Current Rehabilitation Principles Following Meniscus Repairs

Abstract

Purpose of review

The purpose of this review is to synthesize current science on meniscus anatomy and biomechanics and repair techniques to create an empirical foundation for postoperative rehabilitation precautions and guidelines, including timelines, clinical and performance-based criteria for return to activity, to maximize both meniscal healing potential and patient recovery.

Recent Findings

Recent literature has focused on meniscus repair rather than debridement, and rehabilitation protocols should be designed to optimize healing. Complex, unstable tears, like root and radial tears, disrupt hoop stress and warrant a more conservative protocol including 6 weeks of non-weightbearing; however, more stable tears, like ramp and vertical tears, can often weight bear immediately after surgery. All protocols should emphasize early protected joint motion. Return to activity guidelines remain ill-defined but this review explores evidence-based recommendations for timelines, strength and performance testing. Patients typically should wait ≥ 4 months for a return to activity and the presence of joint line tenderness or effusion could be a sign of delayed/failed healing.

Summary

It is essential for therapists to know the size, type, and location of a meniscus repair to optimize patient outcomes. Guidelines for weight bearing, range of motion, strength training, and return to activity should vary per tear type and repair technique and recovery should be both time- and criteria-based. Return to activity should align with healing time, objective clinical and performance testing, and clinical and imaging exam findings. Future research should aim to optimize repair techniques and rehabilitation protocols, specifically further study on the timing to initiate weightbearing, early motion, and return to activity.

Graphical Abstract

Clinical and physical performance testing criteria for return to run, jump and sport

Introduction

The menisci contribute to joint nutrition and lubrication, joint stability, joint proprioception, and shock absorption. Quantitative anatomy studies have defined the meniscal root and capsular attachments of both menisci and meniscus repairs should strive to reproduce this normal anatomy [1–4]. Meniscus tears are the most common intra-articular injury at the knee, with 850,000 meniscus surgeries performed annually, and may occur secondary to trauma or degeneration [5, 6]. Tearing of the meniscus impacts its capability to perform the more mechanical aspects of its function and alters joint homeostasis on a biological level [7]. Some meniscal tears have the capacity to heal; however, meniscus pathology and deficiency is associated with a higher incidence of knee osteoarthritis (OA) [5, 6]. A meniscectomy in symptomatic patients may create short term symptom relief; however, meniscectomy is associated with a faster progression of OA and higher rates of total knee arthroplasty (TKA) compared to surgical repair or even leaving the tear in-situ [8]. Meniscus repair is therefore attempted more often in recent decades to restore the function of the menisci and ideally preserve long term joint health. A failed meniscus repair results in a fivefold increase in post-traumatic knee OA (PTOA) [9]. A consensus is lacking on best practices for postoperative rehabilitation protocols to maximize the likelihood of repair healing. Specifically, evidence-based guidelines for immediate post-operative precautions, timelines and criteria for return to activity and sport are ill-defined. The purpose of this review is to explore meniscus anatomy and function in the context of meniscus tears, review surgical techniques for repair, and highlight critical considerations for postoperative rehabilitation to maximize meniscal protection and healing potential while safely advancing patients back to an active lifestyle.

Meniscus Function and Biology

Different collagen fiber types are found within the layers of the meniscus, contributing to its functions related to joint stability and load management. The circumferential fibers, located in the deepest layer of the meniscus, help convert axial loading into hoop stress to manage joint compression [10]. Tearing of these fibers with radial and root tears (Fig. 1and Fig. 2) can disrupt the load management capacity of the menisci. Radial collagen (tie) fibers are found in the more superficial layer of the meniscus and weave among the circumferential fibers, providing a crucial role in resisting separation of the circumferential bundles [10]. Vertical longitudinal tears (Fig. 3) disrupt these fibers while leaving the circumferential fibers largely intact.

Fig. 1.

Arthroscopic image of a radial tear of the medial meniscus in a left knee

Fig. 2.

Arthroscopic image of a posterior medial meniscus root tear in a right knee

Fig. 3.

Arthroscopic image of a vertical, longitudinal tear of the lateral meniscus in a right knee

In addition to disruption of mechanical function, tearing of the meniscus elicits a biological response within the joint that varies by tear type and location [7]. The synovial fluid shows evidence of an inflammatory response, and an altered biological environment may persist for months after injury [7]. Although the meniscus is nourished partly through its blood supply, it largely achieves nutrition through synovial fluid permeating through joint movement and cyclical compression with weight bearing [11]. Cyclical loading is helpful for promoting meniscal healing, through both mechanical and biological stimuli. Proinflammatory mediators are reduced within the joint and anabolism increases in response to cyclical loading at certain levels; however, “safe levels” of joint loading are not clearly defined [7]. Static loading at high levels has been found to break down the extra-cellular matrix (ECM), which would be counterproductive to meniscal healing [7].

Additional factors may influence meniscal loading, and potentially healing, after repair. Varus limb alignment contributes to elevated loads through the medial compartment and has been found to be associated with increased failure rates following medial meniscus repair [12, 13]. Body mass index (BMI) was not found to influence healing rates following meniscus repair in a cohort of 305 patients comparing increased (> 25) to normal (< 25) BMI [14]. However, elevated BMI has been identified as a risk factor for both failure and poorer outcomes after posterior medial meniscus root repair [15, 16].

Meniscus Tear Patterns and Repair Techniques

Meniscal Tear Patterns

A vertical meniscus tear (Fig. 3) courses from the top to the bottom of the meniscus most commonly along the peripheral edges. Repairs of this type of tear have a better chance of healing if they are near the meniscus periphery (red-red zone). A radial tear (Fig. 1) is oriented perpendicular to the circumferential fibers of the meniscus and can partially or completely disrupt the meniscus collagen fibers. Full thickness radial tears are more ominous because they can completely destabilize the hoop stress ability of the meniscus. A meniscus root tear (Fig. 2) is either a detachment of the meniscus from the bony tibial attachment or a radial or complex tear within 1 cm of this root attachment [17]. This tear type has a less favorable prognosis because it can create joint conditions equivalent to a subtotal meniscectomy as the meniscus loses its ability to cushion the joint and often extrudes out of the joint [18]. Another common tear type is a horizontal cleavage tear (Fig. 4), which exhibits a separation between the upper and lower halves of the meniscus. If the upper or lower leaflets of the meniscus are resected with this tear type it removes a significant portion of the shock absorbing capacity of the meniscus [19, 20]. Other tear variants include radial flap tears or complex macerated tears which may be unrepairable and require resection of the torn portion of the meniscus, which is called a partial meniscectomy.

Fig. 4.

Arthroscopic image of a horizontal cleavage tear of the medial meniscus in a left knee

Repair Techniques

The four basic meniscus repair techniques primarily utilized are all-inside, inside-out, outside-in, and transtibial repairs. The most common is the all-inside technique, whereby sutures are used to repair a meniscus tear using an all-inside suture insertion device. These are useful for smaller tears or tears closer to the periphery of the meniscus. A drawback to this technique is that there are larger diameter needle holes, so one has to ensure that the meniscus substance is able to tolerate suture placement without risk of causing the hole in the meniscus to propagate. For the inside-out repair, an incision is made either along the medial or lateral aspect of the knee and double loaded needles with sutures are placed from inside the joint and are retrieved outside of the joint and then tied over the joint capsule. This is a more technically difficult procedure and usually requires a skilled assistant to safely retrieve the sutures. However, the holes made with the needles are smaller and more sutures can be placed in more difficult locations. The outside-in technique, used mostly for anterior horn meniscal tears, uses hollow needles placed from outside the joint into the meniscus tissue. Sutures are shuttled through the needles and captured through a snare placed in a second adjacent needle and pulled back through the meniscus and tied over the anterior joint capsule. The transtibial tunnel technique uses a small cannula that is drilled through the tibia into the location of the desired repair (commonly performed with two adjacent cannulas). Self-capture sutures are placed into the meniscus close to the tear location and then shuttled down the cannula, with the sutures tied over a button on the anterior tibia. This technique is most often used for meniscus root and radial repairs.

