Knee osteoarthritis, or arthritis, is the wearing away of the protective cartilage surface covering the ends of the bones at the knee joint. When functioning properly, this cartilage allows smooth and painless motion. As the cartilage wears over time or after injury, the Patellofemoral osteoarthritis is degeneration, or wearing out, of the cartilage on the underside of the patella (kneecap) and the trochlea (groove) of the femur (thigh bone). Injury or degeneration of this cartilage can lead to arthritis, resulting in pain, stiffness, and swelling of the knee.
What Is Patellofemoral Osteoarthritis?
The patella (kneecap) is a bone on the front of the knee within the tendon of the quadriceps muscle. It rides in a groove, called the trochlea, of the femur (thigh bone).
A protective layer of cartilage on the surface of the patella and trochlea allows smooth, painless movement of the patella along the groove. Patellofemoral osteoarthritis occurs as this cartilage degenerates or wears out.
Causes and Risk Factors
Patellofemoral osteoarthritis commonly occurs with aging, although it may also occur following trauma such as a patella dislocation or fracture.
Other causes and risk factors may include:
- Injury to the cartilage from a patella fracture, patella dislocation, other trauma, or overuse
- Mechanical abnormalities or poor patella tracking associated with extreme leg malalignment
- Previous knee surgery, including surgery to realign the patella
- Obesity
- Chronic instability
- A high-riding patella or poor patella tracking
- Overuse in sports involving running, jumping, or squatting
- Poor knee alignment
- A poorly formed trochlea
- Previous cartilage injury
Symptoms
Symptoms may include:
- Pain, usually in the front of the knee or behind the kneecap
- Pain that worsens with prolonged sitting or when getting up from a seated position
- Pain when going up or down stairs or hills
- Pain with kneeling, squatting, or wearing shoes with heels
- Pain with jumping
- Achy pain that may sometimes be sharp
- Giving way or catching of the knee
- Swelling, often after activity
- Knee stiffness
Treatment
Conservative treatment may include activity modification, physical therapy, medications, and injections.
- Activity modification: It is important to continue using and moving an arthritic knee while avoiding overuse. Keeping activity below the level that causes pain and aggravation can help improve symptoms and prolong the ability to use the knee. Activities that place greater stress on the patellofemoral joint, such as jumping, running, lunges, and stairs, may need to be reduced.
- Physical therapy: Physical therapy can help patients learn how to maintain knee range of motion, strength, and function.
- Non-impact activities: Biking, swimming, and water exercises are excellent choices for cardiovascular and strengthening exercise.
- Weight loss: Weight loss can help reduce arthritic knee symptoms by reducing weightbearing forces across the knee joint.
- Assistive devices: Some patients may require a cane or walker as arthritis becomes more severe.
- Medications: Tylenol® or over-the-counter anti-inflammatory medications such as Aleve®, ibuprofen, or Motrin® can be effective for managing arthritic pain symptoms when taken appropriately.
- Injections: Corticosteroid injections deliver anti-inflammatory medication directly into the knee joint and may provide significant relief for some patients.
- Biologic injections: Platelet-rich plasma (PRP), stem cell, and amniotic fluid injections cannot repair or restore cartilage.
- Cold: Cold can be used to relieve pain and reduce inflammation. It may be applied for 15 to 20 minutes every two to three hours for inflammation and pain and immediately after activity that aggravates symptoms. A cloth should be placed between the ice and skin.
- Heat: Heat may be used before stretching and strengthening activities prescribed by a physician or physical therapist.
Surgery is considered a last resort when conservative treatment options have failed to provide pain relief and the patient continues to experience constant pain and functional limitations.
Surgical options may include:
- Arthroscopy: Arthroscopy can debride, or clean up, loose ends of torn cartilage and treat focal, small and limited breaks in the cartilage surface. Outcomes for widespread cartilage damage from arthritis are less predictable.
- Patellofemoral realignment surgery: This may be considered as a surgical option for severe symptoms.
- Unicompartmental replacement (patellofemoral arthroplasty): A single-compartment knee replacement can resurface the damaged and arthritic joint surfaces of one knee compartment when the others remain in good condition. The advantage is less surgery, but the replacement may eventually require revision to a total knee replacement. Robotic and computer navigation are improving the ability to accurately position unicompartmental implants and theoretically improve survivorship.
- Total knee arthroplasty (TKA): Total knee replacement replaces the damaged and arthritic joint surfaces with special metal and plastic while maintaining the remaining bone, tendons, and ligaments.
Recovery and Outcomes
Patellofemoral arthritis is a progressive condition that continues to worsen over time. Most conservative treatments are aimed at slowing the degenerative process and limiting symptoms.
Conservative treatment, including physical therapy and activity modification, can provide relief and allow patients to return to most normal activities.
Results and outcomes for unicompartmental knee replacement are approaching those of total knee arthroplasty. Total knee replacement has very successful outcomes regarding pain relief and achieving functional motion.
When to See Dr. Chudik
Contact Dr. Chudik’s office if symptoms worsen or if knee pain and functional limitations continue despite conservative treatment. Call 630-324-0402, email contactus@chudikmd.com or request an appointment online.