Synthesis of a phenotypically abnormal type XI: type II collagen ratio by chondrocytes from canine osteoarthritic cartilage

Collagen synthesis by osteoarthritic cartilage from dogs that had undergone anterior cruciate ligament transection was measured in short-term organ cultures and chondrocyte suspension cultures. Slices of osteoarthritic cartilage from unstable knees 2, 6 or 12 weeks after anterior cruciate ligament transection converted approximately 10% of the total incorporated 14C-proline to 14C-hydroxyproline, while the value for cartilage from the contralateral knee or from knees of normal control dogs was generally less than 1%. The increase in collagen synthesis in the osteoarthritic cartilage was not related to the duration of knee instability, but was greater in grossly fibrillated cartilage than in the total pooled cartilage from the osteoarthritic joint. The collagen that was synthesized was predominantly type II, although some type XI and/or type V collagen was also synthesized. Chondrocytes isolated from osteoarthritic knee cartilage of dogs 12 weeks after anterior cruciate ligament transection showed changes in collagen synthesis similar to those seen in the cartilage organ cultures. As in the organ culture studies, type II collagen was the predominant species synthesized. When cell-associated collagen was considered, type II collagen accounted for 87+/-7% of the total collagen synthesized and retained by the osteoarthritic chondrocytes. The corresponding value for cells from the contralateral knee was 63+/-10%. Since the collagen fiber in articular cartilage is a heteropolymer of type II, type XI and type IX collagen, it is likely that the newly synthesized collagens in this model of osteoarthritis form fibers that are phenotypically different from those in normal articular cartilage.     

Intra‐articular injections of bone morphogenetic protein‐7 retard progression of existing cartilage degeneration

We investigated the effect of weekly intra‐articular injections of bone morphogenetic protein‐7 (BMP‐7) on prevention of progression of existing cartilage degeneration in an osteoarthritis model in rabbits. An anterior cruciate ligament transection (ACLT) model was used to create a progressive osteoarthritis model. BMP‐7 was intra‐articular injected weekly into the right knee and PBS into the left knee from 4 weeks after ACLT. Both sides of the knees were compared macroscopically, histologically, immunohistochemically, and by micro CT. Macroscopically, fibrillation in the femoral condyle was observed 4 weeks after ACLT. In the control knees, cartilage degeneration further progressed throughout the 12‐week period. In the BMP‐7 treated knee, osteoarthritis progression was milder than in the control knees. Histologically, safranin‐O staining was decreased in the surgical knees at 4 weeks. Obvious erosions in both medial and lateral condyles were revealed in the control knees at 12 weeks, while cartilage matrix was predominantly retained in the BMP‐7 treated knees. The macroscopic and microscopic OA score in the BMP‐7 treated knee was better than that in the control in each rabbit. Immunohistochemical analysis demonstrated that both type II collagen and BMP‐7 were more expressed in cartilage treated with BMP‐7. Micro CT analysis showed that osteophytes were smaller in the BMP‐7 treated knee compared to that of the control. Weekly intra‐articular injections of BMP‐7 inhibited progression of existing cartilage degeneration. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1502–1506, 2010     

Tibial articular cartilage wear in varus osteoarthritic knees: correlation with anterior cruciate ligament integrity and severity of deformity

Tibial articular cartilage wear was assessed intraoperatively in 100 consecutive patients with varus osteoarthritis undergoing total knee arthroplasty. Severity of deformity on radiographs, integrity of the anterior cruciate ligament (ACL) at surgery, and body mass index were recorded. Posterior half of the medial tibial plateau was more commonly involved in knees with ACL deficiency; there was predominantly anteromedial involvement with an intact ACL. Varus deformity was significantly greater in knees with a deficient ACL than with an intact ACL. Severity of deformity did not alter the wear pattern, irrespective of the ACL integrity. The functional status of ACL in an osteoarthritic knee can be corroborated with the wear pattern on the tibial plateau articular cartilage.     

The anterior cruciate ligament. A functional analysis based on postmortem studies.

In forty fresh human cadaver knees the function of the anterior cruciate ligament and of its two component parts, the posterolateral part and the anteromedial band, were studied by cutting these ligaments and others in different sequences and combinations and then manually stressing the knees. The anterior drawer sign cannot be obtained unless the anteromedial band is severed. The postolateral part and the medial collateral ligament are, respectively, the secondary and tertiary restraints limiting the anterior drawer sign. Both internal and external rotation are limited by the anterior cruciate ligament, especially when the knee is in extension. The anterior cruciate ligament also limits hyperextension.     

