Fate of the untreated anterior cruciate ligament-injured knee

Introduction

The ideal natural history study of any specific acute knee ligament injury would identify all of the patients who sustained this injury within a population. It would document definitively the presence of this injury and exclude or subcategorize patients with additional injuries (including other ligament injuries, fractures, chondral injuries, and meniscal injuries). It would follow these patients over a long time without intervention and finally, it would assess the status of all of these patients objectively, subjectively, and functionally.

Problems noted in natural history studies of the ACL-deficient knee (1)

• •Many un documented, and undiagnosed ACL injuries
• •Patients specifically selected for nonsurgical treatment form a larger group
• •Acute and chronic injuries mixed together
• •High percentage of patients lost to follow-up
• •Patient age and activity level not accounted for
• •Frequency of associated injuries varies from group to group
• •Non-surgical treatment is variable (rehabilitation, brace, etc.)
• •No consistent method for reporting results

Meniscal or chondral damage frequently occurs at the time of the initial ACL injury. In general, approximately half of patients with acute ACL disruptions have associated meniscal tears.2, 3, 4, 5, 6, 7, 8 Many of these tears may not require surgery. The incidence of meniscal tears in the patient with an acute ACL injury is high, but the incidence of reparable meniscal injuries is low. Daniel et al.⁴ noted a higher incidence of reparable meniscal tears among patients undergoing late ACL reconstruction than among patients presenting with an acute ACL injury.

Knee function after ACL disruption

Satku et al.⁹ followed a group of ACL-injured patients for 6 years with the aim of trying to define “patients in whom current and potential disability outweighed the risks of surgery.” In these patients, rupture of the ACL was said to be their “predominant injury”, but other pathology was not specifically excluded. Satku et al.⁹ reported that 63% were able to return to pre-injury sports after injury, including four of the patients with bilateral ACL deficiency. By the time of follow-up (2–11 years, average 6 years), however, only 40 of these 55 were still able to participate in sports. Forty-two percent of the knees examined less than 5 years after injury had undergone meniscectomy, while 68% of knees examined more than 5 years after injury had undergone meniscectomy. They thus implied significant ongoing risks of meniscal injury even several years after ACL injury.

Pattee et al.¹⁰ reviewed surgical. They observed that few patients considered their instability to be severe and most coped by modifying their activities. Mild or moderate pain was reported by 61% of patients, usually relating to strenuous or prolonged exercise. Swelling occurred occasionally in 42% of patients. Thiry-three patients (67%) had partial meniscectomy at the index procedure. Only two patients underwent late meniscectomy. In a review of 107 patients with documented ACL tears undergoing arthroscopy for an acute knee injury. Drongowsky et al.¹¹ evaluated the effect of chondral and meniscus injury on patient function. The authors noted that injury to the hyaline cartilage was associated with increased symptoms of swelling and pain, and that these individuals were disabled for lighter activities (eg. Jogging) in addition to more strenuous sports. The authors were unable to demonstrate a similar effect of meniscus injury on the behavior of the ACL-deficient knees in their study. Because this retrospective sample represents a mixed patient population, it is impossible to know if the chondral injuries were, in fact, acute. If they were not, then these knees were already accumulating damage more rapidly than other knees. Recent MR imaging studies have shown that bone contusion and cartilage injury are commonly associated with an acute ACL injury.12, 13, 14, 15, 16, 17 Further follow-up is needed to ascertain what effect these lesions have on outcomes after ACL ruptured.

A few prospective studies in the literature offer the most complete picture of the outcomes to be expected after acute ACL injury.5, 18, 19, 20, 21, 22 Hawkins et al.²¹ reported on a series of 40 patients with isolated ACL injuries. The follow up picture was: “somewhat grim.” Twelve (30%) patients required late reconstruction because of “giving way.” Of the 28 patients who did not undergo ACL reconstruction, 86% experienced “giving way” and restricted their activities to minimize their symptoms. Only 10% of the patients were able to resume the same level of sports without reconstructive surgery. Hawkins et al.²¹ developed and described an “arbitrary rating system” incorporating objective and subjective factors. On this scale, there were not any “excellent” ACL injured knees; 12.5% were rated as “good,” 57.5% were rated as fair, and 30% were rated as poor.

