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We speculate that chronic recurrent soft tissue fatigue or overload due to patellofemoral imbalance could cause anterior knee pain. However, many chondropathies can be asymptomatic due to the biomechanic defence strategies used by the patients. Moreover, we emphasize the importance of the passive restraining structures in patellar stability, in contrast to the role of muscle function advocated by some authors. This could explain why an exercise rehabilitation program could be unsuccessful in improving patellar instability, as it occurred in our cases. Finally, these cases highlight the need for surgeons to be more judicious in their surgical selection for patellofemoral instability and serve as a warning for the generalized use of lateral retinacular release. The question we ask ourselves is: Is there a place for the isolated lateral retinacular release? In this sense, it would be interesting to consider the lengthening of the lateral retinaculum described by Roland Biedert as an alternative to lateral retinacular release.

Surgical procedures for reconstruction of a torn anterior cruciate ligament (ACL) have changed considerably over the last 30 years. They have evolved from open surgery to advanced all-inside endoscopic techniques. Arthroscopic transtibial ACL reconstructions have been largely used in recent decades. However, a trend toward more anatomic ACL reconstructions has started in recent years due to the high rates of persistent rotatory instability observed after vertically oriented graft. Placing a single femoral tunnel at the center of the anatomic insertions of the ACL may restore the rotational stability of the knee as well as a double-bundle technique. A thorough knowledge of the anatomical attachment sites of the ACL is required for precise anatomic ACL reconstruction.

Deep venous thrombosis (DVT) and its most fatal complication, pulmonary embolism (PE), are manifestations of a single disease entity, that is, venous thromboembolism (VTE). VTE is a common and clinically relevant complication of major orthopedic surgery. Indeed, it is associated with a significant morbidity and mortality. With the advent of arthroscopic surgery, the incisions have become smaller and the rehabilitation faster, but in spite of this, there are reports of VTE following arthroscopic surgery. Most of the research is related to arthroscopic surgery alone. We have reviewed the literature and have found the DVT complication rate to be between 0.15 and 18 % in lower limb arthroscopic standard surgery (see Sect. 33.2). Arthroscopically assisted surgeries, like anterior cruciate ligament (ACL) reconstruction, are more aggressive than standard arthroscopy, take a longer time, and therefore should potentially be more predisposed to DVT. However, Jaureguito et al. [20] reported that patients undergoing arthroscopically assisted surgery had only a slightly higher incidence of DVT as compared to routine arthroscopic surgery, but this difference was not statistically significant. These findings in agreement with those of Hoppener et al. [15] did not find a higher DVT risk in ACL reconstruction or in other more complex arthroscopic procedures. Also, Hetsroni et al. [13], after reviewing more 400,000 outpatient arthroscopies, found no increase in the PE risk when the arthroscopic procedure involved an ACL reconstruction or a meniscal repair, surgeries that theoretically would have a higher risk of VTE.

Interest in isolated tears of one of the two bundles of the anterior cruciate ligament has increased over recent years. It is thought that by only reconstructing the ruptured bundle while preserving the uninjured bundle contributes to faster graft healing, a better proprioceptive outcome as well as faster recovery. However, this is still to be proven. This chapter describes the difficulty in assessing and confirming partial anterior cruciate ligament injuries. Attention to clinical examination and imaging must also be done. The main purpose of this section is to detail the arthroscopic examination and reconstruction of isolated anterior cruciate ligament bundle ruptures.

Anterior knee pain (AKP) is a frequent complaint and well-documented problem after anterior cruciate ligament (ACL) reconstruction [1, 10, 11, 14, 17, 19, 20, 22–24, 27, 28, 30, 33, 41, 42, 47, 48, 50, 52–58, 61]. AKP is a diagnosis based on symptoms and clinical signs. The severity of pain ranges from a mild nuisance to severe pain that prevents one from performing daily living activities. Thus, depending on pain severity, it could be considered as a complication or a normal postoperative outcome. The presence of AKP can interfere with patient’s satisfaction after ACL reconstruction. In fact, AKP is an outcome predictor after ACL reconstruction. Thus, Bartlett et al. [4] have observed that the grade of patient satisfaction after ACL reconstruction correlates more strongly with the absence of pain than with any other variable assessed. Also, Heijne et al. [20] have shown that a low degree of AKP is the most important predictor for a good clinical outcome 12 months after ACL reconstruction. Therefore, prevention of AKP after ACL reconstruction would be a crucial key for surgery success.

