cm loss in the arthroscopic group. We concluded that traditional rehabilitation protocols are often ineffective in prevent ing the significant quadriceps muscle atrophy that may occur within the first few days of surgery. Of importance was the finding that initiating early knee motion did not stretch out ligamentous recon structions. We strongly recommend an early motion program to decrease the morbidity of major intraarti cular ligamentous procedures. The program is initiated within the hospital setting immediately after knee sur gery.

During flexion of the intact knee, we measured the changes in distance between possible tibial and femoral attachments of an intraarticular ACL substitute. The change in distance during motion was described by the difference between the longest and shortest distances measured. Using knees from eight cadaver donors, we studied the effects of varying tibial and femoral attach ment locations, applying anterior and posterior forces, and altering the range of flexion. We found that altering the femoral attachment had a much larger effect than had altering the tibial attach ment. No femoral attachments were completely iso metric. Femoral attachments that produced the small est change in tibiofemoral distance, 2 mm and less, formed a band whose greatest width ranged from 3 to 5 mm. The axis of the 2 mm region was nearly proximal- distal in orientation and located near the center of the ACL's femoral insertion. Attachments located anterior to the axis moved away from the tibial attachment with flexion, whereas attachments located posterior to the axis moved toward the tibia. The AP position of the tibial attachment affected the orientation of the 2 mm region. Moving the tibial attach ment posteriorly caused the proximal part of the region to move anterior, with little change in the location of the distal part of the region. Changing the applied joint force from anterior to posterior was similar to moving the tibial attachment posteriorly, but the effect was less pronounced. Increasing the range of flexion from 90° to 120° caused the 2 mm region to become narrower and changed its orientation.

The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma-ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes in the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.

It is increasingly accepted that successful reconstruction of the anterior cruciate ligament requires selecting an attachment location and method of tensioning that restores normal joint laxity without subjecting the substitute to large forces during flexion-extension motions. This can be accomplished by either “over the top” placement or use of an intra-articular drill hole located to produce minimal stretching of the substitute.

In the past ten years there has been increased use of six-degree-of-freedom instrumented spatial linkages for the measurement of biological joint motions. In spite of the increased popularity, little information has been reported on the accuracy of these devices. In this paper, we present a two-part investigation of the accuracy of the instrumented spatial linkage when used to measure knee joint kinematics. In the first part, we present the results of a theoretical analysis and an experimental determination of the errors associated with spatial linkage systems. In the second part, we describe the errors associated with a bi-planar X-ray system used to obtain the coordinate transformation between the linkage ends and coordinate systems located in the bones comprising the joint. We found that the theoretical error analysis consistently overestimated the actual measurement error, thus providing an unreliable estimate of errors. The experimental study of both the linkage system and the bi-planar X-ray system demonstrated that the accuracy of displacement measurement is insensitive to large systematic errors in position measurement.

The three rotations and three translations that comprise total knee motion were simultaneously measured in cadaveric knees during the commonly employed clinical tests for anterior cruciate injury. A second study determined the three-dimensional motions that occurred when known forces and moments were applied. A total of eight whole lower limbs were studied. A 6 degree-of-freedom instrumented linkage (3-D electrogoniometer), rigidly mounted to the tibia and femur, was used. The ligaments sectioned included the lateral extraarticular restraints (iliotibial band, lateral capsule) and the anterior cruciate ligament, both separately and in combination. After sectioning the anterior cruciate ligament alone, anterior displacement of both the medial and lateral tibial condyles increased markedly during the flexion rotation drawer and pivot shift tests. At 30 degrees knee flexion, total anterior-posterior displacement increased 100 percent, but internal-external tibial rotation increased only 15 percent. In all the anterior displacement type of clinical tests (including Lachman's test), there was not a true rigid coupling of knee motions because the examiner controlled the amount of internal tibial rotation and anterior tibial translation. After anterior cruciate sectioning alone, both the lateral and medial tibial condyles displaced anteriorly. Sectioning the medial structures caused additional anterior translation of the medial and lateral tibial condyles. We measured many different combinations of motions that depend on the ligament and capsular structures injured, the clinical test used, and how the clinician performed the test. Differing types of anterior subluxation require that the separate subluxations of the medial and lateral tibial condyles be determined during each stress test.

