I became obsessed with what the human knee can and cannot do when one of mine shut down after a couple of days of modest runs over a nearby hill. The technical name for my injury was patellofemoral pain syndrome, otherwise known as PFPS or anterior knee pain. It felt as though I had hammered a steak knife deep beneath my kneecap, and was giving it a good twist on each step up the stairs.
Never before had so little running led to so much rueing. I therefore set out to prove that all knees are worthless. How could a joint that works perfectly well one day make you feel like a grizzled Chelsea Pensioner the next? What’s wrong with these things?
I had my right knee X-rayed, examined and rehabbed. I spoke to an evolutionary biologist about the role of the knee on the Serengeti plain. I had my single-leg squat evaluated for valgus tendencies (I am a little knock-kneed, it turns out). I had a world-class orthopaedic surgeon (my father-in-law, conveniently) draw diagrams on napkins and bury me in research papers. I watched a surgeon complete one anterior cruciate ligament (ACL) reconstruction and two total knee replacements. I failed miserably to follow the rehab advice given to me by my physiotherapist.
It all started to make sense on the afternoon that I sat looking over the shoulder of Scott Dye, a professor of orthopaedic surgery at the University of California, as he dissected the left knee of a cadaver at a conference of physiotherapists. As I watched him demonstrate the way the donor’s meniscus (knee cartilage) slid as his femur corkscrewed, I realised that not only is the human knee actually one of the most well-built force-transference mechanisms in all creation, but that the mysteries of patellofemoral pain are in fact the knee’s gift to us.
Trauma, overuse and degeneration"There tend to be three causes of injury to the knee; namely acute trauma, overuse or degeneration," says Dr Michael Stuart, an orthopaedic surgeon specialising in knee surgery and sports medicine at the Mayo Clinic in Rochester, Minnesota. The good news is that traumatic knee injuries like ACL tears and degenerative knee problems like osteoarthritis tend to strike the knees of everyday runners at rates no higher than those of everyone else. However, half to three-quarters of all running injuries are related to overuse, and knee problems, especially PFPS, dominate overuse injuries. According to a two-year study of more than 2,000 runners completed in 2002 by the University of British Columbia, USA, for example, most running injuries treated at the centre (42 per cent) occurred at the knee, with PFPS making up 46 per cent of them. The next most common knee injuries were iliotibial band friction syndrome, meniscal injuries and patella tendinitis.
Diagnostically, PFPS produces a nagging to howling pain that can begin after a short distance of running, while "under load" (climbing stairs or squatting) or while "unloaded" for an extended period of time in the bent position (for example, sitting at your desk). PFPS struck twice as many women as men in the British Columbia study, and women under 34 more frequently than those over.
According to conventional wisdom, PFPS happens when a kneecap has pulled to the side of its track and rubbed something where it should be gliding. There are various possible causes – the runner has bad biomechanics or bad bone structure; has followed bad training advice or owns bad shoes; has weak quads or tight hamstrings. Rehabilitation advice includes a programme of rest, icing, strengthening the quads and stretching the hamstrings, as well as using motion-control running shoes and reducing the amount of hill running you do as well as your overall mileage.
But the source of knee pain is still something of a mystery. "We don’t understand the pain exactly," says Dr Robert D’Ambrosia, co-author of Prevention and Treatment of Running Injuries, who subscribes to the tight-hamstring-weak-quadriceps theory. "The knee is a hit taker," says Gary Gray, a physiotherapist who advocates a more holistic perspective on the nature of sports injury. "The runner will say, ‘My knee is killing me when I run,’ but it’s usually the result of tightness in the hip, posterior fibula or pelvis." Your knee can even hurt, says Gray, from a dud ankle on the other side of your body. "If you can’t explode off your left ankle, you can’t rotate your right femur properly, and the right knee will take the impact," he says. "Often the cause of a runner’s knee pain has nothing to do with the knee."
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