Patients who have a first or second degree PLC injury, with less than 5 mm of increased lateral joint opening and less than 10° of increased external tibial rotation do not require surgery for this area of the knee joint.

If they have an associated complete rupture of the ACL or PCL, then this is a separate issue that must be discussed with the surgeon. It is rare for a patient to sustain only a partial injury to the PLC without damaging other structures in the knee joint.

Patients who have a third degree PLC injury that involves only a complete rupture to the FCL (with no damage to the PMTL, popliteofibular ligament, or capsule) also usually can be successfully managed with conservative measures to be discussed.

Patients who have a third degree PLC injury that involves both the FCL and PMTL (and joint capsule) require surgical reconstruction that will be covered in Part 5 of this course.


Acute knee injuries

Patients who I see with acute injuries (that just occurred) involving the PLC and either the ACL or PCL are usually in the dislocated knee category. The preferred treatment of these injuries is to wait for 5-7 days to make sure the patient does not have a neurovascular injury and to allow swelling and pain to subside. During this time, the leg is supported in a soft-hinged full leg brace in extension with a well-padded compression dressing.

bi-valved cylinder cast

In knees with extensive damage to the PL structures and PCL, a bi-valved cylinder cast with a posterior plaster shell and posterior foam calf pad may be required to provide added stability and prevent posterior tibial subluxation, as shown in the figure (see Figure on right).

[This article was published in Noyes’ Knee Disorders: Surgery, Rehabilitation, Clinical Outcomes, Noyes FR, Barber-Westin SD (eds.), Copyright Saunders, 2009 - Noyes FR, Barber-Westin SD: Primary, double, and triple varus knee syndromes: Diagnosis, osteotomy techniques, and clinical outcomes, pages 821-895.]

Lower limb elevation, ice, and compression are important. The physical therapist begins early protected knee motion, patellar mobilization, active quadriceps function, and electrical muscle stimulation. Dislocated knees scheduled for surgery require vascular consultation and possible arteriography to exclude arterial injuries, even when intact peripheral pulses are present.

However, patients with excessive soft tissue swelling, hemorrhage, and edema are not operated on until these problems subside. This is because the operative procedure will only add to the injury by increasing soft tissue swelling, risk of infection, vascular problems, risk of knee arthrofibrosis, and skin problems. In these cases, the patient goes through physical therapy and I then perform ligament reconstructive procedures later after tissue swelling is resolved and muscle function and knee motion have been restored. In my experience, only approximately one in four dislocated knees with associated PL ruptures are candidates for acute surgical procedures.

Patients with acute knee injuries that are not in the dislocated category and in whom the damage to the PLC is minor (first or second degree) are placed into a rehabilitation program to restore normal knee motion, muscle strength, gait, and overall lower limb function. Those with second-degree injuries wear a soft tissue support brace for a few weeks, but do not require crutches. The physical therapist dictates the rehabilitation exercise program based on the tolerance of the patient – progress is made based on the patient’s ability to perform exercises and tasks without pain or swelling. As I mentioned previously, if an ACL or PCL tear is present, then reconstruction of the cruciate ligament is considered after the patient has fully recovered from the initial effects of the injury – usually at least 4-6 weeks.

Patients with third-degree PLC injuries in whom either only the FCL is ruptured or partial tears also exist to the PMTL and posterolateral capsule are placed into a special cast for 3 weeks. The cast is cut so that it can be removed to allow for range of knee motion exercises, which are done with the therapist in the 2nd week after the injury from 0-90°. The therapist must do these exercises at this time, as a valgus force is applied during flexion to protect the healing posterolateral structures. A brace is worn for 3-6 weeks and the patient uses crutches during this time period for additional protection. The goal is to allow the ligaments and soft tissues to heal sufficiently that surgery will not be required. During this time, the patient is performing safe exercises to help rebuild muscle strength. At approximately 6 weeks, the knee should have good motion and muscle strength to allow weaning of crutches and further advancement of the rehabilitation program. Again, the therapist progresses the patient through various exercises based on tolerance and ultimate patient goals for the activities they wish to resume.


Chronic knee injuries

Patients with chronic, complete injuries to the PLC that occurred many months or even years ago frequently present to our Center with severe muscle atrophy and they require several months of rehabilitation to improve their muscle strength before surgery is considered. Some patients have a severe problem when they walk, as the knee hyperextends (goes backwards) with every step. These individuals undergo a special gait retraining program, where the therapist teaches them how to talk normally and also takes them through exercises to improve the strength of all of the muscles in the leg and hip. If the patient works diligently, they can usually walk normally within 4-6 weeks.

Patients who have a bowed leg (called varus malalignment) must undergo an operation termed a high tibial osteotomy first to straighten the leg. If this is not done, any ligament reconstructive procedure (to the PCL or cruciate ligaments) has a high risk of failing due to the malalignment. This is just like replacing a tire on a car that is out of alignment – if a new tire is put on the car, but the alignment is not corrected, then the new tire will soon wear out.