Distance runners commonly encounter knee problems. These can be either traumatic or "acute" injuries that result from a single misstep or chronic injuries resulting from overuse. The latter is by far the predominant type, and these injuries can be characterized not only in terms of the precise location and quality of the pain, but also in terms of whether the injury worsens or improves at the onset of running.
Significance
Overuse injuries are a runner's chief bane, and nearly half of these injuries affect the knee. The most common overuse injury affecting this joint is patellofemoral pain syndrome, or PFPS, more commonly known as "runner's knee." PFPS generally refers to chondromalacia, a degeneration of the cartilage below the kneecap, but may also refer to other knee injuries with pain that often subsides a mile or more into a run, including patellar tendinitis and generalized knee pain.
Features
As described by Dr. Stephen M. Pribut, PFPS manifests in a number of ways, with the classic symptom being pain behind or below the kneecap. Runners often have the sensation that the knee is "cracking" or about to give way. Pain tends to worsen during uphill or downhill running, while climbing or descending stairs, and on uneven terrain. Although pain may initially subside as a run progresses, it eventually worsens throughout exercise if the condition goes untreated.
Causes
PFPS occurs when the patella deviates from its normal motion and position and rubs against the top of the femur. Causes may include biomechanical derangements, worn knee cartilage, improper or worn-out shoes, high foot arches or flat feet, tight hamstring or calf muscles, and weak quadriceps muscles. The main consideration in any overuse injury, however, is repetitive stress. Even a smooth running stride entails approximately 1,500 steps per mile and an attendant risk of injury.
Considerations
Twice as many women experience PFPS as men. Other injuries to the knee that runners commonly encounter include iliotibial band syndrome, which, as described on SportsInjuryBulletin.com, produces sharp pain on the outside of the knee that worsens on downhills but disappears immediately upon stopping in most cases. Conversely, a meniscal tear causes pain on the medial, or inner, side of the knee.
Prevention/Solution
Running on soft surfaces, increasing mileage gradually, wearing well-cushioned shoes, doing quadriceps-strengthening exercises, stretching the calves and hamstrings and not overdoing hill work are effective ways to avoid incurring PFPS in the first place. At the onset of pain, runners should cut their mileage, limit activities that involve knee flexion, avoid downhills and stairs. If pain persists, a doctor may recommend anti-inflammatory medications, and for some runners orthotic shoe inserts provide relief.
