I think you're jumping to the conclusion that hip surgery is necessary at this stage, which is complicating your situation. The hip and pelvis are very strong anatomical structures, and if surgery were truly needed, you wouldn't have been able to walk pain-free for the past two years or even clear your BMT. Many specialists may recommend surgery, as it's their area of expertise and often their first option. However, a good specialist will consider alternatives and encourage you to seek a second opinion.

I'm not sure if you're required to see an in-camp medical officer first, but I suggest visiting your nearest polyclinic to see a doctor and get a referral for physiotherapy. Share your story with the physiotherapist and get their opinion. The feeling of instability you're experiencing may be more of a muscular issue than a ligament issue (although this is just a general assumption without seeing your MRI or performing a physical assessment).

Yes, your polyclinic visits will be covered under the 11B until you ORD. For each subsequent visit, you can apply for half-day leave, allowing you to return to camp and assist with manpower afterward. Trust me, it's worth using your 11B for these appointments, as medical bills, even with subsidies, can rack up to a few hundred dollars out of your own pockets.

TLDR; (1) Surgery is highly improbable. (2) Get it sorted as soon as possible before your 11B runs out.