Anatomy of the Knee

The knee is one of the largest and strongest joints in the human body. Vital for multi-directional movement, the knee connects the thigh-bone (the femur) to the leg bone (the tibia). Most of this connecting mechanism is accomplished through ligaments.

Description of Ligament Knee Injuries

Ligaments are made up of strong, dense connective tissue and are crucial to maintaining knee stability. They are what allow the knee to perform movements such as walking, bending, running, turning, pivoting, etc. There are four main ligaments that stabilize the knee:

The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL): These ligaments are located on the inside of the knee and form an “X” in order to prevent the knee joint from sliding back and forth (up and down).

The medial collateral ligament (MCL) and the lateral (fibular) collateral ligament (FCL or LCL): These ligaments are located on the sides of the knee and prevent the joint from moving side-to-side.

Knee ligament injuries that involve a ligament tear are very common, especially among athletes. Soccer, football, basketball, skiing and gymnastics produce the most knee ligament injuries. While most ligament injuries involve a single ligament, such as an ACL tear or MCL tear, when a major force or trauma is placed on the knee, multiple ligaments can be affected. For example, motor vehicle accidents, a hard crash on snow skis or a severe tackle on the football field can all result in complex knee injuries.

When multiple ligaments of the knee are injured, oftentimes, other problems are occurring such as a dislocated knee or a fracture. Special attention will be needed by an orthopaedic surgeon to surgically reconstruct the tears of the various ligaments.

Treatment for Multi-Ligament Knee Injuries

A careful clinical exam and the use of stress x-rays are very useful, especially when there is a chronic injury or in the case of traumatic knee injuries, where it is difficult to determine whether a side-to-side laxity is due to a medial or posterolateral corner injury. In these injuries, a patient’s alignment must be assessed, especially for chronic injuries, and a high quality MRI scan should be obtained to look for any concurrent cartilage or meniscus injuries.

Non-operative treatment may be suggested initially when there is a concurrent ACL and medial sided knee injury to allow the MCL to attempt to heal first, or if there is a concurrent grade I or grade II injury of the medial or lateral side structures of the knee with a cruciate ligament injury. When there is more than this amount of instability present in the knee, Dr. LaPrade will usually recommend a concurrent multiple ligament reconstruction. The basic principles followed for multi-ligament knee injuries are to attempt a secure and well-positioned anatomic reconstructive procedure, whereby one can start early range of motion to minimize the chance of the patient developing stiffness and scaring around the knee. We believe this ultimately leads to decreased function and osteoarthritis and our goal is to help patients return to their highest level of functioning.


As mentioned previously, it is essential to have a concurrent well-guided physical therapy program following a multi-ligament knee injury reconstruction. Patients must achieve full knee extension as soon as possible, and work on quadriceps activation and edema control. It is also important to obtain 0-90° of knee flexion within the first two weeks. Further motion is obtained between weeks two and six and patients are usually kept non-weight bearing for the first six weeks postoperatively.

Recovery after complex knee injuries require 9-12 months of postoperative rehabilitation before returning to full activities. Allowing the ligaments to heal properly and to restrict the patient from returning to activities too soon will decrease the risk of having the reconstructed graft fail or develop fatigue and endurance problems and have the operative knee or the contralateral opposite healthy knee (re)injured.

Related Studies

  • Effects of Grade III PLC Injuries on ACL Grafts
  • Effects of PLC injuries on PCL Grafts
  • Effect of Tibial Postioning on the Diagnosis of PLC Rotatory Instability in the PCL Deficent Knee
  • sMCL – Anatomic Augmented Repair vs Anatomic Reconstuction
  • Biomechanical Comparison of Anatomical Single and Double Bundle ACL Reconstruction
  • Double Bundle PCL Technique and Outcomes
  • Outcomes and Surgical Technique of Acute Grade III and Combine PLC Injuries
  • Varus Stress Radiographs
  • Correlation of Valgus Stress Radiographs
  • Kneeling Stress Radiographs for Evaluation of Posterior Knee