Followup of the acute nonoperated isolated

Transcription

1 Followup of the acute nonoperated isolated anterior cruciate ligament tear* RICHARD J. HAWKINS, MD, FRCS(C), FACS, GARY W. MISAMORE, MD, AND THOMAS R. MERRITT, MD, FRCS(C) From the Division of Orthopaedics, Department of Surgery, St. Joseph s Hospital, University of Western Ontario, London, Ontario, Canada ABSTRACT This report is an attempt to analyze what happens to an isolated ACL tear that is treated nonoperatively. The results of 40 patients treated initially by nonoperative means for this injury and followed an average of 4 years are reported. A very small percentage of these patients had associated meniscal pathology. Secondary reconstructive surgery was necessary in 12 patients (30%). Primary meniscal tears were present in 4 of 25 knees (16%) and secondary meniscal tears occurred in an additional four of the patients. Giving way was a problem for 36 (86%) of the nonoperated patients, but pain and swelling were not significant problems for most. Full return to unlimited athletic activities was possible for only four (14%) of the patients. Objective signs of ACL insufficiency could be demonstrated on all patients upon clinical examination at followup. Overall grading of the knees revealed 87.5% fair or poor results. The best treatment of isolated ACL disruption remains controversial. Some authors have advocated nonoperative treatments while others support early operative intervention. 2,3,5,8,12,13,16,19 Whether early surgical repair or reconstruction of the disrupted cruciate ligament can significantly alter the long-term prognosis remains unproven. Authors supporting early surgical repair of the ruptured ligament report good results. However, followup in those reports is relatively short and no control groups are presented for comparison. Before any intelligent recommendations for surgery can be made, some understanding of the natural history of the injury must be known. Several reviews of patients with ACL injuries managed by * Presented at the AAOS Meeting, Atlanta, 1984 t Address correspondence and repnnt requests to Richard J Hawkins, MD, 450 Central Avenue, Suite 107, London, Ontano, Canada, N6B 2E8 205 nonoperative means have been published,2, 4, 6,7,14, 17,18 but none of those reports present a true natural history of isolated ACL insufficiency. Each report has some inherent shortcomings that can confuse the issue. Although purporting to present only isolated ACL injuries, some of the studies include patients with apparent combined knee instabilities (varus or valgus instability in addition to the ACL insufficiency).4,6,7,14 Short followup of many patients makes some results difficult to interpret.2, Some studies present heterogeneous patient groups in which patients treated by both nonoperative and operative means are included.2, By the retrospective nature and relatively biased patient selection process in some studies, patients who were having difficulties from their knee instability were selected, while patients who were doing well were possibly excluded., 14,17,18 Noyes et al.,17 along with McDaniel and Dameron,14 offer insight into natural history only insofar as their patients were referred because of late symptoms and were therefore already &dquo;selected out&dquo; due to their instability. Thus, a true natural history study of randomly selected patients with isolated ACL disruptions treated by nonoperative methods has not been published. This study was instituted in an attempt to discern some insight into the natural history of this injury and to analyze the incidence and significance of instability complaints, meniscal pathology, and later development of osteoarthritis. MATERIALS AND METHODS From 1976 to 1981, a study was undertaken at the affiliated hospitals of the University of Western Ontario to investigate what happens to an isolated ACL tear when it is treated nonoperatively. The majority of patients were followed by the senior author (RJH); however, the patients were recalled in a retrospective manner for review by the junior authors. To be included in this study all patients had to be seen initially during the acute postinjury period when the diagnosis of rupture of the ACL was established. Thirty of the

2 patients were seen within 48 hours following the injury. However, 10 of the 40 patients were seen between 1 and 4 weeks following the injury, when the patients and their doctors realized they had a fairly significant injury. Their presentation was because of pain and swelling. There was no past history of knee complaints nor any history of knee injury. The presence of any clinically associated ligamentous injuries about the knee resulted in exclusion from the study. That is, no patients demonstrated varus or valgus (or posterior) instability on clinical examination. The pivot shift phenomenon was considered the sine qua non of an ACL disruption. Examination without anesthesia was sufficient for diagnosis in 15 (37.5% ) of the patients, all of whom had positive Lachman, anterior drawer, and pivot shift maneuvers. These patients demonstrated anterolateral instability. On clinical examination there was no evidence of additional instability, particularly no evidence of lateral instability. Twenty-five (62.5%) of the patients were given a general anesthetic for examination, arthroscopy, arthrotomy, or some combination of those procedures. Under anesthesia, Lachman