Lateral Collateral, Posterolateral Ligament Injuries

Lateral Collateral, Posterolateral Ligament Injuries 2017-08-03T17:18:45+00:00

The information below was taken from our eBook, “PCL and Posterolateral Knee Ligament Injuries: Everything You Need to Know to Make the Right Treatment Decision.” For more information on this and our other eBooks, see

 There are 4 main ligaments in the knee that help keep the joint stable when we walk, run, go up and down stairs, kneel, and do any weight bearing activity. In addition, the muscles and other soft tissues in the knee joint help provide stability. While the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) are commonly torn, the posterior cruciate ligament (PCL) and lateral collateral ligament/posterolateral structures (LCL/PLS) may also be injured and cause considerable problems if left untreated.

The primary posterolateral structures consist of:

  • Lateral collateral ligament (also referred to as the fibular collateral ligament)
  • Popliteal muscle-tendon-ligament unit (including the popliteofibular ligament)
  • Posterolateral capsule


Fig. 1


These soft tissues work together to prevent 4 problems from occurring: excessive widening of the outside of the knee joint, outward (external) rotation of the tibia, knee hyperextension (bending too far backwards), and varus recurvatum (knee hyperextension and bowing outward).


Fig. 2

A patient with severe knee hyperextension from deficiency of the LCL/PLS


Fig. 3

A clinical examination test (“dial test”) on the same patient shown above. Note how far the right foot points outward; this is caused by the tibia externally rotating


What Happens When the LCL/PLS Are Damaged?


Usually, tears to the posterolateral structures occur along with tears to either the ACL or PCL. Injuries to the LCL/PLS are difficult to treat and often go undiagnosed. Once detected, the decision of whether to handle these injuries conservatively (with physical therapy) or with surgery requires an orthopaedic surgeon who has thorough knowledge of knee anatomy, the ability to perform multiple diagnostic tests, experience performing various surgical reconstruction procedures, and experience directing physical therapy after surgery. Patients present with very different situations, ranging in scope from an acute isolated PCL tear to a dislocated knee to a knee with chronic combined PCL-LCL/PLS tears and early arthritis. This is why these knee injuries frequently require care from an experienced knee specialist physician-therapist team in order to have the best potential outcome.

Dr. Frank Noyes is internationally recognized for his work in the diagnosis and treatment of injuries to the posterolateral structures. Few orthopedists have the ability to properly handle this problem, as it requires knowledge of the complex anatomy and potential variations that may exist in this area of the knee joint, the function of the major posterolateral structures, appropriate diagnostic techniques, and surgical options for reconstruction.

Dr. Noyes and his research team have published many studies on the treatment and outcome of posterolateral reconstructions. These studies have demonstrated the results of various operations used to reconstruct he posterolateral tissues, and as well, the consequences that occur when posterolateral ruptures are not surgically treated. We have also studied the causes of failure of posterolateral operations done by other surgeons to better understand the appropriate surgical methods for this region of the knee joint.

At the Noyes Knee Institute, we have unfortunately seen many patients in whom the initial injury to the PCL or LCL/PLS was not treated effectively and attempts at surgery failed to restore a stable, functional knee. This is especially true in patients with tears to multiple ligaments. For instance, if a patient tears both the ACL and LCL/PLS, but only the ACL is reconstructed, the surgery may fail. Leaving a completely deficient knee ligament alone greatly increases the failure rates of reconstructions of other ligaments.

Problems that may happen to patient who have chronic injuries to the LCL/PLS include pain and instability with squatting, kneeling, stair climbing and descending, and rising from a chair. The knee may extend too far backwards (hyperextend) or bow outward, making it painful and unstable and change the way a patient normally walks. This gait abnormality may then cause problems to the hips and back. Knee arthritis is a frequent result of these injuries if they are severe and not effectively treated. Symptoms of knee arthritis include pain and swelling with sports and then, as the damage progresses, with daily activities

Diagnosing the Problems

It is critical to diagnose all of the problems that exist in a knee that is painful and unstable. A comprehensive knee examination includes the following:

  • A thorough history of all injuries that have occurred to the knee
  • Documentation of previous medical treatment that has already been done
  • A series of tests done in the clinic to determine the function of all of the ligaments in the knee
  • Tests to determine if any meniscus tears may exist
  • Tests to determine muscle strength and function
  • Examination of the kneecap: how it moves and tracks
  • Assessment of how the patient walks
  • Determination of the alignment of the lower limb
  • X-rays
  • MRI if required

How to Treat Injuries to the LCL/PLS

The LCL/PLS may be partially or completely torn. This is why the physical examination and MRI are crucial to help the surgeon determine the condition of all of these structures in the knee joint. The decision on how to treat the problem depends on the extent of the damage and how much time has elapsed between the injury and medical examination.

