Objectives: The purpose of this study was to evaluate if the restoration of functional joint stability in ACL-injured patients/shoulder instability could be estimated by stimulation of proprioception and neuromuscular control during rehabilitation programme or if operative stabilisation should be performed previously. In addition, the study was to examine a shortterm and long-term efficiency of various therapeutic approaches in joint injuries by monitoring the indicators of joint functionality in the early stages (from one month to one year after injury/operation) or in the later stages of injury (20 years upon injury). Finally, the aim of the study was to find out how various therapeutic approaches affected the occurrence of osteoarthritis as a chronic knee injury complication. Patients and methods: We analysed 83 ACL-injured patients and 53 patients with shoulder instability treated operatively (ACL reconstruction/operative shoulder stabilization followed by rehabilitation) and non-operatively (rehabilitation without ACL reconstruction/operative shoulder stabilisation). In some patients operative joint stability of the knee/shoulder was performed. All the patients underwent a functional rehabilitation programme except those who experienced a knee joint injury 15 to 20 years before and were tested for joint functionality and neuromuscular control only 15-20 years following the injury. Subjective and objective methods of testing knee/shoulder joint function were used, including testing the proprioception and neuromuscular control (SportKAT 2000), measuring isometric muscular strenght using hand-held dynamometre (Spark Instruments, USA), estimation of knee function (HSS scoring system) and shoulder function (ASES scoring system), and radiological estimation of the knee osteoarthritis degree. Results: Having applied the Sport KAT method by setting static and dynamic balance indexes, a dysfunction of proprioception and neuromuscular control was found in the maintenance of balance as well as static and dynamic joint stability in the observed patient groups. Exercises that include stimulation of proprioception, as a part of the rehabilitation procedure following ACL injuries/shoulder instability, soon lead to an improvement of both balance indexes. However, no long term impact of rehabilitation on the improvement of the balance indexes was noted. In fact, if the above exercises are not conducted on a regular daily basis, the balance indexes will deteriorate. On the other hand, after operative joint stabilization the balance indexes tend to improve, thus establishing a ‘normal’ balance. Furthermore, although proprioception exercises in the course of post-injury rehabilitation of the knee/shoulder show improvement in the overall result of applying the subjective-objective method (HSS/ASES scoring system) of estimating knee/shoulder function, nevertheless the short-term and long-term results achieved by operation and post-operative rehabilitation were significantly better, thus proving that this therapeutic approach yields values comparable to the normal ones. Irrespective of the fact whether a operative joint stabilisation has been conducted or not, post-traumatic knee osteoarthritis in ACL injuries occurs in the injured knee rather than in a healthy leg and is more likely to be associated with a meniscus-related injury. Conclusion: Functional stability of the knee/shoulder joint is dependent on coactivation of the muscles surrounding the joint as well as reactive neuromuscular characteristics. In order to eliminate the neurosensory (proprioceptive) deficits in ACL injured/shoulder instability patients and to restore dynamic stabilization of the joint, exercises stimulating the neuromuscular mechanisms are necessary. This suggests that balance and neuromuscular control play a crucial role in knee/shoulder joint stability, protection and prevention of injuries.