It is important to assess the healing environment for the meniscus. With most meniscus tears, rasping the tear will help stimulate further healing. When a meniscus repair is performed concurrent with an ACL reconstruction, it is well recognized that the release of marrow agents as part of the reaming of the tunnels for the ACL reconstruction increases the ability of the meniscus to heal [21, 22]. For isolated meniscus repairs, performing a marrow venting procedure has been reported to increase the ability of the meniscus to heal [23]. A marrow venting procedure utilizes a microfracture awl to make holes in the lateral aspect of the intercondylar notch to release bone marrow products. These bone marrow products are felt to include anabolic agents which can help with meniscus healing [22]. In effect, it is trying to create a positive healing environment similar to that seen with tunnel reaming observed with an ACL reconstruction.

Red-Red, Red-White, White-White Tears

The distance from the edge of the meniscocapsular junction to the location of the tear is generally classified based upon the relative blood supply to the meniscus and hence its ability to heal with a repair. In general, a tear within 3 mm of the rim is considered a red-red tear, one 3–6 mm from the periphery is a red-white tear and tears > 6 mm inside the joint are while-white zone repairs. The red-red zone tears have the best blood supply and have the highest ability for a repair to heal.

Post-Operative Rehabilitation

Physical therapy following meniscus repair should aim to protect and preserve the repair through appropriate precautions, while minimizing the negative consequences of reduced physical activity and joint and limb disuse associated with those precautions. The degree of protection required postoperatively may vary based on the tear type, tear location, the type of repair performed, and any concomitant procedures. Additional consideration may be given to patient age, BMI, limb alignment, and underlying joint health. Physical therapy should progress in a gradual, criteria-based fashion, while adhering to timelines and symptom/joint reactivity, to guide patients back to their preferred lifestyle (Table 1).

Flow Diagram 1. Clinical and physical performance testing criteria for return to run, jump and sport

Table 1.

Phase by phase post-operative progressions

Phase I | “Recovery” | 0–6 weeks
Precautions	• WB restriction o Radial/Root/Horizontal Cleavage: NWB o Vertical Longitudinal/Ramp: WBAT • ROM: 90-degree restriction × 2 weeks • Brace at 0 deg (removed for exercise)
Priorities	• Interventions for pain and swelling control (compression, ice, activity modification, elevation, manual interventions) • Joint nutrition, ROM activities (advancing per precautions) • Quadriceps muscle reactivation (NMES, BFR) o Exercise selection with reduced tibial shear (fixed angle isometrics, SLR, resisted TKE) (Fig. 5) • Safe maintenance of strength at other muscle groups • Well-limb/upper body cardiovascular fitness
Criteria for advancement	• Effusion 2 + or less • ROM: Full extension, 120 degrees knee flexion • Quadriceps: Strong volitional contraction, able to perform SLR with no extensor lag × 20 + repetitions
Phase II | “Transition” | 6–9 weeks
• Transition off crutches with gait: focus on restoring healthy gait pattern with gradual increases in walking speed and duration • Establish initial joint tolerance for load: Introduce/progress WB (body weight) exercises o Observe for no reactive effusion or increased joint soreness persisting > 24 h after activity
Phase III | “Rebuild” | 9–16 + weeks
Precautions	• Limit WB knee flexion depth to ≤ 70 degrees × 16 weeks (squat/step/lunge activities) • Root/Radial: Avoid aggressive, resisted hamstring curling × 16 weeks
Priorities	• Restore full knee ROM (gradual with flexion) • Increase external load with exercise to stimulate muscle strength gains • Introduce balance and stability training with progressive challenge (incorporate visual, vestibular and cognitive loading) • Build cardiovascular fitness with low impact training options (bike, elliptical, swim)
Criteria for advancement	• Full knee ROM • Effusion 1 + or less consistently • Quad function: PkTq/BW ≥ 60%, LSI ≥ 65–70% • YBT(A) Squat: ≤ 8 cm side-to-side difference (SSD) • Tolerant of resistance training program o Observe for no reactive effusion or increased joint soreness persisting > 24 h after activity
Phase IV | “Restore” | 16–36 + weeks
Precautions	• Ongoing observations for new or increased 1) joint line tenderness, 2) knee effusion, 3) baseline joint soreness, 4) subjective report of catching/locking symptoms • Gradual introduction of higher demand tasks (deeper squatting, directional movement, impact) • Conduct a collaborative “risk to benefit analysis” based on patient’s pre-surgical level of function, joint health, tear/repair type for re-introducing/progressing to higher demand activities
Priorities	• Progressive jog/run program per sport demands (see FLOW DIAGRAM 1) • Develop top-end muscle strength • Plyometric (jump) training progressions (see FLOW DIAGRAM 1) • Progressive speed, RTD training with targeted strength work • Gradual introduction of sport-specific training elements: o Direction-change o Acceleration, deceleration and jumping o Sprinting o Sport-specific movements o Contact, distraction, intensity • Consider group-based training program for supervised training interactions with other athletes, sport-specific simulations • Supervised return to practice & competition activities per guidelines and tolerance (see FLOW DIAGRAM 1)

