L.B. is a young woman who is currently rehabilitating her right knee following arthroscopic surgery one week ago. Her left knee is scheduled for the same procedure in about three weeks, assuming all goes well with the right one.
This patient has had anterior knee pain for about one year. She is an avid runner for almost 20 years who has not suffered any debilitating, long-term injuries as a result of running, other than a brief episode of Iliotibial Band Friction Syndrome ten years ago (successfully treated with appropriate exercises) and a Morton’s Neuroma in her left foot three years ago (treated surgically). L.B. had not altered or increased her running program prior to the onset of her present problem (Runner’s Knee, aka patellofemoral pain syndrome, aka chondromalacia patella). She had not changed her shoe brand or model. She had not gained any weight during the preceding months or encountered any other change that would perhaps have caused a biomechanical modification leading to her injury. In other words, there did not appear to be any “training error” that would explain the etiology of her problem.
Further investigation, however, did reveal that L.B. had in fact made an addition to her training program, but not one that was directly related to running. Last summer, in an effort to improve her leg strength, L.B. embarked on an ambitious weight-lifting program. Her routine included knee extensions, leg presses, and squats, all of which increased the compressive forces on the back side of her kneecaps. The end result: erosion and deterioration of the protective joint cartilage, exposing the underlying bone to painful pressure. Once started, this degenerative process was then accelerated by the ground-reaction forces associated with running, leading to a chronic, irreversible condition. Two separate courses of physical therapy failed to resolve her symptoms that included pain with running, on stairs, with prolonged sitting, etc. – all the hallmarks of Runner’s Knee. Surgery became necessary to “clean up” the mess, as well as to reposition her kneecap to allow it to track more appropriately, thereby more evenly distributing the compressive forces on it.
Why did this happen? Why did L.B. develop these problems when so many more people engage in weight training with no adverse affects? I believe there are several answers to these questions:
1. L.B. lifted too much, too soon (sound familiar?). Her program was much too aggressive for a novice, creating more stress on the retropatellar cartilage than could be handled safely.
2. The exercises L.B. performed (leg presses, squats, knee extensions) all placed compressive forces on the knee at angles greater than those normally encountered during running. The knee joint normally flexes to only 30° during the stance phase of gait. (It flexes to 60° during swing phase, but there is little compressive force on the patella at this point.) The quad strengthening exercises L.B. performed required as much as 90° of flexion! At angles greater than 60°, the compression on the patella is at its greatest, increasing the likelihood of breakdown.
3. L.B. had a pre-existing lateral tilt of her patella. This may have been the result of her rather tight iliotibial bands (remember her problem from 10 years ago!) that in turn could be traced to hip muscle imbalances. While she may have always had a poor patellar tracking pattern, at angles of 0-30° the consequences were negligible. But with increased compression from 30-90°.
Strengthening your quads by lifting weights may help your running performance, but if not done carefully and sensibly may cause unintended injury that can hinder your running ability. The most basic advice for novice weight lifters is the same as that given to novice runners: start slowly, increase gradually, and listen to your body!