Indications for Surgery:

There are basic indications for surgery for damage to the LC/PLS:

  • > 5 mm of increased lateral joint opening on the varus stress test
  • > 15 degrees increased external tibial rotation on the dial test
  • Prior failed ACL and/or PCL reconstruction in addition to the above
  • Acute injuries: bony avulsion injury of the tibial or femoral attachment of the LCL

The patient may or may not also have:

  • Varus recurvatum in the standing and supine positions
  • Hyperextension gait abnormality
  • Varus malalignment (bowed leg), where an operation called a high tibial osteotomy alone will not correct the increased lateral joint opening and external tibial rotation (known as a triple varus knee)

The indications for surgery are further verified at surgery after the patient has been placed under anesthesia with a comprehensive arthroscopic evaluation of the knee joint. The “gap test” is done by the surgeon who places a calibrated nerve hook into the lateral compartment of the knee joint and measures the amount of joint opening (space between the femur and tibia) under pressure. This test provides the final indicator that severe deficiency of the posterolateral structures exists and must be surgically corrected. Shown below are photographs taken at arthroscopy of the gap test in a knee with tears to the LCL/PLS (left) compared to a normal, uninjured knee (right)

Fig. 4



Contraindications for Surgery:

    • < 5 mm increased lateral joint opening on the varus stress test
    • < 10 degrees increased external tibial rotation on the dial test
    • Varus malalignment (bowed leg), where a high tibial osteotomy will correct the increased lateral joint opening and external tibial rotation (known as a double varus knee)
    • Varus malalignment in a patient who refuses to undergo a high tibial osteotomy
    • Previous joint infection
  • Severe muscle atrophy and/or hyperextension gait abnormality: these problems must be corrected first before surgery can be considered
  • Morbid obesity: significant weight loss must be accomplished first before surgery can be considered
  • After injury, excessive swelling, hemorrhage, and edema (dislocated knee): must wait until these problems resolve before surgery can be considered
  • The presence of severe arthritic damage in the knee
  • A patient who appears to be noncompliant with rehabilitation


Conservative Treatment

If a very small amount of damage to the LCL/PLS (first degree, tearing of some fibers, ligament intact, no instability) is detected by minor tenderness and swelling on examination, the patient may be treated without a brace or crutches and gradually return to activities based on their symptoms. Some patients have more significant tenderness and swelling on the lateral side of the knee that also represents a very small, partial tear to the LCL/PLS. These individuals may require a soft support brace for a few weeks and are progressed back to activities based on their symptoms.

If an isolated LCL/PLS injury exists in which 3-5 mm of lateral joint opening and 10 degrees of external tibial rotation are found, then the knee is immobilized in a cylinder cast to allow healing of these structures in order to avoid surgery. Crutches are used, with only a small amount of weight allowed on the leg. The patient performs quadriceps isometrics exercises every hour they are awake. After 1 week, the cast is split into 2 pieces to form a bivalved cast. This allows the therapist to remove the cast and perform range of knee motion exercises in a safe manner.

Electrical muscle stimulation is used in the clinic for quadriceps muscle retraining. The exercise program is advanced and the patient wears the bivalved cast at all times (the two pieces are held together by ace bandages) and continues using crutches for another 2-3 weeks. A support brace may then be then worn for another 3 weeks if deemed necessary by the surgeon.

In some patients who have complete LCL/PLS tears, surgery must be delayed (usually in cases of dislocated knees) and in these cases, the knee is placed in a bivalved cylinder cast. The cast is removed by the therapist frequently in the initial 4 week healing period to perform range of knee motion exercises (0-90 degrees), holding the leg with the lateral compartment closed.

Surgical Procedures

Many different surgical techniques have been described to reconstruct the LCL/PLS. The more common operations that are done today replace the LCL and (if necessary) the popliteal-muscle-tendon-ligament unit and PFL with tendon grafts. It is important to replace or repair all of the damaged structures. In addition, the posterior capsule may require repair to prevent excessive knee hyperextension.

