The contralateral normal knee anterior cruciate ligament is at a similar risk of anterior cruciate ligament tear (3.0%) as the anterior cruciate ligament graft after primary anterior cruciate ligament reconstruction (3.0%).

To define the biomechanical effects of total lateral meniscectomy and of subsequent lateral meniscal allograft replacement on load transmission and distribution across the human knee, we mounted 10 fresh-frozen young human cadaveric knees on a mechanical testing system. Peak pressure and contact area profiles were determined at 0 degrees, 30 degrees, and 60 degrees of knee flexion using pressure-sensitive film and a densitometer. Load transmission profiles were determined for each knee in a sequential test order: 1) intact knee, 2) after lateral meniscectomy, 3) after implantation of size-matched meniscal allograft fixed with bone plugs, and 4) after release of the anterior and posterior horn attachments of the allograft. Total lateral meniscectomy resulted in a 45% to 50% decrease in total contact area. Allograft replacement increased total contact area by 42% to 65% as compared with total meniscectomy at all flexion angles. After release of the anterior and posterior horn attachments, contact area was identical to that after total meniscectomy. Total lateral meniscectomy resulted in a 235% to 335% increase in peak local contact pressure. Allograft replacement decreased these pressures by 55% to 65% at all flexion angles, but they remained significantly greater than those in the intact state. After release of the anterior and posterior horn attachments, contact pressures were identical to those after total meniscectomy. Compared with total meniscectomy, meniscal allograft transplantation significantly increases contact area and decreases peak local contact pressures, but any biomechanical advantages are lost without bone plug fixation of the anterior and posterior horns.

The long-term results of 25 patients treated nonoperatively with isolated posterior cruciate ligament (PCL) injuries were evaluated. Mean followup was 6.2 years (range, 2.2 to 16 years). All patients were evaluated both subjectively (questionnaire) and objectively (clinical examination, x-ray films, Cybex II dynamometer, and KT-1000 Knee Arthrometer). At followup, 80% of the patients were satisfied with their knees and 84% had returned to their previous sport (68% at the same level of performance, 16% at a decreased level of performance). Mean torque Cybex II quadriceps values for three velocities of testing (45, 90, and 180 deg/sec) in patients fully returned to sport and satisfied with their knees was greater than 100% of uninvolved quadricep; conversely, those not satisfied with their knees all had values less than 100% of uninvolved knee. The amount of knee instability as determined by the KT-1000 Arthrometer was not related to the patient's return to sport nor to knee satisfaction. We concluded that the majority of athletes with isolated PCL injuries who maintain strength in musculature return to sports without functional disability.

Fifty-four patients with anterior cruciate ligament tears that were arthroscopically reconstructed within 3 months of initial injury were prospectively evaluated. Patients with grade 3 medial collateral ligament, lateral collateral ligament, or posterior cruciate ligament tears were excluded. Eighty percent of our patients had a bone bruise present on the magnetic resonance image, with 68% in the lateral femoral condyle. Two of the latter findings--an abnormal articular cartilage signal (P = 0.02) and a thin and impacted subchondral bone (P = 0.03)--had a significant relationship with injury to the overlying articular cartilage. Meniscal tears were found in 56% of the lateral menisci and 37% of the medial menisci. A significant association was present between bone bruising on the lateral femoral condyle and the lateral tibial plateau (P = 0.02). Results of our study support the concept that the common mechanism of injury to the anterior cruciate ligament involves severe anterior subluxation with impaction of the posterior tibia on the anterior femur. Determination of the significance of bone bruising, articular cartilage injury, or meniscal tears will require a long-term followup that includes evaluation for arthritis, stability, and function. These 54 patients represent the first cohort evaluated in this ongoing prospective clinical study.