Ligamentous Injuries

Four major ligaments keep the knee stable: anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). They can be injured in isolation or in combinations related to knee dislocations. Most ligament injuries about the knee are not urgent. However, the primary care physician must remember (1) always to look out for the potential of a multiligament knee injury and the possibility of an arterial injury and (2) always to assess the LCL, based on the significantly poorer prognosis if the diagnosis and treatment are delayed beyond 4 to 6 weeks. Early identification and surgical repair of acute LCL injuries improve patient outcomes from 50% to 90%.

Medial Collateral Ligament

The MCL is the most frequently injured ligament of the knee and often associated with concomitant ligamentous injuries; 95% are associated ACL ruptures. The MCL is the primary knee restraint to valgus loads. The MCL is tested in isolation at 30 degrees of knee flexion with a valgus load (Fig. 30-31); at 0 degrees, bony constraints contribute to stability. Valgus laxity at near or full extension implies concurrent injury to the posteromedial capsule and/or cruciate ligaments. Grade 1 injuries have pathologic laxity, indicated by increased medial joint space widening, of 1 to 4 mm; grade 2, laxity of 5 to 9 mm; and grade 3, more than 10 mm of increased laxity compared to the contralateral side.

Imaging studies should include AP and lateral radiographs looking for associated bone injury or avulsions. MR scans may be of benefit in more severe injuries to look for additional associated soft tissue injuries. Initial treatment is nonsurgical for grade 1, 2, and 3 ligament sprains. Protected weight bearing is allowed with crutches and a hinged knee brace until pain resolves medially. Unrestricted ROM is allowed and encouraged. Most patients with MCL injuries do well with conservative treatment. Occasionally, patients with grade 3 injuries who do not respond to nonoperative treatment may require surgery. Timing of return to sport or function is related to severity of injury: grade 1 injuries, usually 1 week; grade 2, 2 to 4 weeks; and grade 3, 4 to 8 weeks.

Lateral Collateral Ligament and Posterolateral Ligament Complex

When evaluating the lateral side of the knee, the physician should evaluate the function of the LCL but also the stability of the knee to posterolateral rotation. The LCL is assessed with the knee unlocked at about 20 to 30 degrees of flexion with varus stress (Fig. 30-32). The posterolateral corner is tested by externally rotating the tibia when the knee is flexed at 30 and 90 degrees. If an increased spinout to external rotation is visualized compared with the opposite knee at 30 and 90 degrees, the patient has a postero-lateral corner and PCL injury. If the knee spins out only at 30 degrees compared with the opposite side, an isolated posterolateral corner injury is present (Fig. 30-33). Imaging usually includes AP/lateral radiographs and MR image. Perhaps the simplest rule for primary care physicians is that any patient with acute varus instability (injury of LCL) should be referred to an orthopedic surgeon as soon as possible.

Treatment is based on the severity of the injury. Nonsurgi-cal treatment with protected weight bearing and protected ROM early for a few weeks is recommended for isolated grade 1 or 2 LCL; grade 1 is an opening of the lateral joint line less than 5 mm, and grade 2 is an opening of 6 to 10 mm. Progressive ROM and functional rehabilitation are initiated. Return to sports can be expected in 6 to 8 weeks. Surgical indications are recommended for isolated grade 3 LCL injuries (>10 mm gapping) and any rotator instability of the posterolateral corner. Acute surgery has more favorable outcomes, and early referral to an orthopedic surgeon is recommended.

Degenerative pattern

Traumatic pattern

Degenerative flap

Horizontal cleavage

Degenerative flap

Horizontal cleavage

Figure 30-30 Representations of meniscus pathology. Degenerative tears tend to be complex, fibrinous, and horizontal. Acute tears that are vertical in the periphery may be reparable.

Peripheral tear

Radial tear

Radial tear

Figure 30-30 Representations of meniscus pathology. Degenerative tears tend to be complex, fibrinous, and horizontal. Acute tears that are vertical in the periphery may be reparable.

Figure 30-31 Valgus stress is used to assess function of the medial collateral ligament. To best isolate the MCL, the knee is unlocked to 30 degrees of flexion when stress is applied. If the knee is still unstable in full extension, other structures (PCL, ACL, posterior capsule) have been injured.

(Courtesy Mark R Hutchinson, MD.)

Figure 30-31 Valgus stress is used to assess function of the medial collateral ligament. To best isolate the MCL, the knee is unlocked to 30 degrees of flexion when stress is applied. If the knee is still unstable in full extension, other structures (PCL, ACL, posterior capsule) have been injured.

(Courtesy Mark R Hutchinson, MD.)

Posterior Cruciate Ligament

The PCL is the primary restraint to posterior tibial translation in the knee. The most sensitive test for the PCL is the posterior drawer, which is a posterior-directed force on the knee with the knee flexed to about 90 degrees (Fig. 30-34). The PCL is usually injured secondary to a posteriorly directed force on the tibia, from a fall or potentially from a dashboard injury during a motor vehicle crash. Grading of the PCL

Figure 30-32 Varus stress is used to assess function of the lateral collateral ligament. Varus laxity noted in an acute knee injury should always be referred to an orthopedic surgeon; urgent primary repair of injured structures has a better prognosis than delayed reconstruction.

