My guess would be a back problem (I'm assuming a partial ligament tear has been ruled out). Try laser therapy, acupuncture and/or chiropractic. Rafi jumped very high, came down hard and about an hour later could barely walk. I took him in for chiropractic the next morning and the vet did laser therapy and Rafi went from barely walking to doing great!
Ruth & the 4 Legged Rescue Gang
Rafi the malaroo
Gio & Varda, the krazy kittens
....In my heart: