The free fibula flap has been one of the most important microvascular grafts for orofacial reconstruction for over 30 years and is mainly used after tumour resection of the lower jaw. Even though the complication rate at the donor site is considered low, the information provided varies greatly in some cases. In particular, restrictions in the stability and balance of the leg and their effects on lives of patients have been described very inconsistently to date. Against this background, patients of the Department for Oral and Maxillofacial Surgery at the University Hospital Giessen were examined more closely for the first time after fibula transplantation. Between December 2014 and January 2018, 68 of a total of 119 patients, which corresponds to a rate of 57 %, could be examined for their donor site morbidity. The examination took place on average 47 months postoperatively (2 months - 14 years) and focused particularly on restrictions in the function of the leg and the impact on daily life. As an indicator of balance and stability, the ankle joint was selected, in which the fibula is involved as one of 3 bones. Two specific test procedures were used for this purpose, the Star Excursion Balance Test (SEBT) as a practical test of ankle function and the Foot and Ankle Disability Index (FADI) as a questionnaire to assess quality of life dependent on the lower leg function. The majority of patients (97 %) underwent surgery for a tumor, the rest was due to necrosis and atrophy of the jaw bone. The most frequent tumor (69 %) was a squamous cell carcinoma. In 76.4 % of the cases an osseomyocutaneous graft was chosen and in 73.5 % the donor site was closed with a split skin graft. The inpatient stay was on average 20 days and was prolonged for squamous cell carcinoma and osseomyocutaneous transplants. The postoperative pain intensity was indicated with an average of 3.2 on a scale of 0-10 and 88 % of the patients were pain-free after 3 months at the latest. With split-skin covering, the pain lasted longer and wound healing disorders occurred more frequently. Temporary complications at the donor site occurred in 41 % of the patients, mainly wound healing disorders, while 16 % experienced long-term complications, mostly paraesthesia and chronic pain. In 10.3 % of the patients foot lifter weakness was observed, indicating damage to the fibular nerve. 3 % of the patients were dissatisfied with the entire operation, 6 % with the aesthetics of the donor site. In the SEBT, the participants achieved significantly shorter values in all 8 directional axes with the operated leg as the stance leg. On average, the difference to the healthy leg was 4.5 %, which corresponds to studies on chronic ankle instability (CAI). The FADI score of 89.4 % is also within the range of the CAI studies, according to which there are limitations, but these only have a minor impact on the lives of the patients. When tested for statistical correlations, low p-values were found between squamous cell carcinomas, osteomyocutaneous grafts, split skin closure, wound healing disorders and fibular nerve lesions, among others. The FADI seems to be negatively influenced by these values, whereas no statistical correlations were found between FADI and SEBT. Overall, the donor site morbidity in our study is also in a low, acceptable range and thus corresponds to the literature. Unfortunately, due to inconsistent methods and collectives, there are often strong fluctuations between individual studies. Even in the only study that also uses SEBT and FADI after fibula transplantation, the SEBT values are in contradiction to ours. Nevertheless, SEBT and FADI seem promising for patients after fibula flap surgery and have many advantages due to their simplicity. However, additional studies with pre- and postoperative comparisons and control groups are necessary to further establish these methods.