Osteoarthritis

Osteoarthritis is the wearing down of joint cartilage – the smooth layer that cushions the ends of the bones in a joint and lets them glide. When it becomes thinner and rougher, the bones rub against each other more: the joint hurts, is stiff in the morning and gets worse under strain. The joints most often affected are the knees, hips, fingers and spine. According to the Robert Koch Institute (RKI), Germany's public health agency, almost one in five adults in Germany reports having osteoarthritis – and significantly more from the age of 65.

Weight plays a big role, especially for the knees. When you walk, a force several times your body weight acts on the knee joint – and even more when you climb stairs. In a well-known study (Messier 2005), every kilo of body weight corresponded to around four kilos of load on the knee with each step. So ten extra kilos on the scales means around 40 kilos more pressure with every step – over many millions of steps across the years. On top of that, fatty tissue releases inflammatory messengers that attack the cartilage as well. That's why, in people with severe excess weight, osteoarthritis is also more common in the finger joints, which don't bear any weight at all.

The reverse is just as true: every kilo you lose takes around four kilos of load off your knee with each step. In studies, people with knee osteoarthritis reported significantly less pain and better mobility after losing just 5 to 10% of their weight – with the best results when weight loss and exercise went hand in hand.

Exercise isn't a danger here – it's the most important treatment. Cartilage has no blood vessels and gets its nutrients from the joint fluid mainly through alternating loading and unloading – like a sponge that is squeezed out and then soaks itself full again. Joint-friendly activities include cycling, swimming, aqua aerobics, brisk walking and strength training for the muscles around the joint; strong thigh muscles act like a shock absorber for the knee.

If a joint hurts for weeks, swells up or locks, get it checked by your GP or an orthopaedic specialist. Children and teenagers don't normally get osteoarthritis. If a child's joint pain lasts for days, the joint is swollen or red, or the child is limping, the paediatrician is the right place to go. Typical “growing pains”, on the other hand, usually occur in the evening or at night in both legs, not in the joint, and are gone again by morning.