Case Report: Cristiano Ronaldo’s Patellar Tendinopathy

Tendinopathy describes a tendon disorder that typically results from overuse; however, PT may also occur from blunt force trauma (e.g., kick) directed to the patellar tendon⁽⁴⁾. In a landmark paper, clinician-researchers from Melbourne’s La Trobe University proposed that tendon pathology exists as a continuum in which exceeding a tendon’s load tolerance may lead to the development of tendinopathy⁽⁵⁾. Without intervention, this disorder can intensify over time as severe structural disorganization and degradation may occur to the extent that regions of the tendon exhibit cell death and the risk of a partial or complete tear increases^(6–9). Therefore, early intervention may minimize the risk that it becomes a degenerative condition⁽⁶⁾. Once developed, PT symptoms can persist for a protracted period, with symptoms lasting between 19-32 months, so treating this disorder may be a prolonged effort^(10,11).

Highly explosive male athletes who perform a high volume of sports training and competition experience an elevated risk of developing PT, and Cristiano Ronaldo certainly fits this profile^(12–15). With his ability to reach impressive heights when leaping for a header and elite speeds when sprinting, Ronaldo was able to subject his patellar tendons to a considerable magnitude of high-rate loading. Furthermore, he would have been experiencing a high volume of cumulative patellar tendon loading from lower velocity running, given that professional football players cover an average of 10.8km (6.7 miles) per match^(16–19).

Load management and the kinetic chain

Because PT typically stems from the excessive load on the tendon with high-rate energy storage activities, temporarily reducing the volume of these stressors may accelerate recovery⁽²⁾. Beyond playing fewer minutes, decreasing the volume of these aggravating activities may not be feasible during competitions for in-season athletes; however, practitioners may influence load through training modification (time and intensity). Coaches could examine all provocative training activities to determine if they can make any substitutions to induce similar favorable effects while reducing plyometric loading.

For instance, a football player may commonly sprint to train his maximal speed and perform longer interval runs to train his aerobic capacity and anaerobic endurance. If these activities are provocative, practitioners can use alternative training modalities to maintain these physiological qualities without subjecting the patellar tendon to the same degree of high-rate energy storage and release. For example, cycling can achieve the desired cardiovascular adaptations, while athletes can train sprint speed through a combination of resistance training exercises that enhance high-velocity force production of the key muscle groups which contribute to sprint performance (see table 1)^(20–23).

Table 1: Joint movements whose strength significantly correlates with sprint performance^(24–27)

Furthermore, resistance training is a critical component of PT management. Strengthening the hip extensors and ankle plantarflexors muscles may allow an athlete to absorb more energy at the hip and ankle joints relative to the knee joint during various athletic maneuvres⁽²⁸⁾. Doing so may help reduce patellar tendon loading during provocative activities such as jump landings or rapid direction changes, which require simultaneous movement at the knee, hip, and ankle joints⁽²⁹⁾. While hip and ankle exercises can be valuable additions to an athlete’s program, no substitute exists for resistance training exercises that directly load the patellar tendon.

Knee extension exercises

Given that PT arises from excessive tendon loading, intentionally subjecting the tendon to further high load activities may seem counterproductive compared to rest. However, shielding a patellar tendon from stress can induce pathological changes and steadily decrease its load tolerance, so prolonged complete rest is not a viable rehab method despite any transient symptom relief ^(30,31). In contrast, loading the patellar tendon through low-velocity knee extension exercise can effectively treat PT^(32,33).

Researchers have extensively studied the eccentric unilateral decline squat for PT treatment, which is commonly programmed for three sets of 15 reps twice daily (see figure 2)^(33,34). Several studies have found interventions using this protocol to be quite effective for reducing pain and improving function after 4–12-week programs and even during long-term follow-ups⁽³³⁾. However, as practitioners typically measure PT pain with the eccentric unilateral decline squat, this exercise can be fairly provocative, so it may not be ideal for some in-season athletes already experiencing tendon pain from sports activity^(35–37).

On the other hand, athletes with PT can experience transient analgesia acutely after performing a few sets of isometric or slow (e.g., seven-second reps) concentric-eccentric knee extension exercises with moderately high loads (see figures 3 and 4)^(38–41). Specifically, these isometric protocols typically consisted of five sets of 45-second holds loaded with 70-80% of participants’ maximal isometric torque, while the dynamic bouts consist of four sets of eight reps loaded with 80-100% of the athletes’ eight-rep max^(38–41). When athletes perform these protocols regularly over a short-term (i.e., four weeks), both training approaches yield sustained reductions in pain for in-season athletes^(40,42,43). Although dynamic and isometric training yield analgesic benefits, isometric training may induce a significantly more potent analgesic effect than dynamic training^(38,40,41). Furthermore, a significant increase in knee extension strength may persist along with the analgesia for at least 45 minutes following exclusively isometric knee extension exercise⁽⁴¹⁾.

Athletes with PT who seek pain relief before frequent training or competition may perform relatively high weekly volumes of additional exercise, so coaches and practitioners must account for the extra fatigue that can result. To minimize any interference with training or competition from reasonably challenging high-frequency loading bouts, isometric exercise is likely superior to dynamic exercise, which includes concentric and eccentric actions. Eccentric actions can generate considerable muscle damage and induce greater soreness and more prolonged impairment in force production than isometric actions^(44,45). Moreover, isometric exercise may also be less metabolically taxing than conventional dynamic exercise, primarily due to the higher energetic cost of concentric actions^(46,47). 

Conclusion

While isometric training can benefit in-season athletes, favorable clinical outcomes occur in response to knee extension training performed with different contraction types. Practitioners can use various exercises, loads, frequencies, and volumes (e.g., Heavy slow dynamic and blood flow restriction training) to achieve favorable outcomes (see figures 5 and 6)^{(32,33,48–50)}.

Despite the many differences in program variables, the key similarity shared among these interventions is that they consistently load the patellar tendon through challenging sets of low-velocity knee extension exercises. In isolation, knee extension exercise can be an effective treatment, but strengthening the rest of the kinetic chain and modifying plyometric exposure outside of competition also merit inclusion.      

As Cristiano Ronaldo personally experienced, PT can be a meaningful obstacle for an in-season athlete; however, resolution can occur if practitioners and athletes take action early. In the seasons following his onset of PT, Ronaldo apparently experienced a complete recovery as he continued to ascend to rarified air by leading Real Madrid to three consecutive Champions League victories, a historic feat not accomplished since 1976.   

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