Knee wraps are essential in competition powerlifting because they cause a high amount of elastic energy to be stored during the descent of the squat, and this energy is released during the upward phase. This energy release enables more weight to be used and the lift to be performed faster. Also, because the wraps alter the technique of the squat (such as by restricting the motion of the hip joint), powerlifters must spend a good deal of time training with knee wraps as well.
However, I’m not a fan of knee wraps for typical trainees or bodybuilders. One problem with knee wraps that cover the patella (kneecap) and are pulled too tightly is that this may increase the friction between the patella and the underlying cartilage, because the wraps compress the kneecap into the thighbone. The theory is that this effect may increase the risk of injury and knee pathologies such as arthritis. In fact, in one study comparing the incidence of osteoarthritis provide pain relief for many conditions. That being said, how about changing your approach from trying to treat the symptoms to fixing the cause? The source of this type of injury is often a relative weakness in the vastus medialis oblique (VMO), a quadriceps muscle that crosses the knee joint and thus is an important muscle for maintaining knee stability. If the VMO is weaker than the other quadriceps muscles, this imbalance can cause an unnatural tracking of the kneecap.
When you see a trainee’s knees collapse inward during squatting, this is often a case of weak VMOs. Trying to correct this problem initially with full squats may not be wise, as the altered biomechanics of the knee could worsen the condition. Instead, I have most trainees who demonstrate this fault first focus on special stepup exercises, such as the Petersen stepup, which begins with the heels elevated and is performed at progressively higher elevations. Eventually the stepups enable these athletes to progress to conventional stepups and then to full squats.
What exercises are taboo? I’ve heard negative things about upright rows, dumbbell lateral raises, hyperextensions, and dips.
Well, at least you didn’t say full squats—dispelling that myth has been a lifelong challenge of mine. Getting back to your question, it’s not so much that an exercise is “bad” but that it can become bad if poor technique or poor training methods are used. Let’s start with training methods.