Does anyone know of exercise or modality(ice/heat/tens) protocols that are supposed to increase joint cartilage bed thickness? This is excluding stem cell injections. I imagine that such a protocol would be more effective with children and younger athletes who still have stem cells present in their joints to create the repair. However I don't know if any research that measures stem cell density inside of joints for different age populations or for different exercise programs.
Articular cartilage, which covers the ends of bones in all synovial joints is avascular. Without a blood supply it is unable to heal or regenerate. Over time the loss of this cartilage is what causes the condition known as osteoarthritis.
The modalities you've listed are indicated for swelling / healing and pain management. So they'll only help with secondary symptoms that are seen with cartilage loss.
Kobe Bryant had a non FDA approved treatment called Regenokine done in Russia, you can read about the procedure here.