(CourtesyMark R. Hutchinson, MD.)

Figure 30-32 Varus stress is used to assess function of the lateral collateral ligament. Varus laxity noted in an acute knee injury should always be referred to an orthopedic surgeon; urgent primary repair of injured structures has a better prognosis than delayed reconstruction.

(CourtesyMark R. Hutchinson, MD.)

injury is based on the posterior drawer test and the relationship of the proximal tibia to the femoral condyles. In grade I PCL injuries, the tibial plateau is slightly anterior to the femoral condyles; in grade II, plateau and condyles sit flush at the same level; and in grade III the tibia is posterior to the level. Treatment of a PCL injury is guided by injury severity and associated ligamentous injuries (Cosgarea and Jay, 2001; Wind et al., 2004). Typically, grades I, II, and III are treated nonsurgically with bracing and functional rehabilitation, to

Figure 30-35 Lachman test is the most sensitive approach to assess anterior cruciate ligament function. The femur is stabilized (whitearrows) with the knee flexed about 15 to 20 degrees and the tibia drawn anteriorly (yellow arrow). Comparison to the opposite side and assessment of a ropelike end point are key.

Figure 30-33 Dial test is used to assess the posterior cruciate ligament (PCL) and posterolateral corner and is best done with patient prone and knees together. A, Normal examination should reveal symmetry with forced external rotation. B, If increased external rotation is identified with knee flexed 30 degrees, an injury to the posterolateral corner is identified. If asymmetry persists as knee is flexed to 90 degrees, the PCL is likely also involved. (Courtesy Mark R Hutchinson, MD.)

focus on quadriceps strengthening. PCL ruptures, unlike ACL ruptures, tend to heal, and often a grade III will heal as a grade II, and a grade II as a grade I, with appropriate bracing and protection. Mild PCL laxity is usually not symptomatic for patients. If the knee becomes unstable, however, reconstruction can be delayed.

Anterior Cruciate Ligament

The ACL is perhaps the most famous of knee ligaments because of its notoriety in twisting and cutting sports. The common presentation of an ACL injury is an athlete landing in a twisting and cutting sport, feeling a pop, and having an acute hemarthrosis within 24 hours. The most sensitive test

Figure 30-35 Lachman test is the most sensitive approach to assess anterior cruciate ligament function. The femur is stabilized (whitearrows) with the knee flexed about 15 to 20 degrees and the tibia drawn anteriorly (yellow arrow). Comparison to the opposite side and assessment of a ropelike end point are key.

for ACL rupture is a Lachman test, which is basically an anterior translation of the tibia on the femur with the knee flexed 20 to 30 degrees (Fig. 30-35). The anterior drawer test is also used but is less sensitive (Fig. 30-36). The most specific test is the "pivot shift."

Initial treatment of ACL injury focuses on rehabilitation to regain ROM and strengthen the knee. Surgical indications are based on patient's function as well as future demands (Beynnon et al., 2005). For young athletes who want to play a twisting or cutting sport more than two or three times per week, ACL reconstruction is strongly recommended. The key reason for that indication is the absolute requirement to avoid the current instability or pivoting. Recurrent wobbling or pivoting of the knee leads to an increase in stress along the meniscus, meniscal failure, meniscal degeneration, hyaline cartilage degeneration, and degenerative changes in

Figure 30-36 Anterior drawer test is less sensitive for isolating anterior cruciate ligament injuries but may assist in diagnosing associated pathology. The knee is flexed 90 degrees and the tibia drawn anteriorly.

(Courtesy of Mark Rl Hutchinson, MD.)

Figure 30-36 Anterior drawer test is less sensitive for isolating anterior cruciate ligament injuries but may assist in diagnosing associated pathology. The knee is flexed 90 degrees and the tibia drawn anteriorly.

(Courtesy of Mark Rl Hutchinson, MD.)

the knee. If the athlete is willing to give up his sport, with no complaints of instability performing activities of daily living, surgical ACL reconstruction is not always necessary.

Skeletally immature athletes pose a unique challenge because of their open growth plates. Treatment options include delay of definitive surgical reconstruction until maturity, extra-articular reconstruction, and reconstruction with soft tissue across the physis (Bates et al., 2004). Most studies have shown that children are not fully cooperative with programs that have them reduce activities until skeletal maturity. This leads to recurrent episodes of instability with associated meniscal and cartilage damage. Based on this there has been a strong trend to surgically stabilize these young athletes to reduce the risk of arthrosis at a young age.

EVIDENCE-BASED SUMMARY

• No RCTs have compared surgical and nonsurgical outcomes in reduction of future osteoarthritic change for PCL injuries (Peccin et al., 1995) (SOR: A).

• Based on two clinical trials in the 1980s and insufficient RCTs, no conclusions can be drawn about conservative versus surgical treatment of ACL ruptures in adults (Linko et al., 2005).

• Surgical stabilization should be considered for skeletally immature patients with ACL injuries because they carry a high risk of recurrent instability and subsequent injury and damage to the meniscus (Bates et al., 2004) (SOR: B).

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