Your knee is one of the most powerful joints in the body. It powers jumping, running and standing up. Even though it's so powerful, it is also fairly fragile and its health depends on a balance between the quadricep muscles of the thigh, the hamstrings, the calves and the anterior tibialis on the front of the shin. If one of the muscles is too strong relative to the other muscle groups, the imbalance can put excess strain on the knee tendon, possibly resulting in jumper's knee or patellar tendinitis. Whether you are trying to recover from or prevent knee problems, proper strength training can improve knee health.
Anatomy
The kneecap makes all the motion of your knee possible. On the top side, it's attached to the super-powerful quadricep muscles, and on the bottom the patellar tendon connects the kneecap to your shin. When you straighten out your knee, the quadriceps contract and pull up the kneecap and the patellar tendon pulls up the shin. When you bend your knee, the hamstrings contract to pull the lower leg back while the quadriceps and patellar tendon lengthen.
Get Eccentric
Eccentric contractions happen when a muscle lengthens. When you go down stairs, your quads lengthen to control the move going down in an eccentric contraction. Your muscles generate more power in the lengthening phase of a movement than in the shortening phase. When doing a hamstring curl, for example, it is harder to lift the weight than it is to lower it. But eccentric exercise involves adding an extra challenge in the lengthening phase. For a hamstring curl, this could mean adding another weight over what you would normally lift with one leg. Then use two legs to lift the weight, but only one leg to lower it. Alternatively, a partner could add resistance with his hand as you lower the weight.
Physical therapists use eccentric exercises to help recover strength in injured tendons. If your knees usually hurt after exercise, and especially if they hurt during exercise or all the time, you should consult with a doctor and physical therapist to design specific exercises for your situation.
Exercises
Leg presses, side step-ups, lunges and squats all work the muscles supporting the knee joint. Knee extensions work the quadriceps, and hamstring curls isolate the backs of the legs. Toe raises develop the calves, and pointing and flexing your toes helps develop the anterior tibialis. A physical therapist or personal trainer can help you figure out if a muscle imbalance is causing a knee problem. If this is the case, you can work on developing the weaker muscles and stretching the dominant ones.
Stretches
Good lower-leg stretches to include in your regular workout routine include standing quad stretches, standing forward bends, standing hamstring stretches and standing calf stretches.
