The Tegner score is a scoring system to gauge how disabled one is from one's knee problem in terms of activity.
ICRS Recommendation Document. Patient-Reported Outcome Instruments for Use in Patients with Articular Cartilage Defects Roos EM, Engelhart L, Ranstam J, Anderson AF, Irrgang JJ, Marx RG, Tegner Y and Davis AM. Cartilage. 2011 Apr; 2(2): 122–136.