Abbreviations: (BFR) blood flow restriction, (NMES) neuromuscular electrical stimulation, (NWB) non-weight-bearing, (ROM) range of motion, (RTD) rate of torque development, (SLR) straight leg raise, (TKE) terminal knee extension, (WB) weight bearing, (WBAT) weight-bearing as tolerated

Considerations for Post-Operative Precautions and Rehabilitation

Joint Range of Motion (ROM)

The medial and lateral menisci exhibit different mobility and stability trends, largely dictated by the differing bony congruency of each compartment and varying degrees of meniscal fixation to the tibia, capsule and adjacent soft tissue structures. (Table 2) Both menisci translate to accommodate the rolling and gliding of the femoral condyles with knee range of motion (ROM). The menisci translate anteriorly with knee extension and posteriorly with knee flexion, with the lateral meniscus exhibiting greater mobility. (Table 2) The meniscal roots, in addition to the various meniscocapsular ligaments, serve as stabilizing anchors. This stability is compromised with injury to any of these structures and the meniscus may sublux and cause joint locking with knee motion. The posterior meniscal horns experience more load with deeper knee flexion angles and the anterior horns with end range extension [24]. Lin et al. demonstrated that vertical longitudinal tears at the posteromedial medial meniscus experienced compression in both the torn state and the repaired state with a progression into deeper knee flexion angles (90° to 135°) [25]. A similar finding of compression with deeper knee flexion was observed with experimental mid-body vertical longitudinal tears in a porcine model [26].

Table 2.

Structural and biomechanical considerations by compartment

	Medial Compartment	Lateral Compartment
Bony congruency	• Concave tibial plateau on convex femoral condyle • More structurally congruent • Broader articular cartilage contact zone	• Flat/convex tibial plateau on convex femoral condyle • Less structurally congruent • Smaller articular cartilage contact zone
Meniscal coverage of tibial plateau (% of total surface area)	51% to 74% [82–84]	75% to 93% [82–84]
% Axial load transmitted by meniscus at 0° and 90°	50% at 0°/85% at 90° [49, 50]	70% at 0°/70% at 90° [49, 50]
Meniscal attachment to tibial plateau	• Meniscotibial ligaments • Meniscofemoral ligaments (connect the posterior horn of the MM to the femur)	• Meniscotibial ligaments
Meniscal attachment to contractile tissue	Semimembranosus arm attachment posteromedially	Popliteomeniscal fascicles (connecting posterior aspect of lateral meniscus to popliteus tendon)
General meniscal mobility	Lesser meniscal excursion with knee motion	Increased meniscal excursion with knee motion
Meniscal translation with knee ROM	Knee extension: 5.1 mm anterior translation Knee flexion: 2.0 mm posterior translation [24]	Knee extension: 11.2 mm anterior translation Knee flexion: 10.0 mm posterior translation [24]
Meniscus root load to failure	Anterior: 655.5 N Posterior: 513.8 N [85, 86]	Anterior: 652.8 N Posterior: 509.0 N [85, 86]