This study reports on the disability of 103 patients with symptomatic chronic laxity of the an tenor cruciate ligament that was uncomplicated by other associated major ligament deficiency or prior lig ament reconstructive procedures. All of the patients were evaluated at an average of 5.5 years after injury but a subgroup of thirty-nine patients was evaluated at an average of 11.2 years after injury. All had been ac tive in sports, with two-thirds participating in high school or college athletics. The diagnosis of a tear of the anterior cruciate ligament was made by the original treating physician in only seven (6.8 per cent) of the 103 knees. Sixty-four patients (62 per cent) stated that the pain that followed the injury restricted normal ac tivities for longer than three weeks. Eighty-five patients (82 per cent) had returned to some form of sports ac tivity. This gave a false initial impression that the in jury was not eventually disabling for sports, as a sig nificant reinjury occurred in thirty-six patients (35 per cent) within six months and in fifty-three patients (51 per cent) within one year after the original injury. At follow-up five years later, only thirty-six patients (35 per cent) were participating in strenuous sports. A significantumber of patients withlonger follow-up had knee symptoms that affected their routine daily and recreational activities. A subjective moderate to severe over-all disability was reported by thirty-two patients (31 per cent) for walking activities alone, by forty-five patients (44 per cent) for over-all routine activities of daily living, and by seventy-seven patients (74 per cent) for turning or twisting sports ac tivities. Pain occurred in thirty-one patients (30 per cent) during walking activities, in forty-eight patients (47 per cent) during recreational activities, and in seventy-one patients (69 per cent) during strenuous sports activities. Twenty-two patients (21 per cent) complained of giving-way during walking activities; thirty-four patients (33 per cent), during recreational sports; and sixty-six patients (65 per cent), during 4 Supported in part by National Institutes of Health Grants AM2I 172 and AM27517 from the Musculoskeletal Disease Program of the National Institute of Arthritis, Diabetes, Digestive and Kidney Dis eases. t Cincinnati Sports Medicine and Orthopaedic Center, 1 Lytle Place, Cincinnati, Ohio 45202. @ Department ofOrthopaedic Surgery, Hospital ofthe University of Pennsylvania, 3400 Spruce Street, Philadelphia, Pennsylvania 19104. §Department of OrthopaedicSurgery,Universityof Pittsburgh, Pittsburgh, Pennsylvania 15213. strenuous sports. Joint swelling occurred four to five times as frequently in the patients who had had the in jury for the longest time (average, 11.2 years). If the patient had had a meniscectomy, there was a statisti cally significant twofold to fourfold increase in symp toms of pain and swelling related to activity. Giving way was not affected, as this is related to instability of the anterior cruciate ligament. Significant roentgeno graphic changes of arthritis were noted in nineteen (21 per cent) of ninety-one patients starting at an average of 109 months after injury. Seventeen patients (44 per cent) in the subset with the longest follow-up had sig nificant roentgenographic changes. These changes cor related statistically with participation in strenuous sports activities, with running activities, and with giving-way. Important qualifications to this retrospective study are: (1) the patients studied were limited to those with tears of the anterior cruciate ligament who sought treatment for relief of their symptoms, (2) these pa tients continued to be active athletically and thus con tinued to abuse their knees, and (3) none of the patients had had proper initial treatment, rehabilitation, or counseling which might have prevented joint deterio ration. As a whole, the results show the significant functional disability found in the patient with a symp tomatic anterior cruciate-deficient knee, initially for sports activities but later, following reinjury, for meniscal damage, joint arthritis, and the activities of daily living. A dilemma still exists concerning the proper treat ment of a knee with a deficient anterior cruciate ligament, largely because of a lack of knowledge of the extent of the functional disability caused by such an injury'5'8'9―2―@ 21.23.25.27 Our goal was to study a sufficient number of pa tients whose knees demonstrated anterior cruciate laxity alone, without the superimposed variables introduced by previous operative procedures or complicated by other types of ligament instability. The study group also had to contain a sufficient number of patients whose injuries had been sustained at least five years and ten years previously, to allow statistical evaluation of long-term disability. Of importance in this study, as contrasted to many prior studies, is the rigorous grading of symptoms and their severity as related to the specific type of activity during which they occurred. 154 THE JOURNAL OF BONE AND JOINT SURGERY on December 4, 2006 www.ejbjs.org Downloaded from THE SYMPTOMATIC ANTERIOR CRUCIATE-DEFICIENT KNEE 155 years earlier (range, three months to 33.3 years). Twelve patients had been injured one year earlier and thirty-three, two years earlier. For a portion of the analysis, the group was divided into sixty-four patients who had been injured less than five years earlier and thirty-nine patients who had been injured at or more than five years earlier. The symptoms of pain, swelling, and giving-way were ranked as slight, moderate, or severe, as follows: slight —? occasional recurrent minor discomfort, not inter fering with activity; moderate —? symptoms usually brought on by an activity, interfering with activity, and relieved by stopping activity or rest; and severe —? symp toms occurring with activity, persisting and lasting over night or days, significantly interfering with activity (usu ally the patient must stop activity). Of the 103 patients in this study, fifty-one had had a meniscectomy, including six patients who had two menis cectomies. A total ofsixty-five menisci had been removed, of which forty-seven were medial, thirteen were lateral, and five were unknown. Fourteen patients had had both menisci removed. Fourteen meniscectomies had been per formed within three weeks after the initial injury and thirty-seven, within one year after injury. The remainder of the procedures were distributed throughout the remain ing years. Roentgenograms of ninety-one of the 103 knees were graded for degenerative arthritic changes, as follows: mm imum —? squaring of femoral and tibial margins, sub chondral sclerosis, no joint narrowing, and no significant osteophyte formation; moderate —? narrow joint-cartilage space, significant subchondral sclerosis, and osteophyte formation; or severe —? the aforementioned criteria plus obliteration of the joint-cartilage space.