We prefer to perform what is termed an anatomic reconstruction of the LCL. Basically, tunnels are drilled into the bones (femur and fibula) where the torn or deficient ligament normally attaches. A graft (taken either from the patient’s own tissues or a donor’s tissues) is inserted into one tunnel, threaded up through the knee, and then further advanced into the second tunnel. The placement of the tunnels is critical for the graft’s ability to survive and function to provide knee stability. The graft is secured to the patient’s bone in both tunnels using various medical grade devices such as screws, sutures, pins, or screw-suture posts.

Fig. 5



There is another procedure that may be used to reconstruct the LCL called a femoral-fibular graft reconstruction. This procedure is indicated when the LCL is torn or deficient, but the popliteus muscle-tendon-ligament unit (including the PFL) is intact. It is also a good option when multiple knee ligaments must be repaired acutely or reconstructed because it takes less time to perform than the anatomic LCL reconstruction we just described. A graft is inserted through bone tunnels in the femur and fibula and “circled” around the LCL. If required, the popliteus tendon and PFL may be sutured to the graft. The posterolateral capsule is plicated to the graft or advanced to completely restore the function of all of the PLS.


Fig. 6

LCL reconstruction: The graft is placed next to the LCL and through tunnels in the femur and fibula.
Fig. 7

Multiple sutures are placed through both arms of the graft and the slack LCL. The posterolateral capsule is plicated to the graft


If the popliteal-muscle-tendon-ligament unit and PFL are deficient, a second graft is required along with the LCL graft reconstruction. We prefer to use an Achilles tendon-bone allograft for this procedure. The bone portion of the popliteus graft is placed at the femoral insertion site, the graft is placed beneath the LCL graft, and passed in a tibial tunnel. Graft fixation is done with interference screws. The popliteus graft is sutured to the LCL graft and the posterolateral capsule is advanced or plicated. This operation restores all of the structures and is necessary after complete loss of these ligaments. The steps for the anatomic reconstruction of the popliteal-muscle-tendon-ligament unit and LCL are shown below.


Fig. 8

Anatomic LCL and posterolateral reconstruction. The LCL and popliteus tendon grafts are shown.

Fig. 9

Suture of the popliteus graft to LCL graft to restore the PFL

Fig. 10

Suture plication of the posterolateral capsule



In some knees, the LCL/PLS are intact but lax and have not been replaced by scar tissue. All tissues appear normal, except they are slightly elongated. In these cases, a simpler operation may be done to restore the normal function of the PLS. The procedure (called a proximal advancement) involves removing the bone femoral attachment site of the LCL, popliteus muscle tendon, and anterior portion of the gastrocnemius muscle tendon. Cutting bone in order to shorten, lengthen, or change its alignment is referred to as an osteotomy.


Fig. 11

LCL and posterolateral advancement procedure. The dotted line shows the site of the osteotomy

Fig. 12

The bone and attachments of the LCL, popliteus tendon, and anterior gastrocnemius tendon after osteotomy



The boney attachment is moved (advanced) and relocated in the proximal direction of the LCL, where it is fixed with a staple and screw. This procedure is frequently combined with other operative procedures (such as a cruciate ligament reconstruction or high tibial osteotomy) when the more complicated anatomic posterolateral reconstruction is not required.


Fig. 13

Fixation of the new bone attachment site of the posterolateral structures is done with a staple and screw



Postoperative Rehabilitation


The supervised program of physical therapy begins the day after surgery, regardless of the procedure performed. The entire program lasts for several months, with the majority of exercises done at home or in a fitness facility. Our highly skilled physical therapy team guides the patient through the different phases of the program, which have been developed through years of research and experience. It is crucial that the patient follow the guidelines in order to have the best possible chance for a successful outcome.

Our research studies have documented very low complication rates following posterolateral reconstructive procedures, which are in part due to the initiation of immediate knee motion and muscle strengthening exercises. The patient must be compliant with wearing a special cast for 4 weeks, followed by a brace for several months. Crutches are required for 9-12 weeks.

Our comprehensive postoperative rehabilitation program may be found by clicking here. Posterolateral Protocol

Frequently Asked Questions

A careful clinical examination provides the information required to determine if a posterolateral reconstruction is indicated. Our studies  have shown that reconstruction is warranted when this examination detects at least 5 mm of increased lateral knee compartment opening (compared to the contralateral knee) and at least 10° of increased external tibial rotation. While some knees may demonstrate increased knee recurvatum or hyperextension, this finding alone does not indicate that rupture to the posterolateral structures exists.

