Knee brace maybe?

My boy is a 12 yr old desexed Male Moodle. His very much still a pup as far as he knows. His never had knee/leg problems. 3 days ago while playing with a friends new puppy he hurt his knee posssssibly hip, but fairly sure knee (rear left) he yelped and it appeared visually ok, but he kept it dead straight, couldnt put weight on it for about an 30 min then he came good. He was panting heavily in pain at time. Since this however, its as though maybe something slips out randomly, while walking, and he briefly cant use the leg, sometimes yelps but not always, keeps it straight, then it comes good. I am wondering if maybe a knee brace would help prevent the possible joint slip. Its not hurting him between incidents. He doesnt understand the concept of aging and slowing down a bit. I cannot crate him to force rest as his too anxious.  Brace maybe? Or maybe shave and tape? Or maybe bandage? Moodle (maltese x poodle). Picture just to show him, he just never seems like an old boy, his energetic and happy and youthful. Should i be worried? Im freaking out...

Aw what a beautiful boy!   Im sorry he's hurt his leg.   From your description, there are three or four possible problems but for none of them would 'put a knee brace on at home' have been my instinctive solution.   Really, the correct treatment depends on the cause and some of the main knee injuries - dislocation, fracture, cruciate disease and luxating patella - can be diagnosed by a vet, palpating the joint.  They would also give appropriate pain releif and diagnose rest and sometimes surgery.  Therefore, contacting your vet to be triaged for an appointment would be the best way forward for this.  Wishing your gorgeous Moodle  a speedy recovery