Abbreviations: (LM) lateral meniscus, (mm) millimeters, (MM) medial meniscus, (N) Newtons

Early ROM is beneficial for joint health if it can be safely performed. (Table 1) Animal studies have reported both reduced meniscal collagen content and overall meniscal tissue atrophy with immobilization [27, 28]. Conversely, mobilization resulted in increased collagen content levels, comparable to that of the uninjured controls, and improved meniscal healing following an experimental medial meniscus vascular zone vertical longitudinal tear repair [27]. In the context of posterior medial meniscus root tears; however, an MRI study revealed increased posterior meniscal extrusion with deeper knee flexion (90°) compared to the intact state [29]. DePhillipo et al. conducted intra-operative examination of meniscus repairs in patients undergoing 2-stage surgeries with an initial tunnel bone grafting for revision ACLR [30]. The meniscus repair was performed at stage 1 and confirmation of healing/failure of the repair was performed at the stage 2 procedure. All patients were allowed to perform immediate ROM with a 90° limit for the first 2-weeks and then gradually progress toward full ROM. The overall healing rate was 86%, with 82.3% of root tears showing healing and 92.4% of peripheral meniscal tears showing healing with early motion allowed, even in the presence of an ACL-deficient knee [30]. A systematic review and meta-analysis by Schweizer et al. reported similar failure rates between patient cohorts following varied ROM precautions and timelines, with the immobilized knees showing the highest failure rate [31]. Further research is warranted to best define appropriate ROM guidelines by tear type.

Open Chain Quadriceps and Hamstring Muscle Strengthening

Restoring quadriceps muscle strength is critical for maximizing knee joint health following meniscus repairs. Deficits in quadriceps strength are reported to be associated with a progression of knee OA [32]. Greater quadriceps strength following meniscus root repair was reported to be associated with less meniscal extrusion, which is critical, because extrusion is a primary predictor of an accelerated OA progression [33, 34]. Open chain strengthening is beneficial to isolate individual muscle groups, and such exercises are the primary means of training during an early period of restricted WB after a meniscus repair. During the first 4 to 6 weeks after surgery, employing quadriceps exercises that minimize joint shear may be advisable to minimize tension through the repair. Isolated, resisted quadriceps strengthening creates anterior shear, most notably in the final degrees of knee extension from 40° to 0 $_{}^{\circ }$ [35–37]. Shear-avoidant exercises would include isometric contractions (initially in full extension and then at fixed angles of flexion), straight leg raises, and band-resisted contractions into terminal knee extension (TKE). (Fig. 5) Therapeutic interventions that amplify contractile intensity and override arthrogenic muscular inhibition (AMI) associated with post-operative pain and swelling are beneficial during this early window. Specifically, neuromuscular electrical stimulation (NMES) and blood flow restriction therapy (BFR) help maximize outcomes with strength training and minimize muscular atrophy [38]. Applying focal cooling (Fig. 5a) and transcutaneous electrical stimulation (TENS) to the knee joint during quadriceps muscle exercise can minimize AMI [39, 40].

Fig. 5.

Early Quadriceps Training Options

Similar training principles can be applied to hamstring strengthening. Isolated hamstring strengthening (ex: hamstring curls) into knee flexion induces posterior tibial shear, most notably as the knee flexes beyond 30° [35–37]. Shear-avoidant early exercises can include fixed angle isometrics and modified hip-hinging drills for proximal hamstring engagement, such as a supine straight legged bridge (legs over a ball or bench). (Fig. 6) When the repair involves the posterior horn of the medial meniscus, additional concern with hamstring training may arise related to the unique anatomy of the posteromedial knee. The direct arm of the semimembranosus attaches to the extra-articular zone of the posteromedial joint capsule [3]. The posterior horn of the medial meniscus has a broad zone of intra-articular attachment to the joint capsule in this same region. Delaying resisted hamstring curling exercises may be advised; however, biomechanical studies validating this concern do not exist and the precaution is primarily speculative based on the known anatomy of this region of the knee.