Level	Activity	Examples
I	Jumping, Pivoting, hard cutting	Basket ball, foot ball, soccer
II	Lateral motion, less jumping or hard cutting less than level I	Basket ball, racket sports, Skiing
III	Other sports	Jogging, running, swimming

Daniel et al’s.⁵ study included a large proportion of patients performing at lower levels of sports participation. In that study, most patients did well with activities of daily living. Furthermore, no patient required a change of occupation as a result of knee instability, although many patients reported functional limitations at demanding, manual jobs. Most ACL-deficient patients were able to participate in low-risk sports activity. The number of pre-injury hours of sports participation at levels I and II³¹ was an important predictor of the success of conservative treatment.⁵ Increased participation in “high risk” sports had a strong negative correlation with success of conservative treatment. As discussed previously, earlier studies have suggested that the degree of knee laxity can be an important determinant of outcomes following ACL rupture.12, 23, 24 Eastlack et al.²⁵ reported no discernible difference in anterior laxity measured with the KT-1000 between “copers” and “noncopers” with ACL deficiency.

The symptomatic chronic ACL-deficient knee

Noyes et al.²⁶ speculated that some of the patients with pain and swelling may have had meniscal tears that had not come to meniscectomy. It is possible, though not substantiated, that meniscal tears themselves may have contributed to Fairbank changes,²⁷ making it more difficult to establish a statistically significant effect of meniscectomy. In the second paper of this series, Noyes et al.²⁸ reported the results of rehabilitation, bracing, and activity modification on 84 patients with symptomatic ACL-deficient knees. About one third of these patients improved so that they had minimal or no symptoms with activities of daily living or light recreational activities. Most of these patients still had symptoms, especially during strenuous sports. Only 9% returned to full competitive athletics. About one third of the patients were unchanged despite the program, and one-third worsened during it. Noyes et al.²⁸ could not predict which patients would improve on this program. Statistical analysis showed that those which had “giving way,” as few as two or three times per year, were at significant risk for developing arthritic changes, although they did not furnish the data which substantiated this assertion. Fowler and Regan²⁹ reported the results of meniscal arthroscopic surgery and rehabilitation in the treatment of patients with symptomatic chronic ACL insufficiency. They stressed that all of the patients were symptomatic; this paper did not attempt to define the natural history of all ACL injured patients. They excluded patients with “associated primary collateral or PCL damage

Partial ACL tears

The term “partial ACL tear” has not been clearly defined in the literature; it implies that some of the fibers are torn, whereas some remain intact. In practice, it generally means that the ligament, while exhibiting signs of injury, still spans the joint without interruption. The extent of partial ACL tears is difficult to ascertain by arthroscopy. Partial ACL tears characterize 10%–28% of all ACL tears.3, 30, 31, 32, 33, 35, 36 Umans et al.³⁵ observed that MRI could not reliably distinguish partial from complete ACL tears. Using strict criteria for describing ACL injury patterns seen on MR images, Roychowdhury et al.³⁶ compared MRI findings of partial“stable”and“unstable”tears with arthroscopic findings. The investigators could not distinguish partial “stable” injuries from arthroscopically normal ligaments, nor could they distinguish partial “unstable” injuries from complete ACL tears. The observers were able to segregate “stable” tears (normal ligaments and stable partial tears) from “unstable”tears (unstable partial tears and complete tears) with 100% sensitivity and 96% specificity. Unfortunately, they did not measure knee stability itself, but only inferred it based on the continuity of ACL fibers at arthroscopy. Reports on the outcome of partial ACL tears diagnosed by direct inspection or arthroscopy have been inconsistent.²⁵ Some authors report that patients with partial ACL tears have no significant instability.³⁷ The 1-year evaluation of the patients with pathologic motion was similar to results seen in patients with unrepaired complete ACL disruptions. Function was much better in the patients with partial tears who had normal anterior stability. Currently use the term “partial ACL tear” when a portion of the ACL appears to be intact but damaged, and anterior displacement measurements are normal (KT-1000 anterior manual maximum injured-normal difference <3 mm). Outcomes among patients in this group appear comparable to outcomes in patients with intact ligaments.

Conclusion

The ACL deficient knees are prone for later meniscal injuries and intact ACL is Chondro-protective. ACL reconstruction is thus Chondro-protective and menisco-protective in the long run. Further studies and long term follow up of active young individuals who have ACL injury and still not reconstructed for some reason may throw some light in this regard.