The knee is basically a hinge joint, allowing backwards and forwards motion, but it is also able to rotate slightly in on itself. The bending and straightening is controlled by the hamstring and quadriceps muscles at the back and front of the thigh bone respectively, and their size and position affects the angles the legs move at, and particularly the way that the patella (kneecap) moves. Your anatomy and the patterns of your muscle use determine many of the injuries you will suffer.
‘Runner’s knee’ used to be known as chondromalacia patellae, but is now more often referred to as patello-femoral pain (PFP). It occurs when the patella fails to move smoothly and centrally through the femoral groove at the lower end of the thigh bones. This is sometimes due to muscle imbalance or abnormal anatomy, but it can also be the result of another injury which causes you to favour one leg in some way.
You’ll either suffer a persistent ache in the kneecap, which worsens with certain exercise, or you’ll feel a sudden, stabbing pain in the knee while running, which eases off when you rest. Sitting with your knees bent prior to a race can make things worse, as can running on hills or hard surfaces.
Despite the acute pain, your joint may look normal. Your knee may swell up, but this is more often due to other knee problems, such as a bursa or Hoffa’s syndrome, in which the fatty pads around the patella become swollen. You will probably have wasted inner quadriceps muscles (the vastus medialis), knock knees (genu valgum), overpronation, flattened longitudinal arches or a twisted tibia. More women suffer from the problem than men, and it often occurs in people with jobs which involve lots of sitting with knees bent.
Your doctor may try Clarke’s test, in which they’ll pull the kneecap towards your toes while inviting you to gently straighten your knee. You’ll feel pain; they’ll feel a roughness or grating as the uneven rear surface of the patella moves through the femoral groove. The doctor will also want to look at the wear of your running shoes.
Sophisticated tests aren’t normally required. A ‘sunrise’ x-ray of the flexed knee will show if your patella is abnormal, roughened or displaced, and there is little need for scans. As many cases are the result of anatomical variations, having your running gait analysed may enable appropriate corrections to be made to alleviate the problem.
What else could it be?
While primary PFP is simply that, there may well be other influences. Disruption of the ligaments within and outside of your knee, arthritis in its many forms and ankle, shin, thigh and hip injuries may all affect knee movement and produce secondary PFP.
One factor in knee pain may be an inability to lock out the knee. Trying to do so stimulates the inner quadriceps muscles which strengthen and pull the patella straight. In most cases, little harm comes from performing this exercise, however it can make PFP worse if there is an imbalance in your quadriceps muscles and you perform knee extensions on a machine. You will therefore need to perform straight-leg exercises. Change your shoes if they have become worn, and correct any biomechanical abnormalities with orthoses or other appropriate aids.
Thankfully, steroid injections and surgery aren’t often used to treat PFP. Some physiotherapists successfully tape the patella, drawing it back towards the mid-line, and can teach you how to do this yourself. Knee supports may effectively shift your patella towards the middle, but probably at some biomechanical cost which may itself cause injury. If our maker had wanted us to use knee supports, we would have been born with them. In fact, he did and we have; we have just forgotten how to develop and use them.
Other forms of physiotherapy will ease PFP, but controlled exercises form the mainstay of treatment.
Can you run through it?/Recovery time
Within certain limits, the more you do the correct knee-strengthening exercises, the quicker your recovery will be. As for running through it, masochists will have no problem, though probably at the ultimate cost of a worn patella, potential arthritis and other injuries through favouring the limb. Treating the injury makes a lot more sense in the long run.