Anterior displacement. Its effects on instability and radiolucency in total knee replacements

One hundred sixty-nine posterior cruciate condylar knee arthroplasties were evaluated for investigation of the effect of anterior displacement on instability and interface radiolucency in total knee arthroplasty. All knees were followed for at least one year, and 37 knees were followed for at least three years. The status of the anterior cruciate ligament at surgery was first compared to the postoperative, six-month, one-year, and three-year anterior drawer sign. A correlation coefficient was computed to test for the existence of a relation between these two variables. A chi-square test for statistical significance was used to compare the overall anterior drawer results with time and the anterior drawer sign at each follow-up evaluation with pain and radiolucent zones between cement and bone. For further evaluation of the effect of anterior stability on radiolucent zones, the authors analyzed the records of all their posterior cruciate condylar total knee arthroplasties over a seven-year period (average follow-up period, 2.5 years). Anterior stability over time was independent of the status of the anterior cruciate at surgery, and the presence or absence of an anterior cruciate ligament at surgery did not affect anterior stability over time. Furthermore, cutting of the anterior cruciate did not change anterior stability over time. Anterior instability proved to be statistically less at six months than at surgery and did not become worse with time. Neither anterior instability nor the preoperative state of the anterior cruciate ligament affects pain and interface radiolucency between cement and bone.     

Articular cartilage lesions of the knee

The pathogenesis and clinical significance of articular cartilage lesions of the knee persist as topics of considerable interest among orthopedic surgeons. This study was designed to assess the association of articular cartilage degeneration with concomitant intraarticular abnormalities and to correlate the prevalence and severity of articular cartilage damage with preoperative historical and physical exam findings in patients presenting with knee pain. Twenty-six history and physical exam data points were prospectively collected from 192 patients (200 knees), consecutively undergoing arthroscopic knee surgery. During surgery, all articular cartilage lesions were recorded with respect to size, location, and character and were graded according to Oglivie-Harris et al. All concomitant knee joint abnormalities were simultaneously recorded. Of 200 knees examined arthroscopically, 12 knees revealed no demonstrable etiology for the presenting symptoms, 65 knees revealed assorted intraarticular pathology but no articular cartilage degeneration, and the remaining 123 knees revealed a total of 211 articular cartilage lesions (103 femoral, 72 patellar, 36 tibial); 7 femoral, 6 patellar and 0 tibial lesions were completely isolated (no concomitant knee joint pathology). The concomitance of femoral defects with tibial lesions was highly significant (p = 0.01). Femoral and tibial articular cartilage lesions were strikingly correlated with the presence of an unstable torn meniscus (p less than 0.001). Medial compartment articular cartilage lesions were significantly more common (p = 0.001), more closely associated with meniscal derangement, and appreciably more severe than lateral compartment lesions. In 75% of anterior cruciate ligament-deficient knees with concomitant articular cartilage degeneration, the duration from injury to surgery was greater than 9 months, and in each of these cases, a history of reinjury to the knee was elicited. From these data one can conclude that: (a) in some patients with painful knees, isolated articular cartilage lesions may be the only abnormality noted at arthroscopy; (b) unstable meniscal tears are significantly associated with destruction of articular cartilage; (c) the medial compartment is particularly susceptible to articular cartilage degeneration; and (d) in our series, anterior cruciate ligament tears were increasingly associated with articular cartilage destruction as the elapsed time from injury to arthroscopy increased.     

Posttraumatic cartilage degradation progresses following anterior cruciate ligament reconstruction: A second-look arthroscopic evaluation

