Understanding Common Knee Injuries And Lower Extremity Implications In Runners

By John F. Connors, DPM, and Ana J. Sanz, DPM

To have a successful sports medicine practice, it is crucial to understand not only the foot and ankle but also the knee and hip, and the mechanism of injuries affecting these areas. Having the opportunity to treat and travel with the best runners in the world has forced me to have a stronger understanding of lower extremity biomechanics, the mechanics of running and the injuries associated with running.

The knee is the most commonly injured part of the body in runners. Most of these injuries are chronic, overuse type of injuries. Knee injuries are often caused by a failure of the involved tissues to adapt to the repetitive stress applied.

Accordingly, let us take a closer look at common injuries affecting the runner’s knee and relevant lower extremity implications, and review pertinent case studies that illustrate some of the links between knee injuries and the lower extremity.

Oftentimes, the performance of a runner is based on foot type. Basically, long distance running requires a neutral foot. Overpronated feet lead to overuse injuries/syndromes. Excessive supination results in overstress. With running, the amount of force going through the lower extremity is at least three times one’s body weight. Biomechanical imbalances are accompanied by dynamic imbalances.

Clinically, a weak vastus medialis muscle (the only medial stabilizer of the patella) is associated with patellar femoral pathology and lateral maltracking of the patella in runners.

Tight hamstrings are characteristic of long distance runners. When hamstrings become too short, they limit hip and knee extension, thereby shortening stride length. This may predispose runners to inefficient stride or injury. Appropriate stretching and strengthening of all muscles of the lower extremity provide for more efficient, biomechanically sound gait.

After performing a full lower extremity biomechanical exam, we often perform a video gait analysis to assess the running mechanics of our running patients. We use Dartfish running software with a treadmill, a flat screen TV and video cameras around the runner. We perform a full lower extremity biomechanical exam before the video gait analysis. This has proven to be very beneficial to the runner.

Indeed, our goal as sports medicine specialists is injury prevention.

What You Should Know About Patellofemoral Syndrome
Patellofemoral syndrome (PFS) is the most common overuse injury among runners. More commonly known as “runner’s knee” or chondromalacia patella, this condition occurs when a mistracking patella irritates the femoral groove where it rests on the femur.

While this condition is more common among young female distance runners, it can occur at any age in either gender.

Patients usually present with vague pain in and around the anterior knee. This pain can be diffuse or localized. Patients typically complain of patella instability, painful cracking from the patella and the knee giving way. Their pain increases when climbing stairs and hills.

Crepitus is usually present with the grind test. This test involves compressing the patella into the trochlear groove with the quadriceps relaxed and asking the patient to contract the quadriceps, actively pulling the patella proximally in the trochlear groove. This patellofemoral compression can cause discomfort. In my experience treating runners, PFS is usually due to overpronation, weakness of the vastus medialis oblique (VMO) muscle and femoral anteversion. Other causes include wide hips (high Q angle), patella alta, limb length discrepancy, improper training or worn/inadequate running shoes.

One often makes the diagnosis clinically and with a biomechanical examination. Imaging studies are of limited value except to rule out a differential diagnosis or an associated pathologic condition.

As far as treatment goes, it is very important to understand the cause of PFS. After assessing this, one can institute a treatment plan.

Again, the leading causes of PFS are overpronation, a weak VMO and femoral anteversion. One must address all three of these issues.

Custom running orthotics should control the amount of overpronation. Studies have shown that orthoses are very effective in the treatment of PFS. Physical therapy is extremely helpful in the rehabilitation plan for the patient.

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