and pivot shift maneuvers were invariably positive; however, the anterior drawer maneuver was negative in two (13.3%) of the knees. Rupture of the ACL was confirmed in all 25 patients undergoing arthroscopic examination. Additional arthrotomy was performed in seven cases because of suspected meniscal pathology with confirmation of an acute ACL tear. These patients are included in the study because it was thought that the meniscal pathology and arthrotomy played a minor role in their subsequent course. All arthrotomies were performed in 1976 and 1977, before operative arthroscopy was performed by the senior author. A primary meniscal tear was found in 4 of 25 (16%) of the 40 knees. One medial tear was a peripheral detachment and was casted for 6 weeks (meniscal suturing was not done). The remaining three tears, two medial and one lateral, were midsubstance; partial meniscectomy was performed in two patients and a complete meniscectomy in one patient. Again, these patients were included because of their primary underlying ACL insufficiency. All patients were treated with an exercise program for strengthening of the hamstrings and quadriceps muscles under the supervision of a physiotherapist directed by the physician. The one patient treated with immobilization had leg raising exercise only. Rehabilitation was started as soon as the patient could comfortably perform the exercises. Bracing was recommended for most patients but only used by some. There were 31 males and 9 females. The average age was 22 years (range, 15 to 43 years). Only four patients were over age 30, while 17 were less than 20 years old. The mechanism of injury involved rotation in 37 knees. Of those that could accurately recall the rotation involved, 15 inferred that their tibia went into external rotation and only 9 into internal rotation. Thirty patients (75%) distinctly remembered hearing a &dquo;pop&dquo; in the knee at the time of injury. Twenty-eight patients (70%) reported significant swelling within 2 hours, and all had swelling within 12 hours. RESULTS Followup was greater than 2 years in all patients. Followup of the 28 nonreconstructed patients averaged 45 months (range, 24 to 79 months). Secondary surgery Of the 40 patients, 12 (30%) required late reconstruction for chronic ACL insufficiency in the form of &dquo;giving way.&dquo; The mean time from injury to reconstructive procedure was 33 months. The earliest reconstruction in this group was done 7 months following the initial injury. The average age for this reconstructed group was 18 years (range, 16 to 28 years). In comparison, the average age for the remaining 28 nonreconstructed patients was 23 years. This group of 12 reconstructed patients is included in the study, but references to them regarding natural history will consider their preoperative status only. This report does not concern itself with their surgical management and results. Four patients required operative intervention for secondary meniscal tears. Two of those were in the group requiring secondary reconstruction. The remaining two patients had partial medial arthroscopic meniscectomies. There were, of course, other patients in the series who could have had meniscal pathology. Perhaps it would be unfair to assume a normal meniscus in patients who did not come to reconstruction or athroscopy. Nonoperated results Instability of the knee was the most common complaint among the 28 nonoperated patients. This consisted of both giving way and mistrust. Twenty-four patients (86%) experienced problems with giving way of the knee, while only four (14%) had no feeling of instability. Three patients (11%) experienced giving way with routine nonstressful daily activities, and 16 (57%) experienced instability or giving way with athletic endeavors. Many patients, with the exception of the four that had no feelings of instability, voluntarily expressed that they were cautious in some of their maneuvers, particularly rotational, for fear that their knee would give way if they allowed those maneuvers to occur. Twenty-five patients (69%) suffered giving way only when pivoting on the affected extremity, one had giving way with sudden deceleration, and two had giving way either pivoting or decelerating on the affected extremity. There was a clear relationship between activity level and giving way: the more active the patient, the more giving way. Most of these patients also experienced mistrust, particularly with rotation. The 12 patients who had already come to reconstruction all had significant disability related to giving way and mistrust. This group of patients was athletically aggressive, and in each case the giving way and mistrust were hampering