Rotational stability plays a key role in restoring normal function of the knee after anterior cruciate ligament (ACL) reconstruction [15]. Therefore, the accurate evaluation of rotational stability would be an important outcome indicator of ACL reconstruction. The only clinical test for examining rotational stability of the knee is the pivot-shift test [46]. Most surgeons now recognize the importance of the pivot-shift test. A positive pivot-shift test, regardless of the grade, is indicative of a functionally deficient ACL and remains the sine qua non indication for surgery [13]. Moreover, it is predictive of poor subjective and objective outcome, patient discomfort, disability, failure to return to previous level of sport, increased scintigraphic activity in the subchondral bone, and development of osteoarthritis of the knee at long term [20, 21, 24, 50]. Therefore, accurate assessment of the pivot-shift phenomenon is clinically mandatory. However, currently, the gold standard for evaluation of rotational knee stability after ACL tears in the office is based on patient history and subjective un-instrumented physical examination, the pivot-shift test, which is highly variable and dependent on examiner’s skill and experience and has both a low sensitivity and low interobserver reliability [32]. Moreover, the rotational load applied to the knee during the pivot-shift test is much lower than the load applied to the knee during sports activities. Furthermore, patient guarding can lead to false negatives. Moreover, clinical pivot-shift test cannot evaluate small rotational differences between the pathological/reconstructed and the healthy contralateral knee. Finally, the pivot-shift test is often only testable during examination under anesthesia. In our series, the sensitivity of the physical examination with the patient awake was 37.5 %, whereas the sensitivity of the physical examination with the patient under general anesthesia was 87.5 % [42]. Therefore, a negative clinical pivot-shift test does not necessarily involve a normal rotational stability. Currently, however, there is no simple, commercially available device to measure knee rotational stability in vivo.

Both the meniscus and ACL are frequently injured in sports-related trauma. Regardless of the knee stability obtained after ACL reconstruction, meniscectomy accelerates degenerative joint changes. Although the ability of the meniscal tissue to heal is known to be limited, its repair at the time of ACL reconstruction has the best chance of healing and so it is currently done by most knee surgeons. ACL-deficient patients with a significant meniscal defect, particularly on the medial side, might benefit from the increase in stability provided by a meniscal transplantation carried out at the time of ACL reconstruction.

The anterior knee pain syndrome and functional patellar instability in the active young person is one of the most complex knee disorders, with a multiple factor and highly variable pathogenesis, with intermingling mechanical and neurological factors. Probably the neural factor is the cause of the well established symptoms in patients with certain mechanical anomalies and a knee overuse.

There are many diagnostic clinical tests (e.g., apprehension patellar test or the moving patellar apprehension test), outcome measures (general health and knee scales [IKDC form, Kujala scale, Fulkerson scale, Lysholm knee scoring scale, Tegner activity level scale, short form-36]), and instrumented measurements of patellar mobility (static stability), to assess lateral patellar instability.7,10,15,16 However, according to Smith and colleagues,15 the sensitivity/specificity – reliability/validity of such tests and outcome tools remain unclear for this patient population. These authors conclude that further work is needed to assess the appropriateness of these tests and outcomes.15Moreover, there are many surgical techniques to treat patients with chronic lateral patellar instability, all of them based on level of evidence IV or V.4 This is due, in part, to the lackof prospective randomized trials, and also to the lack of an objective, suitable, reliable, valid, and reproducible noninvasive in vivo method to evaluatelateral patellar instability in the clinical setting. This makes it difficult to compare different surgical treatments in order to find the best surgical technique to treat patients with chronic lateral patellar instability.

