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Question from a reader: Can You Protect Your Self Against Osteoarthritis of the Knee

Posted Sep 04 2009 9:05am


I have two questions arising from your post below, which perhaps would be of interest to others:

  1. My left leg is substantially weaker than my right (arthritis in the left knee has led to weakening of the leg; total knee replacement in the right has allowed me to strengthen it).  The load tolerances of the two legs are very different.  I don’t have access to a Total Gym, but do have access to a leg press machine.  Would you suggest doing separate sets for each leg, or is it sufficient to do sets using both legs?  My worry is that if I do sets using both legs, my right (stronger) leg will do most of the work, leaving the left leg without enough load to actually challenge it and make it stronger?
  2. Are there good quad exercises that don’t require access to a Total Gym or leg press – i.e., that     one could do at home?  E.g. – doing two-leg squats with a Swiss ball behind your back against the wall?


Thanks for your questions, Jim, and I suspect you're right - others likely have similar questions.

Leg weakness is most often either due to muscle weakness or joint weakness with muscle weakness (occasionally, the bone will be the weak link in the leg but this is much less frequent than joint tissues). In the first case, your joint feels ok but you just don't have the muscle strength you need to squat on one leg. Probably in your case, at least for your left leg, you have some degree of joint weakness (and this term captures weakness of tendon, ligament, and cartilage) as well as muscle weakness. To strengthen the leg, you have to work from the inside out: cartilage or tendon/ligament first then up to muscle. If you try the reverse, strengthening muscle on top of a weak joint, usually you end up with a sore joint before your muscles experience much fatigue.

This is why I like the Total Gym or something similar to it. You need very low load (20-30% of body weight typically) and high volume (up to 30 minutes per day) of limited range squats to foster biologic change in the joint. Cartilage cells are mechanosensitive - meaning they respond to load. Too much load, and they fall apart. Too little load, and they weaken and waste away. So, you have to find the sweet spot - not too much and not too little and then train at that load, re-test periodically, and adjust your loads accordingly. Sometimes, depending on the machine, you can get close with a leg press at a gym. If you're trying to increase your joint strength, I would use both legs since the load will be very low. When you try muscle training, you can then train one leg at a time with different loads (so you would load test each leg prior to starting the program).

As for doing drills at home, what you described - the squat with the ball behind your back - is a decent muscle training drill but a poor joint training drill. It's at least body weight force and depending on how hard you push, can even be above body weight. Cycling, if you can regulate the force into your leg, can help. Walking or doing squats in a pool helps the joint as does swimming. "Quad sets", where you just tighten the quadriceps muscles with the knee straight, has been shown to improve synovial fluid quality and is a good joint drill.

Gyms are basically muscle building havens and are not terribly "joint friendly" which is why it is often difficult to implement a joint focused program in a gym. The tools - weight machines, free weights, etc - are built for muscle strengthening routines and the knowledge set within the gym - trainers, etc.- is also muscle based.

My advice is to do what you can to improve your joint health and strength first. Some people, even with very little cartilage, can greatly improve their function with this approach. The reason is not because they have generated new cartilage (there are case reports of this happening but no scientific studies that I know of) but because they've taken advantage of the body's amazing adaptability.

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