An intricate network of soft tissues gives your knee stability. The medial patellofemoral ligament (MPFL) is part of four major ligaments in the knee. It connects your kneecap, called the patella, to your femur, also known as your thigh bone.
However, an injury, such as a knee dislocation, can cause patellar instability and require MPFL reconstruction. Although most common among young female athletes, an MPFL injury can occur in all age groups.
What are the symptoms of an MPFL injury?
Your MPFL keeps your kneecap moving smoothly inside the groove of your femur. During a patellar dislocation, your MPFL may get torn. The symptoms of an MPFL injury or torn ligament may consist of:
- A feeling that your knee is giving away or can’t support your weight
- Stiffness, pain, or swelling in the kneecap area
- Cracking or creaking sounds with knee movement
- A locking sensation that feels like your knee is stuck after sitting for a long time
- Movement of your kneecap to the side of the joint
- A loss of range of motion
- Exterior knee tenderness
What causes an MPFL injury?
A medial patellofemoral ligament occurs when your kneecap dislocates or partially dislocates and tears the ligament located on the inside of your knee. In some cases, a weakened leg muscle or underlying knee abnormality causes a tear.
However, a torn MPFL typically happens while playing sports. The athlete’s knee may be slightly bent or straight as a tackle or force pushes the kneecap out of place. Forceful twisting, turning, or knee trauma damages the ligament.
What are the risk factors for an MPFL injury?
A study published in Orthopaedics & Traumatology: Surgery & Research finds that “traumatic patellar dislocation is most often due to trauma sustained during physical or sports activity. Two-thirds of acute patellar dislocations occur in active young patients (less than 20 years old).”
Furthermore, there are several risk factors for a torn or injured MPFL, including:
- Naturally loose ligaments, commonly found in girls and women
- Trochlear dysplasia, a deformity of the femoral trochlea
- Weak leg muscles or chronic weak knee muscles
- Presence of bony malalignments, such as valgus alignment, femoral anteversion, or tibial external rotation
- Involvement in any activities with a pivoting motion such as basketball, soccer, football, and tennis
- Previous knee dislocation or patellofemoral instability
- A connective tissue disorder, like Ehlers-Danlos syndrome hypermobility type
How is an MPFL injury diagnosed?
Doctors diagnose damage to the MPFL by reviewing your medical history and asking you how you hurt your knee. They will ask about your symptoms, including the location of your pain and when it occurs.
The doctor examines your knee by testing it for strength, range of motion, and flexibility. During the exam, you may be asked to perform an activity that causes you pain while reviewing your kneecap mobility.
A doctor may request an x-ray or magnetic resonance imaging (MRI) to view your knee joint, assess ligament health, and confirm the diagnosis. Often, a primary care doctor will refer you to an orthopedic physician for further evaluation.
How do you prevent an MPFL injury?
Exercises and protective gear can help you prevent injury to your MPFL. To reduce your risk and keep your ligaments healthy, consider:
- Strengthening your quadriceps by performing leg lifts and squats
- Building the muscles in your outer and inner thighs
- Wearing protective gear during athletic activities
- Doing hamstring curl exercises
- Stopping activity when you feel pain in your knee
- Wearing a knee brace if you’ve had a previous injury
What is the treatment for an MPFL injury?
There are surgical and nonsurgical treatment options for an MPFL injury. However, once you damage your MPFL, you’re at an increased risk of a knee dislocation happening again. Therefore, it’s not advised to ignore it. Doing so may lead to patellofemoral arthritis, which may occur after cartilage affecting the ends of the bones that meet your knee joint is damaged.
Treatment options vary based on the activity level of the patient, associated injuries, and the grade of the injury. Damage to the MPFL may be classified based on the location or type of injury, such as ruptures, sprains, avulsion fractures, and tears. Doctors may sub-classify injuries as osteochondral, ligamentous, or bony avulsion injuries.
