Anterior Knee Pain and Patellofemoral Arthritis

Many people with pain in the front of their knee spend months or years without a true diagnosis or treatment plan. Often they are pushed from doctor to doctor, and occasionally are even relegated to pain management. Most patients with pain in the front of the knee, or anterior knee pain, however, are active and do not want to be medicated forever. The problem with anterior knee pain is that it is a difficult diagnosis to make and there are many possibilities.

One of the problems with medicine in the era of healthcare reform and ‘big-box’ medicine is that physicians no longer perform actual physical examinations.

Usually the doctors have a quota of patients to see that day that limit a visit to 8 minutes or so and the majority of that time may be spent documenting the visit in the electronic record.

While this satisfies the government and permits payment for the visit, too often the patient remains without a diagnosis simply because no physician ‘laid hands’ on them.

Anterior knee pain can be diagnosed with a good history and good physical exam with occasional confirmation via imaging. Make sure that your doctor performs a good physical examination of the knee prior to dispensing advice or treatment.

Arthritis is the common term for damaged cartilage. Cartilage is the substance that covers both sides of a joint. A joint is a connection between two bones that allows movement. Cartilage provides both a slick and strong surface that allows the two bones to slide against each other for motion and a surface that accepts impact and protects the surface bone beneath the cartilage.

As cartilage breaks down or after it is damaged, arthritis ensues. Once there is arthritis, the surface is not as strong and is not as frictionless as it should be. Movement becomes less efficient and also painful. Patellofemoral arthritis is a problem between the cartilage surface of the underside of the patella (knee cap) and the front-side of the femur (thigh/knee).

Patients with this problem often report pain, effusions or swelling and mechanical symptoms such as popping, locking or catching in the front of the knee.

Pain is actually coming from the bone under the cartilage and the surrounding soft-tissue as cartilage itself lacks nerves. By lacking nerves, cartilage cannot itself feel pain; however, the bone underneath and the tendons, muscle and ligament around that cartilage certainly can produce pain. Arthritis is more often than not due to life itself or age-related. However, occasionally trauma or injury can cause and progress the symptoms of arthritis.

For trauma to cause arthritis the cartilage itself must fracture (break) or have an identifiable impact injury. This can happen from patella dislocations or subluxations, osteochondral defects, fractures of the knee or patella, or constant improper loading of the joint due to abnormal mechanics and alignment of the knee. Instability of the patellofemoral joint is a problem and can sometimes progress to arthritis if not identified and treatment in a timely fashion. The patellofemoral joint sustains the most load and wear during activities such as ascending or descending stairs and/or squatting. When the knee flexes (bends), this joint undergoes more and more load and deformation. Maximum contact occurs at 90-degrees of flexion, but begins at 20-degrees.

The goal of treatment is to restore normal function (if possible) and reduce pain.

Usually, nonoperative treatment is the best course of action. This usually involved physical therapy, gait analysis and correction, orthotics and bracing, medications (topical and oral) and flexibility improvements. Soft-tissue balance of the knee capsule and surrounding ligaments and tendons is very important. Generally, this balance is difficult to achieve with a home-exercise-program and formal therapy or chiropractic care is necessary. In addition, the knee functions better if the hip motion and strength is optimized; this too requires formal analysis and correction.

Another method to treat arthritis of the patellofemoral joint is through viscosupplementation. This involves injections of hyaluronic acid directly into the knee itself. This substance improves the viscosity of the joint fluid. Improved viscosity allows better resistance to compressive forces. The injection also acts as an anti-inflammatory treatment and reduces the inflammation associated with arthritis. This inflammation is a source of both pain and swelling. Also, the viscosupplementation provides supplemental nutrition to the knee cartilage; this is especially important for areas as small and as hard to reach as the patellofemoral joint. Hyaluronic viscosupplementation is an excellent treatment method for arthritis of the patellofemoral joint. 

Surgery has historically not had great results for this problem. Today there are newer technologies and better reported outcomes.

However, it should still be considered a last resort. There are procedures to restore the cartilage that involve cartilage substitutes and one’s own cartilage transferred to any significant lesions on the patella.

There are procedures to realign the patella and its tendons such that the biomechanics of the knee joint change. This typically involves actually removing the bone where the patellar tendon attaches and physically moving it over and then reattaching it with a screw. This type of surgery is done to unload the patellofemoral joint and reduce the forces across that joint.

Arthroscopy is utilized to perform what is known as ‘chondroplasty’. This is basically a procedure whereby the damaged cartilage is literally removed from the knee. This is very difficult to achieve due to the anatomy of the patella; the results have been limited and there are many times poor functional outcomes of that surgery. Also through the arthroscopy, the structures stabilizing the patella can be released to effect an offloading. This is known as a ‘lateral release’. Occasionally this procedure is accompanied with a partial resection of the patella.

Anterior knee pain is very common and very debilitating. Many patients spend years without a proper diagnosis or treatment plan. The physical examination should be thorough and supplemented with advanced imaging such as MRI or CT scan. Treatment should be nonoperative if at all possible. Surgery is possible, but functional outcomes are not guaranteed and the procedures require a great deal of technical expertise and significant rehabilitation afterward.

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