What causes the pain in “Anterior Knee Pain”?

Patellofemoral joint pain occurs when the patella, which is triangular on the back side, is not positioned properly in the groove that the thigh bone makes for it. As a result, the normal back-and-forth motion of the kneecap in this groove is impaired. Often, side-to-side patellar motion, excess patellar tilt, or excessive motion of the femur underneath the patella itself results in areas of excess bone-to-bone pressure, accompanied by pain.

Once the patellofemoral joint becomes irritated, activities that result in relatively greater quadriceps (thigh) muscle contraction will cause pain, since when the quadriceps contract the patella is pulled in toward the joint. Activities that are typically painful in patients suffering from patellofemoral pain include running, jumping, deep knee landings, descending stairs or getting up from a sitting position without the use of arms.

What brings on the condition?

There are numerous things that can result in abnormal motion at the patellofemoral joint. Some of the most common include:

• Thigh muscles that are weak on the inside (medial side) relative to the outside (lateral side). The quadriceps, which is really a combined group of four muscles (with a common attachment to the patella at the quadriceps tendon), commonly will develop relative weakness of the medial muscle or VMO. When patients develop VMO weakness, there is a relatively greater pull to the outside as the lateral portion of the quadriceps overcomes the weaker medial side. This results in a patella that is pulled to the lateral side of its groove, which can ultimately cause pain.
• Patients who pronate (have sagging arches) when they walk or run with often develop anterior knee pain because when the arch drops with each step, the tibia (shin bone) rotates excessively to compensate. This rotation also affects the patellofemoral joint and ultimately draws the kneecap laterally out of the joint as well.
• Patients with excessive hip and thigh muscle weakness often have difficulty maintaining their femur (thigh bone) in its proper position when walking or running. When these muscles aren’t functioning properly, the end result is a femur that will over-rotate, and again, the patellofemoral joint is affected.
• Patients with excessively tight muscles around the knee will sometimes develop patellofemoral pain because of the abnormal pull of the tight muscles.
• Patients with leg length imbalances can easily develop anterior knee pain due to the biomechanical problems that arise from attempts to compensate for the leg length imbalance.

How is anterior knee pain diagnosed?

It’s fairly easy to diagnose pain coming from the patellofemoral joint. In fact, patellofemoral joint pain is the most common cause of knee pain without injury in young people. Quick examination often will confirm a painful joint. The exam can also be used to rule out other problems with similar symptoms such as a kneecap that is unstable in the patellofemoral joint, a synovial plica (thickened, inflamed joint capsule at the patellofemoral joint that gets caught between the patella and femur when the knee is bent) or abnormalities of the joint surface itself.

How is anterior knee pain best treated?

Because there are so many different potential causes of anterior knee pain, individualized treatment based on a careful assessment of a patient’s biomechanics and attention to the way that the knee is being used is essential. Treating the problem at its source (i.e. hip weakness versus falling arches) increases the likelihood that the problem will stay away once it is brought under control, and should allow patients to resume and maintain a high level of activity. Thus, in addition to quadriceps strengthening exercises, it is common when treating anterior knee pain to focus on areas that are away from the knee itself.

If the pain is disabling at presentation, a short course of anit0inflammatory medication is often utilized to reduce painful joint inflammation at the joint. Anti-inflammatories should almost never be used as the sole treatment for this problem though, since they do nothing to address the issues that brought the patient to the doctor in the first place. Instead, the goal of the medication is to reduce pain to the point that effective therapy can begin.

It’s common for patients with anterior knee pain to experience periodic flare-ups, but consistency with the prescribed rehab program will usually minimize this.

Are knee braces necessary for this problem?

In instances where there is excessive tilt to the kneecap (so that the contact pressure at the outside portion of the joint is being increased) a simple neoprene knee sleeve may be helpful in the short-term to maintain the kneecap in a more normal position while strengthening exercises are started. If instability is felt to keep the kneecap from sliding out of its joint. Otherwise, braces are generally of little benefit in patients with anterior knee pain.

Am I going to need surgery for this problem?

Almost certainly not. Only a fraction of patients who present with anterior knee pain ultimately require surgery, which is a good thing, because the surgical options currently used to treat this problem carry at best, mixed results.

Will continuing to play sports with anterior knee pain injure them further?

Probably not, although if you are continuing to worsen while maintaining a given level of activity, then an adjustment should be made to help your doctor get ahead of the problem. This may involve nothing more than a simple modification of practice sessions or may involve rest from the offending activity for a period of time.

More questions? Call Stadia Sports Medicine at 515-221-1102 for more information or to schedule an appointment.