This article places squash on its list of sports with the highest risk of joint injury, while it places tennis on its list of lowest risk sports. Assuming proper protective equipment is worn (e.g. goggles), does squash still have a much higher injury risky than tennis?
It's been a long time since I've played, but I could see why they'd consider squash more dangerous.
First, it's pretty much tennis, but shoved into a shoebox. There's no division between the players, and they have less reaction time. This all adds up to an increased probability of running into each other, and imparting damage to joints, e.g., sprained ankles, sprained wrists, etc.
Second, the rackets are lighter and the handles are much shorter and smaller in diameter, than in tennis, while the strokes are either similar or smaller, but surely more compact. This is fairly more difficult to articulate through text, but here goes:
In tennis, the way to avoid joint injuries is to strive for near-perfect technique, which will minimize pressure on the joints. This can be achieved in a few ways:
Hold the racket with the butt cap in the palm of your hand.
This allows you to hold the grip looser. Which not only aids in staving off carpal tunnel, but can also allow the ball to go in the intended direction if accidentally shanked. I do not believe this is possible in racketball since the handles are significantly smaller and the racket is more likely to fly out of your hand. Gripping hard, and frequently doing so, causes carpal tunnel, cubital tunnel.
The motion of hitting the ball in tennis is similar to bunting the ball in baseball.
I explain this to people by telling them to imagine throwing the racket at the ball instead of hitting the ball with the racket. This also encourages looser grip and less tension in the body. Again, with racketball, since there's not as much mass to the racket, and since the stroke is so much more compact, I don't believe this is possible to accomplish, or at least not to the same scale. This means you're relying solely on muscle for power, which will cause swelling in the muscles, and pressure on the joints, not to mention higher impact on the joints since you're actively gripping harder, again, causing carpal tunnel, cubital tunnel, etc.
Step into the ball for power.
While this is obviously possible to do in racketball, since the proximity to other players is so small, it makes it more difficult to do consistently. Since you're not stepping into the ball for power, this means the only other way to get power is to "muscle through it", which encourages more tension in the muscles and in turn more pressure on the joints.
After dealing with the fallout of cubital tunnel syndrome, which resulted in nerves being surgically relocated, I pretty much understand the idea is to avoid tension as much as possible. I hope that helps.