Posterolateral instability knee
A sports injury or direct trauma to the knee may cause instability on the lateral side of the knee. This is called posterolateral instability. This may lead to a feeling of giving way in sports or daily activities. Posterolateral instability is often associated with cruciate ligament injuries. On this webpage, you will find information on diagnosis, treatment and rehabilitation of posterolateral knee instability.
The knee joint consists of two articulating bones: the femur and tibia. The fibula is another bone in the lower leg. The articulating ends of the bones are covered by cartilage, to optimise knee motion. Between the bones are the medial and lateral meniscus. Stability of the knee is provoded by the cruciate ligaments and the collateral ligaments.
Posterolateral knee injuries
A sudden sidewards motion of the knee in a fall, sports injury or knee distortion, may lead to an injury of the lateral side of the knee (posterolateral knee injury). This may cause pain and giving way on the lateral side of the knee, sometimes accompanied by a hematoma on the outside of the knee. The lesion often occurs in pivoting sports (football, hockey, indoor sports). Numbness or paraesthesia of the foot may be present (temporarily) after the injury. Posterolateral injuries occur at all ages and are often accompanied by other knee injuries of the meniscus and cruciate ligament injuries. The diagnosis is made by a thorough physical examination, with sometimes additional MRI and arthroscopy of the knee.
An adequate diagnosis is essential for treatment and prognosis. Severe posterolateral knee injuries are complex knee injuries. Treatment depends on the degree of injury and timing of diagnosis after the injury.
These are injuries treated within 2 weeks after the traumatic incident. Grade 1&2 lesions are treated by a plaster in extension for 3-4 weeks. Severe grade 3 injuries need surgery. The ruptured ligaments may be repaired within this time frame. In case of severely damaged ligaments, an augmentation with donor ligaments may be performed. After 2 weeks, primary surgery is not advisable due tot the presence of severe scar tissue. Scientific research has demonstrated similar results between primary and secundary (later) posterolateral reconstructions.
The leg alignment is important in chronic injuries. A varus alignment of the leg leads to persistent instability of the knee in case of posterolateral instability. Reconstruction of the ligaments in such cases will lead to secundary stretching of the reconstruction with recurrent instability. In varus aligment, an osteotomy is the primary treatment for chronic posterolateral instability (see Case ACL and Posterolateral instability). After osteotomy, 40% of patients no longer experience instability of their knee.
In case of recurrent instability and straight or valgus (X-shape) alignment of the leg, an anatomical reconstruction of the posterolateral ligaments is indicated. In this technique (described by Prof R. LaPrade, M.D., PhD), the ligaments are reconstructed with a donor achilles tendon. These are fixed in the femur and tibia. Often, a simultaneous cruciate ligament reconstruction is performed. The Orthopaedic Center Máxima is a tertiary referral center in the Netherlands for patients with complex knee ligament injuries. RPA Janssen is an instructor on yearly international knee courses for these surgical techniques (see Biography).
After the surgery
The knee is fixed in a leg brace after the surgery, later replaced by a specific knee brace. Hospital stay is 2-3 days. The day after surgery, the physiotherapist will give you instructions for walking with two crutches. Weight bearing is limited for the first 6 weeks after surgery. Concomitant knee surgery will determine the protocol for rehabilitation. Range of motion in the knee brace will gradually increase during the first 3 months. You will receive thrombosis prophylaxis in the first 6 weeks after surgery. You may start physiotherapy with a physiotherapist of your choice after 1 week. Patients from the Netherlands are referred to my practice for knee ligament reconstructions. A standardized protocol can be downloaded for the physiotherapist (Dutch only). A referral for your physiotherapist is provided at time of hospital discharge. It is recommended to raise the operated leg a few times a day for periods of 15 minutes to limit swelling of the leg. A hematoma may occur during the first week after the operation, this is normal and will disappear within 2 weeks. The first outpatient clinic appointment is after 2-3 weeks. The skin sutures are absorbable and will disappear automatically after a few weeks.
Work and sports
Rehabilitation time after anatomic posterolateral reconstruction of the knee takes 6-12 months. You may resume an office job between 2 to 4 weeks after surgery. Heavy labor may be undertaken after 8-12 weeks. These are general guidelines: it may take shorter or longer depending on knee swelling and pain. Driving a car is not allowed if you walk on crutches. You may cycle on a home trainer after 4-6 weeks. Jogging is usually possible after 12 weeks if swelling and pain are limited. Return to pivot sports is possible after 9-12 months. Recent scientific research has demonstrated that return to sports activities is related to the knee cartilage condition as well as other possible knee injuries.
All orthopaedic treatments at our hospital are reimbursed by Dutch insurance companies.
Complications after anatomic posterolateral reconstruction may be: wound disorders, infection, thrombosis, vascular or nerve injuries and arthrofibrosis (scarring of the knee). These complications occur in 1% of patients. The posterior cruciate ligament and posterolateral ligaments are situated near important vascular and nerve structures of the leg. Knee surgeons agree internationally that this type of surgery should only be perfomed by experienced knee orthopedic surgeons in specialized knee centers. A vascular surgeon should be available in case of vascular complications. At the Máxima Medical Center, a vascular surgeon is standby for all complex knee reconstructive surgeries.
Please contact the hospital:
- if there is discharge from the wound
- if the knee becomes red and pain increases
- in case of fever >38.5º C
- if there is severe swelling and a painful calf