SENIORS! 11 Activities You Should Absolutely Avoid If You Have Knee Arthritis You are trying to stay active. You are trying to do the right thing. But did you know that certain "healthy" exercises can actually grind your cartilage down faster than doing nothing at all? For seniors with Osteoarthritis, the line between "building muscle" and "destroying joints" is very thin. In this video, we break down the 11 Worst Activities for arthritic knees. We explain the biomechanics of "Shearing Force" versus "Compressive Force" and why the popular Leg Extension machine at your gym is one of the most dangerous tools for a senior knee. We also discuss the hidden dangers of deep flexion (bending past 90 degrees), high-impact cardio, and uneven terrain. We don't just tell you what to stop; we give you the safe, low-impact alternatives that build the muscle brace you need without the bone-on-bone grinding. (Video Notes) 1. The Leg Extension Machine (Open Kinetic Chain) This is the #1 machine seniors should avoid. The Problem: It places the load on the ankle while the knee is the pivot point. This creates massive Shearing Force. It pulls the shin bone (tibia) forward away from the thigh bone (femur), grinding the cartilage. The Fix: Switch to "Closed Kinetic Chain" exercises like the Leg Press or Mini-Squats, where your foot is fixed against a surface. 2. Deep Lunges and Full Squats The Physics: The deeper you bend your knee, the harder the kneecap (patella) presses into the groove of the femur. The Danger Zone: Once you pass 90 degrees of flexion, the pressure on the patellofemoral joint skyrockets. If you have "bone on bone" arthritis, this is pure destruction. The Fix: Limit your range of motion. Do quarter squats or "sit-to-stands" from a high chair. 3. High-Impact Cardio (Running/Jumping) The Math: Walking puts about 1.5x body weight on the knee. Running puts 3x to 5x body weight. The Result: Arthritic knees lack the shock-absorbing cartilage to handle this. The shock travels straight to the bone, causing micro-fractures and inflammation. The Fix: Swimming, Cycling, or Elliptical machines provide cardio with zero impact. 4. Uneven Terrain (Hiking/Sand) The Risk: Walking on unstable surfaces requires constant micro-adjustments. This forces the knee to twist and rotate. The Damage: This twisting motion grinds the Meniscus (the shock absorber pads). The Fix: Stick to flat, predictable surfaces like tracks or pavement until your stability improves. 5. Prolonged Sitting (The "Rusting" Effect) Ironically, inactivity is an activity to avoid. The Mechanism: Cartilage has no blood supply. It gets nutrition from synovial fluid. This fluid only moves when the joint moves. The Consequence: Sitting for hours makes the fluid stagnant and the joint stiff. "Motion is Lotion." The Fix: Get up every 30 minutes, even just to march in place for 60 seconds. Medical Disclaimer: The content provided in this video and description is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Every case of arthritis is different. Some seniors with mild arthritis may tolerate lunges well, while others cannot. Listen to your body. If an activity causes sharp pain that lasts for more than 2 hours after stopping, you have likely overdone it. Consult your Physical Therapist for a personalized plan.