Significant fluid extravasation occurred in four knees undergoing arthroscopic meniscectomy. In one knee, a partial compromise of peripheral blood flow was transiently detected. In cadaver studies, with the joint only moderately distended, a mean pressure of 158 mm of mercury was measured. With flexion of the knee to 90°, a mean pressure of 216 mm of mercury was recorded and rupture of the synovial pouch occurred in all knees. The fluid extravasated into the thigh due to rupture of the suprapatellar pouch. Fluoresceine labeled saline was utilized to follow the course of the extravasated fluid. The saline was found to loculate about the superficial femoral artery, easily dissecting up to the femoral triangle. Elevated femoral artery pressures and quadriceps muscle interstitial pres sures were documented at a relatively early point during the course of fluid extravasation. A second pathway of extravasation of intraarticular fluid was by rupture of the semimembranous bursa. The saline then dissected beneath the pes anserinus and into the calf muscles. The study arrived at the following conclusions. First, fluid extravasation may initially occur in a subtle man ner. The surgeon should be aware of any lack of joint distension, increased fluid to distend the joint, or increased thigh tension during arthroscopy indicating extravasation. Second, joint distension should be avoided prior to knee flexion past 30 to 45° since the added compression on the fluid may easily rupture the synovial pouch. Third, caution is required in using inflow irrigation systems that exert pressure to distend the joint; an adequate outflow system is mandatory to avoid excessive joint distension during arthroscopic procedures.

