Impact of Proximal Conjoint Tendon Injury on Return to Play in the BF–ST Complex: A Prospective MRI-Based Study

Background: Proximal hamstring injuries involving the biceps femoris–semitendinosus (BF–ST) conjoint tendon are clinically challenging, yet the prognostic impact of full-layer conjoint tendon (CT) injuries remains unclear. This study aimed to determine whether CT involvement prolongs the time to return to play (RTP) compared with isolated BFLH or ST injuries. Methods: A prospective cohort of 41 university rugby players with acute proximal BF–ST complex injuries was evaluated using standardized physical examination, ultrasonography, and MRI. Injuries were classified by Type (I: full-layer CT; II: BFLH-only; III: ST-only), Zone (A–E), and Grade (0–3). RTP was defined as full participation in team training or competition. RTP differences among Types and, within Type I, across Zones and Grades were analyzed using appropriate parametric or non-parametric tests. Results: Type I injuries required significantly longer RTP (11.4 ± 4.8 weeks) than Type II (5.3 ± 2.4 weeks) or Type III (4.0 ± 1.7 weeks). In Zone C, bilateral involvement of both BFLH and ST resulted in longer RTP than unilateral BFLH injury. Within Type I, Zone A (origin detachment) showed the longest RTP (20 weeks), exceeding Zones B and C. Higher Grades were also associated with prolonged recovery. Conclusions: Full-layer CT injuries represent a distinct clinical entity with markedly delayed RTP compared with isolated BFLH or ST injuries. Classification that distinguishes CT involvement provides useful prognostic information and may enhance RTP planning in athletes.