BackgroundSeveral studies have demonstrated that posttraumatic knee osteoarthritis progresses even after anterior cruciate ligament reconstruction. Few reports described zone-specific cartilaginous damages after anterior cruciate ligament reconstruction. This study aimed to compare the status of articular cartilage at anterior cruciate ligament reconstruction with that at second-look arthroscopy.MethodsThis study included 20 patients (20 knees, 10 males and 10 females, mean age 22.4 years, Body mass index 24.4 kg/m²) that underwent arthroscopic anatomic double-bundle anterior cruciate ligament reconstruction and second-look arthroscopy. Mean periods from injury to reconstruction and from reconstruction to second-look arthroscopy were 3.4 and 15.3 months, respectively. Cartilage lesions were evaluated arthroscopically in the 6 articular surfaces and 40 articular subcompartments independently, and these features were graded with the International Cartilage Repair Society articular cartilage injury classification; comparisons were made between the grades at reconstruction and at second-look arthroscopy. Furthermore, clinical outcomes were assessed at reconstruction and at second-look arthroscopy, using the Lysholm knee score, Tegner activity scale, International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, side-to-side difference of the KT-2000 arthrometer, and pivot shift test.ResultsEach compartment showed a deteriorated condition at second-look arthroscopy compared with the pre-reconstruction period. A significant worsening of the articular cartilage was noted in all compartments except the lateral tibial plateau and was also observed in the central region of the medial femoral condyle and trochlea after reconstruction. However, each clinical outcome was significantly improved postoperatively.ConclusionsGood cartilage conditions were restored in most subcompartments at second-look arthroscopy. Furthermore, posttraumatic osteoarthritic changes in the patellofemoral and medial compartments progressed even in the early postoperative period, although good knee stability and clinical outcomes were obtained. Care is necessary regarding the progression of osteoarthritis and the appearance of knee symptoms in patients undergoing anterior cruciate ligament reconstruction.     

Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions

BACKGROUND: Quantifying the effects of anterior cruciate ligament deficiency on joint biomechanics is critical in order to better understand the mechanisms of joint degeneration in anterior cruciate ligament-deficient knees and to improve the surgical treatment of anterior cruciate ligament injuries. We investigated the changes in position of the in vivo tibiofemoral articular cartilage contact points in anterior cruciate ligament-deficient and intact contralateral knees with use of a newly developed dual orthogonal fluoroscopic and magnetic resonance imaging technique. METHODS: Nine patients with an anterior cruciate ligament rupture in one knee and a normal contralateral knee were recruited. Magnetic resonance images were acquired for both the intact and anterior cruciate ligament-deficient knees to construct computer knee models of the surfaces of the bone and cartilage. Each patient performed a single-leg weight-bearing lunge as images were recorded with use of a dual fluoroscopic system at full extension and at 15 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. The in vivo knee position at each flexion angle was then reproduced with use of the knee models and fluoroscopic images. The contact points were defined as the centroids of the areas of intersection of the tibial and femoral articular cartilage surfaces. RESULTS: The contact points moved not only in the anteroposterior direction but also in the mediolateral direction in both the anterior cruciate ligament-deficient and intact knees. In the anteroposterior direction, the contact points in the medial compartment of the tibia were more posterior in the anterior cruciate ligament-deficient knees than in the intact knees at full extension and 15 degrees of flexion (p < 0.05). No significant differences were observed with regard to the anteroposterior motion of the contact points in the lateral compartment of the tibia. In the mediolateral direction, there was a significant lateral shift of the contact points in the medial compartment of the tibia toward the medial tibial spine between full extension and 60 degrees of flexion (p < 0.05). The contact points in the lateral compartment of the tibia shifted laterally, away from the lateral tibial spine, at 15 degrees and 30 degrees of flexion (p < 0.05). CONCLUSIONS: In the presence of anterior cruciate ligament injury, the contact points shift both posteriorly and laterally on the surface of the tibial plateau. In the medial compartment, the contact points shift toward the medial tibial spine, a region where degeneration is observed in patients with chronic anterior cruciate ligament injuries.     

Treatment with calcitonin prevents the net loss of collagen, hyaluronan and proteoglycan aggregates from cartilage in the early stages of canine experimental osteoarthritis

OBJECTIVE: To evaluate the effect of calcitonin (CT) on the histology and biochemistry of articular cartilage from unstable operated and nonoperated knee in a canine model of experimental osteoarthritis (OA). METHODS: Eighteen dogs underwent anterior cruciate ligament transection (ACLT) of the right knee and were randomly distributed into three groups of six dogs each. From day-1 after surgery until sacrifice 84 days post-ACLT, each dog received a daily nasal spray that delivered the placebo, 100 units of CT or 400 units of CT. Histologic lesions were scored. Hyaluronan (HA) and antigenic keratan sulfate (AgKS) were quantified by enzyme-linked immunosorbent assays (ELISAs), whereas aggrecan molecules extracted under nondissociative conditions were characterized by velocity gradient centrifugation. RESULTS: All canine cruciate-deficient knees developed OA. At a daily dose of 400 units, CT had no effect on the size of osteophytes but significantly reduced the severity of cartilage histologic lesions in unstable knees. CT also enhanced the HA content as well as the size distribution and relative abundance of fast-sedimenting aggrecan aggregates in cartilage from both operated and nonoperated knees. On the other hand, in the CT-treated group, the cartilage content of AgKS increased in operated joints, but not in nonoperated joints. CONCLUSIONS: Because CT delivered as a nasal spray markedly reduced the severity of most OA changes, both at the histological and biochemical level, this form of therapy may have benefits for humans who have recently experienced a traumatic knee injury, and as well as for dogs who spontaneously rupture their ACL.     