A combined experimental and clinical study relative to the production of spinal in- juries common to the winter sport of snowmobiling indicates that snowmobile spinal injuries are a repeatable phenomenon with seats of the current design. The number of injuries appears to be growing rapidly with the increased popularity of the sport. However, the redesign of snowmobile and snowmobile susoension svstems should allow the elimination of these injuries for most practical conditions. A WITH THE increased popularity of snowmobi- ling an alarming and ever-increasing number of related injuries have occurred. Investiga- tions have compiled accident reports in an effort to document this problem (McLay et uf. 1970: Carlson, 1970). The more serious injuries include: multiple extremity fracture, traumatic amputations, skull fractures, facial and eye injuries. spinal injuries and even decapitation. The accident statistics indicate that compression fractures of the spine make up a particularly significant class of snow- mobile injuries (Withington, 1970; Chism, 1969). This study is presented to draw attention to the high risk of spinal injuries in snow- mobiling. Illustrative cases of spinal fractures from such injuries, treated or reviewed at The University of Michigan Medical Center are shown. Case # 1 CASE REPORTS

s 285 calculated by Newtonian mechanics, and the absolute angular velocity of the leg. Based upon the peak values of instantaneous power the observations suggest that the ability to produce muscular power across the knee joint was not a limiting factor over the range of motion examined.

All of the factors discussed here hopefully will increase the success rate of future intra-articular grafts. But it should not be supposed that the ideal ACL substitution answer is immediately forthcoming. Past experience points to the inherent difficulty of any potential solution and the need to progress in a rigorous scientific manner in the evaluation of the next wave of ligament substitutes. This article reports the utilization of an immediate protective motion program to avoid the problems of postoperative stiffness and lack of knee extension. It can not be stated with certainly whether the same program can be applied to free grafts or to those obtained from other sites. However, the avoidance of these problems will significantly lessen the morbidity of intra-articular reconstruction. The utilization of a vascularized patellar tendon hopefully will add another dimension to ACL replacement.

Design of a synthetic replacement or selection of a biologic substitute requires detailed knowledge of the mechanical properties of the normal ligament. Femur-anterior cruciate ligament-tibia unit (ACL) data have been frequently used for this purpose, although not always properly. Mechanical properties of the human ACL-bone unit are reviewed. Ligament stiffness, elongation, and energy results are based on grip-to-grip motion and thus include ligament and limited bone deformations. Maximum bone-ligament-bone force in young donors (1730 +/- 66N) is higher than reported previously and represents only ligamentous failures. Methods for measuring tissue dimensions are provided and must be duplicated for obtaining accurate material property data. Bone-ligament-bone strain data are higher than those in reports where midsubstance collagen strains are measured and differ from data obtained on isolated ligaments. The authors have examined many factors that affect ligament-bone unit response. Increasing age weakens the tissue-bone preparation, and only when testing is performed at high rates will ligamentous failures predominate. Use of the authors' data in prosthetic ligament evaluation requires that the material be selected based on ligament bundle properties, the prosthesis be examined under similar testing conditions, and anticipated functional loads and margins of safety be determined.

Existing published knee rating systems that assess sports participation, knee function, and subjective symptomatology following ligamentous surgical procedures were analyzed. Major errors in questionnaire design and data reduction have led to invalid conclusions. A questionnaire containing a minimum set of rating criteria was formulated to validly assess athletic participation before and after treatment or surgery. Select questions and a data reduction format were established to assess the intensity of sports participation, changes in sports participation, the variables that produced the changes, self-assessed functional limitations, and the ability to participate in different types of sports. A clinical trial of the questionnaire was performed on 59 patients. An interview conducted upon completion of the questionnaire enabled the authors to detect difficulties or inconsistencies in the responses to the questions. The design format described in this report forms the basis for a subjective evaluation of ligamentous surgery. A standard format for analysis of sports participation and knee function is proposed to aid investigators in comparing variations in clinical results.

Smallpox osteomyelitis (osteomyelitis variolosa) with gross clinical and radiologic deformities of the elbows, hands and feet occurred in a 53-year-old Vietnamese refugee. This disease, once common in Asia and Africa, may cause permanent damage to joints and growth centers in the course of the acute infection in childhood. The roentgenographic features are sufficiently diagnostic to exclude congenital dysplasia of the skeletal system, leprosy, or sequelae of thermal injury, and other joint disorders.

