In the study by Widuchowski et al(14), some type of chondral lesion was found in 60% of the knees operated, of which 67% were classified as osteochondral or chondral lesions, 29% as osteoarthritis, 2% as osteochondritis dissecans and 1% as other types.
Your account balance, also referred to as your current balance, is the total balance on your account, including any activity since your last statement. That last bit of the definition is probably the best way to differentiate the pair.
The terminal at the company sends a message to the bank that you wish to spend $50 from your account. The bank agrees and puts $50 aside for the transaction, and now, though current balance in your account is still $200, the available balance is $200-$50 = $150 and not $200.