Effects of calcitonin on subchondral trabecular bone changes and on osteoarthritic cartilage lesions after acute anterior cruciate ligament deficiency.

Because SBM may contribute to cartilage breakdown in OA, experimental OA was induced in dogs by transecting the anterior cruciate ligament of the knee and treating with either CT or a placebo. CT significantly reduced both SBM and cartilage lesions. This study supports the use of CT in the treatment of canine experimental OA. INTRODUCTION: Because subchondral bone remodeling (SBM) may contribute to cartilage breakdown in osteoarthritis (OA), we evaluated to what extend calcitonin (CT) might affect cartilage and bone changes in the early stages of canine experimental OA. MATERIALS AND METHODS: Twelve dogs underwent transection of the anterior cruciate ligament (ACLT) of the right knee. After ACLT, each animal received a daily nasal spray delivering either 400 U of CT (CT-treated group; n = 6) or a placebo (PL-treated group; n = 6). At day 84 after surgery, animals were killed, and cartilage changes were graded. BMD and volume fraction (BVF) were assessed by pQCT in different regions of interest (ROIs) of the subchondral cancellous bone of tibial plateaus (TPs).Statistics included a 2 x 2 factorial analysis with +/-CT as one factor and +/-ACLT as the other. RESULTS AND CONCLUSIONS: Nonoperated (N-OP) knees were normal in both groups. In the PL-treated group, ACLT knees all exhibited OA changes, which predominated in the medial knee compartment. Furthermore, compared with N-OP knees, the BMD and BVF of ACLT joints were both markedly reduced in medial TP but not in lateral TP. In contrast, in the CT-treated group, cartilage OA lesions of ACLT knees were significantly reduced, and there was no difference in BMD and BFV between N-OP and ACLT knees. These findings suggest that the loss of subchondral trabeculae contributes to cartilage breakdown, possibly by enhancing cartilage deformation on joint loading. By counteracting bone loss, CT reduced cartilage OA lesions, and thus, might be useful in the treatment of OA in cruciate-deficient dogs.     

Medium-Term Course of Clinical Function and Progression of Osteoarthritis after Primary Reconstruction of Anterior Cruciate Ligament: 5- to 8-Year Results

This retrospective study reveals medium-term postoperative results in anterior cruciate ligament reconstruction with a bone-tendon-bone autograft of the middle third of the patellar ligament, 5 to 8 years after surgery. A total of 44 patients with a mean age of 34.7 years was followed up for an average of 72.5 months. Objective stability of the knee was evaluated by means of Lachman, pivot shift, anterior drawer and KT-1000 arthrometer measurements. 95.5% of the knees were stable, with a side-to-side difference < 3 mm. The evaluated knee score systems showed excellent results. Mean Lysholm score amounted to 95.5 points, and with the Tegner activity score, 81.8% of the patients regained their pre-injury activity level. Using IKDC grading, 88.6% of the knees were rated normal (A) or nearly normal (B), and asked for a personal assessment of their knee function, 93.2% of the patients rated it A or B, expressing a high grade of satisfaction with the result of surgery. The postoperative course of osteoarthritis showed a deterioration on the IKDC scale in 5 knees (11.4%), 2 with grade C signs of progressive osteoarthritis. A highly significant correlation (p < 0.01) was observed for progression of osteoarthritis and laxity of reconstruction >: 2 mm in the KT-1000 measurement. Reconstruction of the anterior cruciate ligament using a bone-tendon-bone autograft of the patellar ligament leads to good medium-term results with minimal progression of osteoarthritis. Restoration of ligamentous stability of the knee is important in preventing or retarding the progression of osteoarthritis following anterior cruciate ligament injury.     

