Yep, having had knee surgery before, the Standing Terminal Knee Extension exercise is definitely one that I’m familiar with! 🙂 I totally agree that defining what type of knee problem your client has and whether the physician has given him any ‘restrictions’ would be a great place to start. Also, I cannot imagine that the high-intensity/plyometric activity of an Insanity workout is great for his knees, and wondered (out loud) as I read your question as to whether your client’s physician KNOWS that he is doing such a high intensity/ballistic/plyometric exercise? I DOUBT that the physician knows about this, and doubt even more that if the physician did know, that he/she would condone it. You may want to have your client discuss this with his physician moving forward, or better yet, have that discussion with the physician yourself with your client’s permission.
Once you have a handle on the nature of your client’s knee issue, and a ‘conversation’ with his physician, you will be in a much better place for planning his workouts moving forward.
I personally don’t feel comfortable giving advice about how to approach your client when I haven’t given him an assessment.
You might want to collaborate with his physician to see the extent of the damage to his knee, find out the doctors diagnosis and then do research on the condition as it relates to exercise.
If you learn that his condition is outside the scope of your preparation, it might be a good idea to refer.
All the best!
Is he actually performing the jumping portions? How much pounding/how much pain is he having with the impact? How’s his gait? Does he have full knee extension during swing-thru and with heel strike? Knee stay bent when standing still? Hows the hip strength and ROM?
Ironically, knee pain (and most joint pain) comes from weakness somewhere else, usually in the joint above or below the painful one, unless there was trauma to the joint itself. But even then, over time, it can get worse because of overcompensating.
Strengthening the knee will help the symptoms, maybe short-term. Assess and find his weakness and ROM limitations, probably in the hips and more than likely in the HS, if it’s OA. You’ll do him a greater good in the long run. Would benefit from stretching of the hamstrings and strengthening to the hip external rotators and abductors, in addition to the TKE’s.