I am sorry to hear about your medical problems. The various causes of knee
locking are torn medial
meniscus, mis-aligned knee cap, osteoarthritis, knee arthritis, torn lateral meniscus, osteochondritis dissecans, recurrent patella dislocation, chondromalacia patella, knee alignment problem, knee fragment or knee cartilage disorder. True knee locking is caused by either a torn piece of cartilage, or a loose bone fragment due to a bone disorder called osteochondritis dissecans.