Fig. 6.

Early Hamstring Training Options

Joint Loading: Implications for Post-Operative WB and Squat Training

The appropriate amount, volume, and type of loading to promote meniscal healing without cascading into tissue overload and failure after a meniscus repair is not known. Studies investigating the combination of mechanical stimuli and the biological joint environment indicate that dynamic mechanical loading modulates the inflammatory response within the joint, contributing to greater anabolic pathways for healing and reduced catabolic enzymes that may contribute to tissue degradation and repair failure [41].

Meniscal hoop stress has been reported to be non-uniform in distribution and changes with the knee flexion angle [42]. Longitudinal tears (Fig. 3) in parallel with the circumferential fibers primarily disrupt the radially oriented collagen tie fibers, so hoop stress remains intact. With longitudinal tears, axial loading, with the knee in or near full extension, has been observed to compress together the meniscal tissue on either side of the tear, stabilizing it [42, 43]. For this reason, early WB with gait is often allowed after surgery, typically with the knee locked in extension with a brace. Conversely, radial meniscal tears (Fig. 1) sever the circumferential fibers, which significantly disrupts hoop stress, especially with complete tears (> 50%). Axial loading has been reported to create more stress at the apex of a radial tear, leading to tear propagation, potential meniscal extrusion, and separation of the opposing sides of the radial tear. These observations contribute to recommendations for patients being non-weight bearing (NWB) immediately following radial tear repairs. (Table 1) Biomechanical cadaver studies investigating axial WB load simulation on posterior meniscus root repairs show signs of increased suture loading and repair loosening, which justify an initial period of NWB after a root repair [44, 45]. Longer longitudinal and radial tears have been reported to exhibit higher concentrations of stress across the sides of the tear with loading and have lower healing rates reported after their repair [42, 46]. Intra-operative observations of greater tear length may warrant protected WB immediately after surgery, regardless of the meniscal tear pattern.

The menisci are loaded differently at deeper angles of knee flexion in weight bearing, as with squatting, stair climbing, or lunging. Becker et al. investigated meniscofemoral pressure with a progression of knee ROM under axial load [47]. They observed increasing pressure with deeper knee flexion with peak pressure noted at the posterior horns at 90°. Their testing did not include angles greater than 90° [47]. Deeper squatting is associated with increased knee joint compressive forces, increased posterior tibial shear, and greater load management demand at the meniscus [47–51]. For these reasons, the introduction of squatting should be delayed and progression into deeper squatting should occur gradually to allow the healing meniscus the capacity to accommodate to progressive loading. (Table 1) Squatting deeper than 60–70° is associated with increased posterior tibial shear, so this depth restriction is recommended for the first 3–4-months after any unstable meniscal repair surgery [36, 52–54].

Return to Activity Guidelines

Clinical Criteria

Return to activity and sport guidelines are ill-defined following meniscus repair. Time from surgery is the most cited criteria for clearing patients to return to sport (RTS), followed by knee ROM [55]. Neither of these criteria examine the physical or psychological readiness for sporting demands. Willinger et al. prospectively investigated meniscal healing status, per both clinical exam and MRI diagnostic criteria, at various time points following meniscus repair among athletes returning to sport [56]. Although 100% of the athletes returned to play by 6-months after surgery, only 45% were at their pre-injury level of play and evidence of meniscal healing was noted in only 56% of the athletes per MRI observations and 64% per clinical exam criteria at that time point [56]. The authors found that joint line tenderness and effusion were signs of delayed or prolonged healing. Joint line tenderness, as a clinical diagnostic tool, was also investigated in a recent systematic review and subgroup meta-analysis by Schoenecker et al. investigating clinical and imaging diagnostic criteria associated with meniscal repair healing status [57]. Their findings revealed that a lack of joint line tenderness on clinical exam was correlated with a healed meniscus repair observed on MRI and second look arthroscopy [57].