Nonsurgical treatment
Patients without pieces of soft tissue, cartilage, or bone floating around in the knee, with no cartilage damage, or those with a connective tissue disease may qualify for nonsurgical options. Many first-time and uncomplicated injuries to the MPFL can be treated using a combination of nonsurgical treatments, such as:
- NSAIDs for inflammation, swelling, and pain
- Ice and heat for pain management
- Initial immobilization and activity modification
- Physical therapy to strengthen muscles surrounding the knee
- Functional rehabilitation and range of motion exercises
- Hip, gluteal muscle, and quadriceps strengthening exercises
- A knee brace, patella sleeve — called a J sleeve — or patellar taping
Your physical therapist will give you a list of activities to avoid and exercises to complete at home. But, it’s essential to work with your doctor to determine when it’s the right time to return to regular activity.
Surgical treatment
Doctors may recommend knee surgery for severe injuries, failure of nonsurgical methods, chronic instability, detached bone or cartilage, or recurring kneecap dislocation. Surgeons may choose to reconstruct the ligament or directly repair it. The preferred method is MPFL reconstruction surgery, but other options may include:
- MPFL repair: Typically, only first-time acute injuries are considered for an MPFL repair. This method fixes the medial patellofemoral ligament and was once a method used immediately following surgery. However, in most cases, MPFL reconstruction is the better option.
- MPFL reconstruction: A new media patellofemoral ligament is created using a graft from another ligament, like a hamstring, in the patient’s body or from a donor. This protects the joint from additional damage while stabilizing the knee.
- Lateral release and medial imbrication: This procedure creates one or two incisions near the patella to tighten or loosen ligaments on either side of the kneecap. It promotes the movement of the kneecap. Medial imbrication may also tighten the tissues on the inner side of the knee by extending the quadriceps muscles on the kneecap.
Bone realignment: For abnormal anatomy, a bone realignment, such as the Fulkerson procedure, may be used. It repositions the tibial tubercle, the secondary part of the shinbone where bones form. This process makes dislocations less likely.
What to expect with MPFL reconstruction surgery?
Before surgery, the objective is to reduce knee swelling. Doctors may prescribe a knee brace and physical therapy, such as a pre-surgery rehabilitation program. The goals of MPFL reconstruction surgery are to recover full range of motion, return to normal activities, and regain knee stability.
Your surgeon will discuss what to do and not do before the surgery. Common instructions include:
- No food or drink after midnight before your surgery
- Recommendations about any prescribed medications
- The time you should arrive at the facility
- How to report an illness or infection before the surgery
Furthermore, your doctor or anesthetist will discuss your options for pain during the surgery, which may include general or spinal anesthetic. Often, MPFL reconstruction surgery is an outpatient procedure that takes one to two hours.
What is the MPFL recovery process?
Directly after the MPFL reconstruction surgery, patients receive a brace to immobilize the knee and walk with a crutch. The brace may be worn for six weeks, after which the patient begins physical therapy.
After the surgery, you’ll need to wait 48 hours to shower, and you can’t use a jacuzzi or bathtub. Since the incisions need to stay dry, you should cover your knee with clear plastic wrap. Once the sutures are removed, you can forgo this practice.
You may receive a continuous passive motion machine (CPM) for use at home. The CPM machine helps reduce stiffness and scar tissue by moving the patellofemoral joint without using the patient’s muscles.
What is the recovery timeline?
Once patients can walk without a limp, the brace may be removed. At this point, physical therapy begins and may include tools, such as a stationary bike. Three months after the surgery, you may do advanced exercises to improve your range of motion and gain endurance.
In most cases, patients can resume playing sports and normal athletic activities roughly five to six months after MPFL reconstruction surgery. However, full recovery times may vary.
Can you drive after MPFL reconstruction surgery?
During your recovery, you can not drive. To return to driving, you must be able to straighten and bend your knee without pain, which may be four to six weeks after surgery.
How successful is MPFL reconstruction surgery?
According to research published in Current Reviews in Musculoskelet Medicine, “Modern MPFL reconstruction is a well-described operative intervention which is successful in the vast majority of chronic patellar instability patients. Excellent functional results have been reported as high as 95%, and numerous studies have documented [a] significant reduction in postoperative re-dislocation.”
How can you get more information about MPFL reconstruction?
Since kneecap dislocations may have many causes and treatment options, it’s important to discuss various procedures with an experienced surgeon and physical therapist. At Alexander Orthopaedics, our team assesses your MPFL injury diagnosis then works with you to create a plan for treatment and recovery.