3 207 their ability to perform athletically. Although giving way and mistrust are significant complaints in the overall group of patients, the degree to which it was a problem is very difficult to determine objectively. All 40 patients were asked to evaluate subjectively their injured knee in relation to its preinjury condition. Only three patients (11%) felt that their knee was as stable and functional as it had been before the injury. Twenty patients (50%) felt that their knee was somewhat less good but that they were getting by and functioning reasonably well and accepted their disability. Five patients (18%) felt that their knee function was poor and that the knee was a functional liability. The 12 operated patients fit into the last category; therefore, the overall number of patients that felt that their knee was a liability was 17 (42.5%). Of the 28 nonreconstructed patients, successful participation in full sporting activities at the preinjury level was uncommon. Only four patients (14%) were able to resume and continue the same level of sports in which they participated before their knee injury. Twelve patients (43%) were still playing the same sports but with some limitations, and by the patient s own admission in each case, with less aggressiveness. Nine patients (32%) had returned to different, less stressful athletic activities. Three patients were unable to play sports because of their knee instability. The use of a brace for all athletic activities had been recommended to most of the patients initially, but only six were using a brace on a regular basis. None of the patients had found that the brace allowed them to perform in more stressful sports, but they did feel it gave them a greater sense of security regarding the knee, and in some cases, reduced the swelling and discomfort experienced with sporting activities. The six patients who wore the brace felt that it reduced the frequency of giving way. Eight of the 12 reconstructed patients had resumed sports at a modified level. Four of the 12 reconstructed patients had discontinued sports because of the instability. Ten of these 12 patients used some form of bracing. Pain was not a major complaint for most patients in this series. Thirteen patients (46%) had no complaints under any circumstances. Ten patients (36%) experienced mild discomfort associated with stressful activities, usually related to episodes of giving way. Five patients (18%) had more significant generalized knee pain, frequently occurring with daily activities. Of the 12 patients who had already come to surgery, 6 had had pain with giving way in their presurgery status, whereas the remainder had had minimal complaints of pain. Swelling of the knee was not a significant concern for most patients. Nineteen (68%) reported no swelling of the knee. Six (21%) had only occasional mild swelling, four (14%) had frequent mild swelling, and one had occasional but significant swelling. In those patients who reported intermittent swelling, the swelling was usually related to episodes of giving way. Of the 12 patients who had come to surgery, 4 had had swelling associated with giving way. Examination of the knees at followup revealed positive Lachman, anterior drawer, and pivot shift maneuvers in all patients. Nearly all patients with subjective instability identified the pivot shift as the same sensation they experienced during their giving way episodes. There were 14 patients who had Grade I medial instability with a valgus stress at 30 of flexion. That is defined as greater than 0 to 5 mm of opening compared to the opposite, normal knee. Nine patients had Grade I lateral opening with varus stress at 30 of flexion. There was no instability in full extension. None of the patients had a posterior sag or posterior draw. Almost all patients had normal measurements and configuration of thigh musculature. Unfortunately, x-ray films were obtained in only 23 of these patients. This included the preoperative radiographs in 7 of the 12 patients who had come to surgery. Thirteen of these films were interpreted as normal. In nine patients there were subtle changes of degeneration with tibial spine lipping and minimal squaring off medially and laterally of the tibial condyles. Two patients who had initial meniscal tears, one with a complete meniscectomy and the other with partial meniscectomy, had subtle degenerative changes. The radiology report indicated mild or minimal osteoarthritis in only four of the nine patients. It was the authors opinion that the remainder of these patients also had mild osteoarthritis. One patient was reported as having moderate osteoarthritis. The radiologic interpretation of these patients, particularly those that were reported as normal by the radiologist, may be somewhat subjective. There was no correlation between these changes and follow-up time, although the patient with moderate osteoarthritis was 4 years following his ligament injury. Of the 23 patients, 10 had some degenerative changes (43.4%). Overall rating An arbitrary rating system incorporating the objective and subjective results of this review was devised. An excellent knee following disruption of the ACL had no giving way, no pain, no swelling, and full return to sports. A good knee had either no giving way or only occasional giving way with stressful activities, no pain, no swelling, and return to preinjury sports with only slight limitations. A fair knee had giving way frequently with stressful activities, mild pain, occasional swelling, and prohibited return to the same sports without modification but allowed different, less stressful sports. A poor knee had giving way with daily activities, significant pain and swelling, and prohibited return to any stressful sports. Operative intervention for reconstruction of chronic anterior cruciate insufficiency was considered a criterion for fair or poor rating. Based on the above scale, there were no excellent knees, 5 (12.5%) good knees, 23 (57.5%) fair knees, and 12 (30%) poor knees. DISCUSSION Although this study has tried to avoid some of the shortcomings of previous reports, it has its own potential deficiencies. A substantial number of patients originally meeting the