Strength and Physical Performance Testing Criteria

Evidence-based rehabilitation guidelines for returning to run, jump and sport specific to isolated meniscus repair are sparse [58]. Physical therapists often draw from protocols for the ACLR population when assessing readiness to advance into higher demand tasks. FLOW DIAGRAM 1 defines criteria used within our center for return to run, jump, and sport based upon ACLR research. Quadriceps muscle performance has been investigated in relation to running biomechanics following an ACLR. Differences in knee flexion excursion (KFE), or movement into slight knee flexion during the stance phase of running, can be used to identify insufficient shock absorption at the surgical limb [59, 60]. This moment is largely controlled by the quadriceps muscles. Knurr et al. identified that side-to-side limb symmetry of quadriceps rate of torque development (RTD) was more strongly associated with knee biomechanics, specifically between limb difference in peak KFE, with running compared to a limb symmetry index (LSI) comparison of peak torque [61]. Other studies have investigated quadriceps performance outcomes and established cut-off values associated with successfully returning to running after ACLR, with or without a meniscal procedure. These studies did not correlate their findings with an analysis of running biomechanics. Reported quadriceps strength cut-off criteria for individuals exhibiting a successful return to run from these studies were peak torque relative to body weight (PkTq/BW) of 1.45 to 1.60 Nm/kg and an LSI of 65% [62, 63].

Returning to jumping and sport requires a higher level of contractile force and speed than running and appropriate cut-off values for quadriceps muscle strength have been investigated. Graham et al. investigated deficits in knee joint power, compared to power contributions from the ankle and hip joints, with jumping following ACLR [64]. The authors identified a cut-off value of 2.07 Nm/kg (approximately 70% PkTq/BW) for relative quadriceps strength as a predictor of healthier power contributions from the knee joint with jumping tasks. Kuenze et al. established a cut-off of 3.0 Nm/kg (approximately 100% PkTq/BW) for relative quadriceps strength to safely return to high level activity [65].

Asymmetries with single limb squatting, as measured with the Y-balance test (YBT), have shown association with an increased risk of non-contact injury and were found to discriminate between injured and uninjured Division I athletes [66, 67]. Patients recovering from meniscus repair have been found to perform well on hopping tests with respect to LSI (≥ 88% LSI) as early as 4-months after surgery [68] but outcomes for relative performance (hop distance compared to height or leg length), performance relative to pre-operative status or healthy norms, and hopping kinematics and kinetics are not well studied.

Known Outcomes Following Meniscus Repair

Average meniscus repair failure rates of 22.3% to 24.3% have been reported [69]. Among athletes, a pooled failure rate of 21% has been reported, with a lower failure rate (9%) among professional athletes. [70] Medial meniscus repairs are found to fail four times more often than lateral repairs. [71] Most failures occur within the first 2 years after surgery, but up to 1/3 occur after 2 years. [31] A review by Everhart et al. identified that a sedentary lifestyle, not age, was associated with patient reported outcome (PROM) scores. [72] Specifically, sedentary patients, not older ones, exhibited worse PROMs. Both groups had similar failure rates. A high rate of RTS at a pre-injury level of play (89%) has been reported among athletes. [70, 73] The timing of RTS after an isolated meniscal repair has been reported to range from 4.3 to 6.5 months; however, return to pre-injury level of play is reported to be delayed until 10 months. [70, 74]

Strength and physical performance outcomes are commonly reported for a meniscus repair in the context of a concomitant ACLR. Quadriceps muscle strength has not been found to be significantly lower among ACLR patients with a concomitant meniscus repair. [75, 76] Conversely, hamstring strength has been found to remain depressed following an ACLR with a meniscus repair compared to an isolated ACLR within a cohort of patients utilizing hamstring ACLR autografts. [77, 78] Few studies have examined strength outcomes following an isolated meniscus repair, but within those studies a persistent quadriceps strength deficit was not observed. [79, 80] A more recent scoping review identified only 4 out of the 20 included studies reported on clinical or performance testing criteria for RTS clearance following isolated meniscus repair. [58]