Characteristics of degeneration in an unstable knee with a coronal surface step-off

To investigate the effect of instability on the remodelling of a minor articular surface offset, we created a 0.5 mm coronal step-off of the medial femoral condyle in 12 New Zealand white rabbits and transected the anterior cruciate ligament (ACL). A control group of 12 rabbits had only ACL resection and the opposite knee was used as the non-operated control. The osteoarthritic changes at 6, 12 and 24 weeks after surgery were evaluated histologically. In addition, changes in the immunological detection of 3-B-3(-) and 7-D-4 chondroitin-6-sulphate epitopes were determined because of the previous association of such changes with repair of cartilage and early osteoarthritis. In the instability/step-off group there was rapidly progressing focal degeneration of cartilage on the high side of the defect, not seen in previous step-off studies in stable knees. The rest of the femoral condyles and the tibial plateaux of the instability/step-off group had moderate osteoarthritis similar to that of the instability group. 3-B-3(-) was detectable in the early and the intermediate stages of osteoarthritis but no staining was seen in the severely damaged cartilage zones. Immunoreactivity with 7-D-4 increased as degeneration progressed.     

Electromyographic study of the anterior cruciate ligament-hamstrings synergy during isometric knee extension

The purpose of this investigation was to determine the role the hamstrings group may play in augmenting passive articular mechanisms during activity in which anterior drawer force may detrimentally affect the anterior cruciate ligament (ACL). Nine male subjects performed non-weight-bearing isometric knee extension at 10% increments of maximum voluntary contraction (MVC). Electromyographic (EMG) signals were detected and recorded from the vastus lateralis, vastus medialis oblique, vastus medialis longus, and the long head of the biceps femoris. The EMG signals were rectified and integrated over 1000 ms and normalized to subject-specific values. The data were subjected to a repeated-measures analysis of variance. The results demonstrated that expected significant increases in quadriceps excitation accompanied increases in knee extensor torque. Hamstrings excitation was not found to change significantly (total change = 3.4%). It was concluded that functionally adequate knees do not require posterior drawer force in excess of that provided passively by articular structures.     

Intraarticular sodium hyaluronate injections in the Pond-Nuki experimental model of osteoarthritis in dogs. II. Morphological findings

The effect of the intraarticular sodium hyaluronate (HA) injection on the osteoarthritic knee joint has been evaluated in dogs using an experimental model of osteoarthritis induced by sectioning the anterior cruciate ligament. Seven weeks after surgery, the damage, graded according to Mankin's scale, was significantly reduced in knee joints treated with HA from the second week postsurgery compared to untreated joints. When intraarticular HA therapy was initiated after the seventh week, osteoarthritis progression was still reduced compared to controls. Both morphology and morphometry showed a beneficial effect of HA on the cartilage response to the damage, as well as a clearcut inhibitory effect on the development of the fibroblastlike cell layer on the articular cartilage in untreated joints. The beneficial effects on the cartilage integrity and response to osteoarthritic damage might be related to a primary effect of HA on the cartilage surface. However, these effects do not exclude the possibility that, in addition, HA might act on the synovial membrane by limiting the synovial reaction.     

Proteoglycan alterations during developing experimental osteoarthritis in a novel hip joint model

Degenerative hip joint disease was induced in dogs by extra-articular surgery that created a condition that mimics hip dysplasia. Decreased acetabular coverage of the femoral head gave altered mechanical load, with ensuing cartilage degeneration. For comparison, degenerative knee joint disease was induced in other dogs by transection of the anterior cruciate ligament of the knee. The femoral head articular cartilage showed macroscopic signs of degeneration within a month. No macroscopical changes of synovitis were present. Chemical analysis of cartilage samples showed loss of proteoglycans. Guanidine hydrochloride extracts of the cartilage contained proteoglycan fragments that could be separated by equilibrium density gradient centrifugation in cesium chloride. The data indicate that proteoglycans are fragmented by proteolytic cleavage and lost from the cartilage. The proteoglycans remaining in the tissue are smaller and have lost the ability to aggregate with hyaluronic acid. Similarly, in experimental knee joint osteoarthritis, the proteoglycan content of the cartilage decreased. The structural changes of those proteoglycans remaining were of a different nature, with no changes in proteoglycan size or aggregation properties, possibly indicating that both degradation and repair took place in the knee articular cartilage and/or that fragments were rapidly lost from the tissue. This may follow from different surgical procedures, only the one used for the hip joint being extra-articular, or from the different anatomy and physiology of the hip joint and the knee joint.     

