@aspine - PMR can sometimes be difficult to diagnose due to the number of conditions that can mimick PMR. The National Organization for Rare Disorders has the following information under related conditions. You might want to discuss it with your PCP.

"Polymyositis is a rare inflammatory disease characterized by degenerative changes in muscles and supporting connective tissue. Muscle weakness may occur rapidly and affect the neck, trunk, and upper arms and legs. Joint pain, swelling, and tenderness may be present. Eventually, it becomes difficult for affected individuals to rise from a sitting position. In some cases, individuals may have difficulty climbing stairs, lifting objects, and reaching overhead. The exact cause of polymyositis is unknown, although the interaction of inherited, viral, and environmental factors may play a role." --- Polymyalgia Rheumatica: https://rarediseases.org/rare-diseases/polymyalgia-rheumatica/

Also, exercise does play a role in PMR and can help - "Both exercise and rest play important roles in PMR treatment. Regular exercise is essential for maintaining joint flexibility, muscle strength and function. Good forms of exercise include walking, riding a stationary bicycle and exercising in a pool. Rest is also necessary to give the body time to recover from exercise and other activity." -- Polymyalgia Rheumatica: https://www.arthritis.org/diseases/polymyalgia-rheumatica

I don't think you are alone with leg strength. Even though my PMR is currently in remission I have similar concerns. It's difficult for me to get up from the ground although I am 78 🙂. I try to do leg strengthening exercises daily along with some upper body exercises.