4 208 criteria for inclusion into the study were lost to followup. When there are relatively small numbers of patients, minor variations can statistically affect the results. The patients lost to followup had moved and could not be traced and, therefore, theoretically represented a random sample of the entire group. We can only hope that the results of the 40 patients available for review were representative of those lost to followup. This study was not &dquo;prospective&dquo; in the true sense of the word. In fact, the criteria were developed in retrospect but nonetheless are the best we have to date approaching a &dquo;natural history study.&dquo; This, however, does not imply lack of treatment but only absence of surgery on the ligament itself. An additional shortcoming of this study is the relatively short followup (44 months). A significant concern about knees with ACL insufficiency is the possibility of eventual development of secondary osteoarthritis. The occurrence of articular changes associated with knee instability from cruciate insufficiency has been reported in both animap,9,10, 11,15,16,20 and human studies.l4~ 17 Although there is a short followup in this study, we have attempted to look at this issue. Radiographs of 23 of the patients, usually with longer followup, were obtained. Thirteen radiographs were normal. One knee had moderate changes of osteoarthritis and nine had subtle radiographic features of early osteoarthritis. Since radiographs were obtained on only a portion of the patient group, it is difficult to apply statistical significance. However, the 43.4% incidence of radiographic signs of osteoarthritis is probably not inconsistent with the 21% incidence reported by Noyes et al.l and the 78% incidence (22% marked and 56% subtle) of radiographic changes of osteoarthritis reported by McDaniel and Dameron 14 in their patients with longer followup (9.9 years from the time of the initial injury). The patients in our study were selected because of their instability. We remain suspicious that changes of secondary osteoarthritis will be slowly progressive, and longer followup may disclose an increasing incidence of arthritis in these knees. However, the role of early surgery affecting the development of arthritis is unknown. Two patients who had initial meniscal surgery had subtle changes of osteoarthritis, and it may be that early meniscal surgery, particularly in the form of excision, may predispose to later development of osteoarthritis. With such a small number in this series, it would be difficult to comment reliably. There may be some criticism of our accepting patients into this study as long as 4 weeks from their initial injury. Most of the patients presented with pain and swelling immediately following their injury. Only a small group presented within the ensuing weeks, but this fact may have skewed the results. These patients presented because of their injury, however, and not because of the complaint of &dquo;giving way.&dquo; Argument could be made over the diagnostic criteria used for patient inclusion in this study. There was no diagnostic problem in the 28 knees in which arthroscopy or arthrotomy confirmed the cruciate rupture. In the remaining 15 patients, the diagnosis was based on clinical examination alone. There is no unanimity of opinion about the clinical signs of acute isolated ACL insufficiency. Lachman, anterior drawer, and various pivot shift maneuvers can be used to elicit instability following ACL injury. It remains to be proven, however, that every knee with rupture of the ACL will demonstrate a positive test for each of those maneuvers. Fetto and Marshall demonstrated a positive pivot shift in 89% of cadaver knees following transection of the ACL, and absence of the pivot shift in every case in which the ACL was intact, even following transection of the anterolateral supporting structures of the knees. Since the pivot shift is the maneuver which most closely reproduces the pathologic movement of the unstable knee, that test was selected as the sine qua non of ACL insufficiency for this study. It is possible that various degrees of instability can occur following ACL rupture, depending on the secondary soft tissue restraints and the intrinsic stability provided by the bone architecture. Some believe loss of lateral restraints plays a vital role in the anterior cruciate deficient knee. These patients are not among those reported in this series. By selecting the pivot shift maneuver as our diagnostic sign of ACL rupture, we may be selecting out the most unstable knees. With our diagnostic criteria, knees with greater intrinsic stability may appear to have an intact ACL despite its rupture, since the pivot shift may not be present. Possibly the Lachman or anterior drawer maneuvers would be more sensitive for detecting more subtle signs of instability; however, arguments either way are conjectural since no scientific data has been reported to answer this question. A recent report9 would suggest that the presence of an ACL tear correlates with the presence of a pivot shift phenomenon. Partial cruciate ligament tears were not addressed in this report; during the study, knowledge of the partial tear with anteromedial and posterolateral band disruption was not appreciated. There was some concern about the development of Grade I lateral