The effect of immobilization on goat knees following reconstruction of the anterior cruciate ligament

Significant patellofemoral chondromalacia was observed three months after operations on goat knees that had an excised anterior cruciate ligament (ACL) replaced and then were immobilized for six weeks with a rigid external pin and frame fixator. To determine if the patellofemoral morbidity rate could be reduced, another group of goats was treated with the same operation but without immobilization. The legs of the animals in the immobilized group had muscle weakness and the animals only occasionally used their legs for the next three to four weeks. The animals in the mobilized group protected the leg for only one to two days after surgery, and by ten to 12 days were actively moving the knee. Severe patellofemoral articular cartilage erosions occurred in the immobilized goats but not in the mobilized group. Postoperative immobilization was detrimental to the joint function and to a successful ACL reconstruction.     

Extraarticular repair of the unstable knee. Disappointing 6-year results of the Slocum and Ellison operations

Thirty-nine clinically unstable knees caused by anterior cruciate ligament rupture were evaluated 5-8 years after medial and lateral extraarticular stabilization according to Slocum and Ellison. At the follow-up, 10 knees had been subjected to an intraarticular anterior cruciate ligament reconstruction, and one knee was not available for follow-up. The mean Lysholm score for the 28 reexamined knees was 84 out of a maximum of 100 points. Activity scores were generally low, and all the knees had increased anterior drawer instability. The combination of the pes anserinus and lateral extraarticular repair did not give acceptable long-term results.     

Total knee arthroplasty with retention of both cruciate ligaments. A nine to eleven-year follow-up study.

BACKGROUND: Although many early designs of total knee arthroplasty allowed the retention of both cruciate ligaments, in most current designs of knee replacement systems, either both cruciate ligaments are removed or the posterior cruciate ligament alone is retained. This report is a review of a series of total knee arthroplasties in which both cruciate ligaments were retained. METHODS: The results of 163 total knee arthroplasties (130 patients) in which both cruciate ligaments were retained were assessed prospectively. One hundred and seven knees (eighty-nine patients) were followed for an average of ten years. There were thirty-four men and ninety-six women, and the average age at the time of the index arthroplasty was sixty-seven years (range, forty-two to eighty-four years). The diagnosis was osteoarthritis in 122 (75 percent) of the knees and rheumatoid arthritis in forty-one (25 percent). Twenty-six knees had a valgus deformity, 109 had a varus deformity, and twenty-eight had a normal alignment of 5 to 10 degrees of valgus. The anterior cruciate ligament was relatively normal in ninety-six knees and was partly degenerated in sixty-seven knees. With use of the rating system of the Knee Society, all 163 knees were prospectively evaluated at yearly intervals; fifty-six of these knees (in forty-one patients) were followed in this manner until the patient died or was lost to follow-up. RESULTS: One hundred and four (97 percent) of the 107 knees available for study at an average of ten years had an excellent or good result. At the time of the latest follow-up, pain was adequately relieved in ninety-seven knees (91 percent) and the average range of flexion was 107+/-12.6 degrees (range, 65 to 135 degrees). Ninety-five knees (89 percent) had normal anteroposterior stability (less than five millimeters of movement in this plane), and twelve knees (11 percent) had five to ten millimeters of movement as demonstrated by the drawer sign. Ninety-six knees (90 percent) had normal mediolateral stability, and eleven (10 percent) had 5 to 10 degrees of laxity. Ninety-four knees (88 percent) had valgus alignment of 5 to 10 degrees. The average knee score was 91+/-8.4 points (range, 54 to 100 points), and the average functional score was 82+/-21 (range, 10 to 100 points). The survival rate at ten years, with revision as the end point, was 95+/-2.0 percent. Seven (4 percent) of the 163 knees in this series were revised. There were no revisions for patellar problems or aseptic loosening of the tibial component. CONCLUSIONS: The good anteroposterior stability in this series after an average follow-up period of ten years indicates that both the anterior and the posterior cruciate ligaments, even when partly degenerated, remain functional when they are preserved in a total knee arthroplasty.     

Partial rupture of the anterior cruciate ligament. Natural course

A prospective study was done of 29 patients with conservatively treated partial ruptures of the anterior cruciate ligament that were stable at the initial examination under anesthesia. The ruptures were reevaluated for stability and knee function from 12 to 60 months after injury. Many had developed signs of instability. The forward drawer sign (Lachman test) and the pivot shift tests were positive. There was also measurable sagittal instability (anterior drawer sign). In every case, knee function was almost completely restored.