We review the pathophysiology of anterior knee pain in the young patient. Emphasis is placed on newer findings. We have developed what we call the “Neural Model” as an explanation for the genesis of anterior knee pain. We have demonstrated a neuroanatomical basis for PFPS in the young patient and the clinical observation that the lateral retinaculum may have a key role in the origin of this pain. According to our studies we hypothesize that periodic short episodes of ischemia in the lateral retinaculum could be implicated in the pathogenesis of anterior knee pain, at least in a subgroup of anterior knee pain patients, by triggering neural proliferation of nociceptive axons (substance P positive nerves), mainly in a perivascular location. Our findings are compatible with the tissue homeostasis theory widely accepted currently to explain the genesis of anterior knee pain. If the “neural model” of anterior knee pain proves to have a certain validity, it would lead in many cases to therapeutic recommendations to alleviate pain more effectively and safer than the attempts to correct “malalignment.” Moreover, we believe that instability in patients with PFPS can be explained, at least in part, because of the damage of nerves of the lateral retinaculum which can be related with proprioception. Our findings, however, do not preclude the possibility of pain arising in other anatomical structures such as infrapatellar fat pad, synovium and subchondral bone.

Anterior knee pain is a common symptom, which may have a large variety of causes. Although, patellofemoral malalignment (PFM) is a potential cause of anterior knee pain in young patients, not all malalignments are symptomatic. To think of anterior knee pain as somehow being necessarily tied to PFM is an oversimplification that has positively stultified progress towards better diagnosis and treatment of patients with anterior knee pain syndrome. PFM could be the single culprit for the pain but it is also possible that it bears no relation whatsoever with the patient’s complaint or that it is only partly to blame for the problem. PFM can exist without anterior knee pain, and anterior knee pain can exist without PFM. There are many causes of anterior knee pain, some of them related to PFM and many more not related to PFM. Likewise, we should bear in mind that there are teenage patients with anterior knee pain who lack evidence of organic pathology (i.e., their condition is of a psychosomatic nature [21]) and also patients who suffer from the “malingering syndrome”. In this chapter we analyze uncommon causes of anterior knee pain, emphasizing the fact that not all malalignments are symptomatic.

Unfortunately, many orthopedic surgeons believe that the definite solution for eliminating anterior knee pain in a young patient with multiple operations is the patellofemoral prosthesis (“The Great Solution”). But, they fail to ask themselves the most important question; what is causing the pain? When a patellofemoral prosthesis is implanted in these young patients without finding out the cause of the pain, a more serious problem could be created with a worse solution (“The Great Problem”). The cases we present spotlight this abuse.

Stair climbing is a demanding locomotor task frequently performed during daily activities. It is well-known from a functional point of view that going up and down stairs, requiring high levels of quadriceps activity, is one of the most painful and challenging activities of daily living for subjects with anterior knee pain. Moreover, it is universally accepted that going downstairs is more challenging that going upstairs due to the level of eccentriccontrol required during step descent.

This chapter is not intended to advocate for a particular surgical technique, but it does provide insight into improving our understanding of the pathophysiology of anterior knee pain syndrome. Our objectives were: to identify a relationship, or lack of one, between the presence of PFM and the presence of anterior knee pain; to analyze the long-term response of VMO muscle fibers to increased resting length; and to determine the incidence of patellofemoral osteoarthritis after IPR surgery. Our findings indicate (1) that not all PFM knees show symptoms; that is, PFM is not a sufficient condition for the onset of symptoms, at least in postoperative patients; (2) that the advancement of VMO has no deleterious effects on VMO; and (3) that IPR does not predispose to retropatellar osteoarthritis.

There is no substitute for a thorough history and a complete and careful physical examination. The history and physical examination still remain the first step for making an accurate diagnosis of anterior knee pain and patellar instability above any technique of diagnostic image. Imaging studies are a second step and can never replace the former. Surgical indications should not be based only on methods of image diagnosis as there is a poor correlation between clinical and image data. Finally, arthroscopy should be used judiciously and no realignment surgery should be based solely on the arthroscopic analysis of the patellofemoral congruence.