Isokinetic strength evaluation of muscle action in both (concentric-eccentric) contraction is an important comprehensive evaluation for rehabilitation and conditioning programs formed for athletes that highlights the training process. The study's main purpose was to identify strength deficits and bilateral imbalance between (agonists–antagonist) knee muscles accompanied by the hamstring injury to establish an isokinetic conditioning protocol. Research sample was one of the Egyptian national squash team (males under 19 years), who suffered from chronic strain in his left hamstring origin while at the preparatory phase for the world championship (Namibia 2014). The design of the study consisted of two stages using isokinetic system for all modes of contraction. First (5 weeks) of isometric rehabilitation, and second (5 weeks) of isokinetic training. The results revealed that final (H:Q) ratio calculated after applying the conditioning protocol for the dominant leg was (92.48%), and the injured non-dominant leg was (87.50%), compared to the initial measurement of (91.15%) and (67.68%) respectively. Therefore, imbalance and strength deficits between hamstring and quadriceps were highly improved, in addition to (19.82%) amelioration in the injured non-dominant leg strength balance and enhancement in all isokinetic variables tested. Accordingly, subject's technical performance was enhanced in the (SSET) test to reach maximal speed of (2.45 m.s-1) and endurance of (stage 9, run 2).