Don’t even think about tapping that grass.

When Dr. Scott Brotherton was recently asked what’s something that he would never do as an orthopedic surgeon, he said, “squats past 90 degrees,” also known as deep squats.

Two major types of deep squats are parallel — when you lower your hips until your thighs are parallel to the ground, typically bending your knees 110 to 120 degrees — and “a– to grass,” when you lower your hips even more, until your butt nearly touches the ground.

There’s been much debate on strength and conditioning forums over which squat is best for developing leg muscles and improving mobility. For Brotherton, one type of squat is a clear loser.

“Nothing says patella cartilage injury like a– to grass,” the Florida-based doctor said on TikTok.

The patellofemoral joint is where the kneecap (patella) meets the thighbone (femur) at the front of the knee. When you bend your knees for a deep squat, you can put excessive stress on that joint.

The stress can damage the cartilage that cushions the joint, especially if you are lifting heavy weights or using improper technique.

Knee cartilage injuries are common. Treatment often involves resting, icing and elevating the knee, wearing a brace, taking anti-inflammatory medicine and/or doing physical therapy.

If the injury is severe, surgery may be needed to stimulate growth of healthy cartilage.

Don’t let Brotherton’s warning scare you from doing squats. They are a great way to work your gluteus maximus, quadriceps and hamstrings, enhance stability and balance, strengthen your core, burn calories, improve posture and prevent muscle loss associated with aging.

Proper form is key. Experts say you should keep your knees aligned over your toes, shift your weight back into your heels, rotate your pelvis backward and squeeze your glutes.

Be careful not to hunch your back, overextend your hips, let your chest drop down or use too much weight to start. Stop if you experience knee pain.