and medial instability in followup. The authors had carefully concluded that clinical examination revealed no lateral or medial instability at the time of injury. At the time of followup, however, there was a group of patients who had developed Grade I medial and lateral instability. It would be our interpretation that this represented a secondary stretching of other ligamentous constraints about the knee. Whether this was in the presence of microscopic collateral pathology initially remains conjectural. It should be reemphasized that collateral instability was looked for and not found at injury, or the patients would have been excluded from the study. Some patients who did not have an examination under anesthesia and arthroscopy could have had undetected medial or lateral instability at the time of initial clinical examination. Again, some authors suggest that lateral damage is part of the cruciate deficient pattern. There was an alarmingly high incidence of later ACL reconstructive procedures performed in the patients reviewed. In their report of symptomatic anterior cruciate

5 209 insufficient knees, Noyes et ai.l8 found late reconstruction necessary in 21% of their patients, while an additional 21% were considering surgery because of problems unrelieved by nonoperative management. McDaniel and Dameron 14 reported that 12% of their patients eventually had a surgical procedure to stabilize the knee. Late ACL reconstruction for persistent instability was performed in 30% of the patients in our study. The mean age of those patients eventually having a reconstructive procedure was 18 years. The mean age of the other patients was 23 years. Interpretation of this difference is difficult. It could be that more severe injuries are suffered by younger patients, or possibly they place greater physiologic demands on the knee following injury such that equivalent degrees of instability are more functionally disabling for younger patients than for relatively older patients. This factor may be activity related. The incidence of meniscal tears occurring in association with ACL insufficiency has been reported as 19% by Feagin et al.,2 42% by Giove et al., 46% by Kennedy et al., and 70% by McDaniel and Dameron. 14 Those reports have not clearly distinguished between primary meniscal tears occurring at the time of the initial ACL injury and secondary tears occurring at some later date. There was a 4 of 25 (16%) incidence of primary meniscal tears in the patients reviewed in this study. During the earlier stages of this study the authors were not as proficient with the arthroscope, using only anterior portals, so conceivably some posterior horn tears were missed. These patients are included, although they do not represent truly isolated ACL tears. An additional four patients developed secondary meniscal tears requiring surgical intervention during the follow-up period. We were confident in considering these as secondary meniscal tears since each of the affected patients had had arthroscopy at the time of the initial injury, and no meniscal pathology was found. We suspect that with longer followup an increasing incidence of secondary meniscal lesions may be found. Other patients in this series who did not come to arthroscopy may have had undetected meniscal pathology. The most common complaint among patients was giving way. McDaniel and Dameron14 reported that 70% of their patients had trouble with giving way. Fetto and Marshall4 reported 77% giving way, and Noyes et al. 17 reported 65%. We would assume that the remainder of patients in these studies were referred because of pain and swelling. We found that 86% of the patients reviewed had at least occasional episodes of giving way. Many of the patients had learned to minimize the occurrence of giving way by modifying their activities. Even though they had learned to avoid most movements precipitating the giving way episodes, they were still apprehensive about their knees and had a nearly constant feeling of insecurity. Pain and swelling in the knee were not significant problems for most of the patients. At the time of followup, 46% of the patients were without knee pain and 68% reported no episodes of swelling. For nearly all patients who were having pain and swelling, these problems were intermittent and not disabling, and generally were related to significant episodes of giving way. Successful return to stressful sporting activities was not common among our patients. Most patients were still athletically active but had been forced to modify their sporting activities. Giove et al.s and McDaniel and Dameron14 reported that 12% and 47% of their patients, respectively, were able to return to full activities without limitations following nonoperative treatment of ACL ruptures. Fourteen percent of our patients were able to resume sporting activities at their preinjury level. An additional 43% were still very active in athletics, although they had some limitations because of their knee instability. Equivalent instability may be more disabling for younger patients because of higher activity demands upon their knees. The overall results of this review present a somewhat grim prognosis following an isolated ACL rupture. By our grading system, 87.5% of the knees were rated as fair or poor. Approximately one-third of the patients required late surgery for meniscectomy, ACL reconstruction, or both. None of the patients