The indications are further verified at surgery after the patient has been placed under anesthesia, and by a comprehensive arthroscopic evaluation of the knee joint. The “gap test” is done during arthroscopy by the surgeon who places a calibrated nerve hook into the lateral compartment of the knee joint and measures the amount of joint opening under pressure. This test provides the final indicator that severe deficiency of the posterolateral structures exists and must be surgically corrected.

Knees that have an ACL or PCL rupture along with a posterolateral injury require a concurrent cruciate- posterolateral reconstruction. We have found that failure to reconstruct torn posterolateral structures at the time of ACL or PCL reconstruction may cause the cruciate graft to subsequently fail. Therefore, all ligament and soft tissue abnormalities must be surgically corrected simultaneously. Our postoperative program of rehabilitation has been designed to handle this major operation, and our studies have demonstrated that patients who comply regain normal knee motion and function.

What are the contraindications for a posterolateral reconstruction?

A posterolateral reconstruction is not required in knees that demonstrate less than 5 mm of increased lateral joint opening and less than 10° of increased external tibial rotation on clinical examination. Patients with a history of prior joint infection or who are obese (body mass index > 30) are also not candidates. In addition, patients with severe atrophy of the leg muscles, especially of the quadriceps, must undergo preoperative rehabilitation to correct this problem before consideration is given for a posterolateral reconstruction.

Patients who have a history of non-compliance with rehabilitation, or who will not complete preoperative muscle strength or gait retraining when required, are not considered candidates for this operation.

Patients that have severe arthritis and loss of lateral compartment joint space are candidates for partial or total knee replacement, and not for posterolateral reconstruction.

Patients who also have varus malalignment (bowed legs) along with posterolateral deficiency must first undergo a corrective high tibial osteotomy before consideration is given for a posterolateral reconstruction. This is due to two reasons. First, in many cases the osteotomy allows adaptive remodeling and shortening of the posterolateral soft tissues to occur and therefore, reconstruction is not required. Second, our studies have shown that lower leg malalignment must be corrected, or a posterolateral reconstruction will fail. In knees in which an osteotomy does not resolve posterolateral deficiency, an anatomic graft reconstruction may be performed a few months later after the patient has recovered from the osteotomy and normal overall lower limb alignment restored.

What are the surgical options for posterolateral injuries?

There have been many methods published in the medical literature of reconstruction techniques for torn posterolateral structures. However, only a few surgeons have conducted clinical outcome studies that provide evidence of the ability of these procedures to restore the normal function of the LCL and other soft tissues.

Our studies have shown that anatomic replacement of the LCL (done by placing a graft into the normal LCL attachment sites in the femur and fibula) is required in the majority of cases. In addition, the other posterolateral structures must be surgically addressed according to the severity of the damage which the surgeon encounters during the operation. In some knees, the popliteus muscle-tendon-ligament unit must also be reconstructed with a graft. In other knees, a suture repair of these tissues may be performed. This is usually done in patients treated for an acute knee ligament injury, in which the operation is done within a few weeks of the traumatic event.

What is the rehabilitation program after posterolateral reconstruction?

Our comprehensive postoperative rehabilitation program may be found by clicking herePosterolateral Protocol

What is the scientifically-based evidence for our recommendations?

Dr. Frank Noyes and researchers at the Noyes Knee Institute have conducted several studies on the outcome of posterolateral reconstruction. These investigations followed over 90 patients who underwent different types of operative procedures along with an ACL or PCL reconstruction. The studies were published in the American Journal of Sports Medicine.

The data from these investigations revealed:

    • All major posterolateral structures must be surgically restored in order to provide the most favorable outcome in terms of restoration of normal knee lateral and posterolateral stability.
    • Anatomic replacement of the LCL with a bone-patellar tendon-bone graft is preferred over nonanatomic reconstructive options.
  • A simple plication or advancement of the posterolateral capsule may be performed in select knees; however, the surgeon must carefully understand the indications for this procedure as it has a high failure rate if not performed under the appropriate circumstances.
  • A primary suture repair of acutely ruptured posterolateral structures is only indicated in knees where bony avulsions exist which are amendable to internal fixation.
  • Bowed legs must be treated first with a high tibial osteotomy to correct the malalignment, as failure to do so carries a high likelihood of failure of posterolateral reconstructions.
  • Associated ruptures to other knee ligaments must be surgically corrected along with the posterolateral reconstruction to restore normal kinematics to the knee joint.