The effect of intra-articular corticosteroid injections (methylprednisolone acetate) on the mechanical properties of anterior cruciate bone-ligament-bone units was determined. Fifty-one wild rhesus animals provided 88 knee ligaments units that were loaded in tension to failure under fast strain-rate conditions. Alterations in ligament strength and load-elongation properties were found to depend upon corticosteroid dosage and time after injection. Fifteen weeks after the higher drug dosage (methylprednisolone acetate, 6 mg/kg; three injections, spaced weekly) significant decreases occurred in the maximum failure load (20%), energy absorption prior to failure (11%) and linear stiffness (11%) of the ligament unit. In contrast, only minimal non-significant alterations in ligament strength properties occurred at the higher drug usage after 6 weeks in a second group of animals. this strong time-dependence may partially explain the negative findings reported in short term studies. The higher drug dosage used is approximately 10 times an equivalent human dose on a body mass basis and indicates the ability of this class of drugs to significantly alter the mechanical properties of a ligament unity. A third group of animals received a total of two intra-articular coticosteroid injections (single injections spaced two weeks apart) at a dosage (0.6 mg/kg) equivalent to that commonly used clinically in humans. Statistically significant decreases occurred in maximum failure load (9%) and energy absorption (8%); however, this change is believed of little importance to the projected functional capacity of the ligament unit. No detectable systemic effect of the intra-articular corticosteroid injections was found on the mechanical properties of the ligament unit in the extremity opposite to that which received the drug injection. Histological examination after failure showed normal cellularity and staining characteristics of the ligament, fibrocartilage junction and underlying bone. No bone resorptive changes were observed beneath the ligament insertion site. Failure by a ligamentous mode remained the most common mechanism of specimen failure. Scanning Electron Microscopy showed failure of collagen fibers at multiple levels throughout the ligament indicative of a serial pull-apart failure process. A rich supply of vessels to the anterior cruciate ligament was demonstrated and failure of the vessels occured by a necking down process. Insofar as the results apply to humans, they infer the potential for high and frequent doses of intra-articular slightly soluble corticosteroids to produce alterations in ligament strength and function. A single intra-articular injection or one repeated at intervals of several months probably carries little risk to ligament properties.

A complete tear of the anterior cruciate ligament represents the initiation of a clinical syndrome characterized by a continuum of functional disability. The authors present here a risk factor checklist, based on statistics drawn from their previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofemoral factors, rehabilitation, and patient compliance. They also present their subjective and functional rating system in which six activity levels are related to pain, swelling, and giving way. The functional disability of the anterior cruciate insufficient knee is activity-level related. Thus, activity levels must be rigorously and comprehensively defined for adequate appreciation of the degree of existing disability. The authors also examined the reasons for the conflicting opinions on the functional disability of the anterior cruciate ligament syndrome that exists in the literature. Differences in subjective and objective rating systems; failure to specifically define preinjury and postinjury activity levels and associated symptoms; and different populations as to laxity, giving way episodes, and type of athletic activity (jumping, twisting activities versus light recreational pursuits) are but a few of the important differences that make comparisons between studies often invalid. Long-range treatment guidelines are necessary for management of the acute and chronic anterior cruciate ligament insufficient knee.

The patellar tendon offers a number of advantages (strength, location, bone-to-bone fixation, vascularity) as a tissue for intra-articular cruciate ligament reconstruction. The critical factor is to preserve the vascularity, thereby maintaining tendon viability and facilitating tissue remodeling. Laboratory studies on human cadaver knees were conducted to define the blood supply to the patella, and vascularity was assessed by blood flow studies in three animal species, including nonhuman primates. In humans, the patellar ligament receives blood anteriorly from the retinaculum and posteriorly from the fat pad, which is relatively smaller and less adherent than the fat pad in other animals. The medial third of the patellar tendon and its contiguous neurovascular pedicle were used in a vascularized patellar tendon reconstruction procedure. During a period of three years, reconstruction with the vascularized patellar tendon was performed in more than 100 patients. Although only 35 patients have been followed up for more than two years, the clinical results are encouraging. At present, however, the technique is not recommended for general use; the surgical procedure is demanding, and the ultimate clinical results may not warrant the extra effort required to perform the surgery as well as commit the patient to a long rehabilitation program.