involved in this study are currently considering reconstructive surgery, although many have significant signs and symptoms of instability. Although most of the patients subjectively believed that their knee instability was gradually becoming less troublesome for them, most reported a continuing process of activity modification which allowed them to function &dquo;around&dquo; their unstable knee. Despite the fact that many patients had learned to cope with their problem and were subjectively doing reasonably well, there was no evidence to suggest that their knees were gradually becoming more stable. In fact, with the increase in varusvalgus instability present at followup, this would suggest just the opposite. Physical examination revealed pathologic subluxation of the tibia with the various pivot shift maneuvers in every case. Unfortunately, when the study was commenced almost 8 years ago, grading of knee ligament instability, especially as it relates to the Lachman and pivot shift, was embryonic and neither well understood nor generally applied. At the initiation of this study, the Lachman and pivot shift were either present or absent. This, unfortunately, did not allow us to observe whether there was any progression of the instability based on these two parameters. At followup we did grade the pivot shift and Lachman, but since we were unable to compare it to the initial findings to get an idea regarding progression of instability, those grades have not been presented. However, varus and valgus instability, which was negative at the time of the initial diagnosis, was present at followup as Grade I instability in a significant number of patients. Whether this represents a progression of instability with loss of secondary restraints or suggests that no injury is truly isolated remains conjectural. The issue remains: Can the patient with an acute isolated ACL rupture be helped by surgical intervention, whether it be primary ligament repair or reconstruction? The orthopaedic literature is replete with optimistic reports of many different operative procedures, particularly for late recon-

6 210 struction designed to deal with this problem. Final judgment regarding these procedures must be reserved until long-term results are available. With clearer knowledge of the natural history of this injury, we are better prepared to make prognostic and therapeutic decisions for each individual patient. The prognosis of the ACL deficient knee appears poor, particularly in young active patients desirous of participating in stressful sporting activities. In the presence of meniscal pathology/meniscal surgery, osteoarthritis may be even of more concern. We can hope that as long-term followup studies become available, we will be better equipped to make more intelligent decisions regarding the appropriate treatment for this injury and that with time we will learn how to alter favorably the patient s course following this injury. REFERENCES 1 Bohr H Expenmental osteoarthntis in the rabbit knee joint Acta Orthop Scand , Feagin JA, Abbot HG, Rokous JR The isolated tear of the anterior cruciate ligament J Bone Joint Surg 54A , Fetto JF, Marshall JL Injury to the anterior cruciate ligament, producing the pivot shift sign J Bone Joint Surg 61A , Fetto JF, Marshall JL The natural history and diagnosis of anterior cruciate ligament insufficiency Clin Orthop , Franke K Clinical experience in 130 cruaate ligament reconstructions Orthop Clin North Am , Giove TP, Miller SJ, Kent BE, et al Nonoperatme treatment of the torn anterior cruciate ligament J Bone Joint Surg 65A , Kennedy JC, Weinberg HW, Wilson AS The anatomy and function of the anterior cruciate ligament J Bone Joint Surg 56A , Liljedahl S, Lindvall N, Wetterfors J: Early diagnosis and treatment of acute ruptures of the anterior cruciate ligament A clinical and arthrography study of forty-eight cases J Bone Joint Surg 47A , Lucie RS, Wiedel JD, Messner DG The acute pivot shift Clinical correlation Am J Sports Med , Marshall JL Penarticular osteophyte Clin Orthop , Marshall JL, Olsson S Instability of the knee A long-term expenmental study in dogs J Bone Joint Surg 53A , Marshall JL, Rubin RM Knee-ligament tnjunes A diagnostic and therapeutic approach Orthop Clin North Am , Marshall JL, Warrent RF, Wickiewicz TL Pnmary surgical treatment of antenor cruciate ligament lesions Am J Sports Med , McDaniel WJ, Dameron TB Untreated ruptures of the anterior cruciate ligament A follow-up study J Bone Joint Surg 62A , McDevitt CA, Muir H Biochemical changes in the cartilage of the knee in expenmental and natural osteoarthntis in the dog J Bone Joint Surg 58B , McMaster JH, Weinert CR, Scranton P: Diagnosis and management of isolated antenor cruciate ligament tears J Trauma , Noyes FR, Mooar PA, Matthews DS, et al The symptomatic antenor cruciate deficient knee The long-term functional disability in athletically active individuals J Bone Joint Surg 65A , Noyes FR, Mathews DS, Mooar PA, et al. The symptomatic anterior cruciate deficient knee The results of rehabilitation, activity modification, and counselling on functional disability J Bone Joint Surg 65A , O Donoghue DH An analysis of end results of the surgical treatment of major injuries to the ligament of the knee J Bone Joint Surg 37A. 1-13, O Donoghue DH, Frank GR, Jeter GL, et al Repair and reconstruction of the antenor cruciate ligament in dogs J Bone Joint Surg 53A , 1971