A lack of clear objective criteria combined with a vague reliance on time from surgery for return to activity counseling may contribute to inappropriate patient expectations following meniscus surgery. Pihl K et al. conducted a prospective cohort study investigating patient expectations for recovery and return to leisure activity after meniscus surgery, with more debridement than repair procedures performed. [81] Most patients (91%) expected to be fully recovered within 3-months, with 60% expecting full recovery within only 1 month. A higher proportion of older patients (> 55 y/o) expected a shorter recovery period. At 3-months postoperatively, only 45% of patients were satisfied with their recovery and 59% of patients reported that their level of participation in leisure and recreational activities did not meet their pre-operative expectations. Better adherence to objective clinical strength and physical performance data collection following surgery and more research sharing those outcomes with the medical community are needed to create a more realistic picture of recovery to share with patients of all activity levels.

Conclusion

Post-operative rehabilitation protocols should integrate basic science related to meniscus anatomy, biomechanics, and biology, while incorporating known variables related to tear type and repair technique to maximize recovery and minimize postoperative morbidity. This foundation of knowledge and the unique considerations of each specific meniscus repair type may warrant different post-operative precautions, especially related to weight bearing and specific exercise and activity progressions. Early protected range of motion should be emphasized to promote healing. Progressions with rehabilitation and return to activity should be gradual to allow for tissue adaptation and based on the specific meniscus tear and repair, time, objective and performance-testing outcomes, and clinical and imaging examination when warranted. Further research is warranted to define protocols and precautions that more specifically align with meniscal tear details and repair techniques.

Key References

• Meniscal root tears: a classification system based on tear morphology. LaPrade CM, James EW, Cram TR, Feagin JA, Engebretsen L, LaPrade RF. Am J Sports Med. 2015 Feb;43(2):363-9. doi: 10.1177/0363546514559684. Epub 2014 Dec 1.PMID: 25451789

  • This work defined the 5 different types of meniscal root tears which allows for a more accurate description of tear types and allows for more accurate comparisons of surgical treatments.
• Outcomes After Biologically Augmented Isolated Meniscal Repair With Marrow Venting Are Comparable With Those After Meniscal Repair With Concomitant Anterior Cruciate Ligament Reconstruction. Dean CS, Chahla J, Matheny LM, Mitchell JJ, LaPrade RF.Am J Sports Med. 2017 May;45(6):1341-1348. doi: 10.1177/0363546516686968. Epub 2017 Feb 1.PMID: 28298056

  • This work reported that the addition of a marrow venting procedure (MVP) to release marrow products into the knee joint for an isolated meniscus repair allows for the addition of biological marrow products to enhance meniscal repairs.
• Tibial meniscal dynamics using three-dimensional reconstruction of magnetic resonance images. Thompson WO, Thaete FL, Fu FH, Dye SF .Am J Sports Med. 1991 May-Jun;19(3):210-5; discussion 215-6. doi: 10.1177/036354659101900302.PMID: 1867329

  • This classic work defined the amount of medial and lateral meniscus motion with knee flexion and extension which assists with understanding the effects of meniscus injury and subsequent repairs.
• A Lack of Joint Line Tenderness Is Consistent With a Healed Meniscus, But Positive Clinical Examination Findings and MRI Scans Are Inconsistent in Identifying Failure After Meniscal Repair: A Systematic Review and Subgroup Meta-analysis. Schoenecker JH, Tollefson LV, Solaiman RH, Monson JK, Homan MD, Dornan GJ, Kennedy NI, Ronnblad E, LaPrade RF.Am J Sports Med. 2025 Jan 22:3635465241295709. doi: 10.1177/03635465241295709. Online ahead of print. PMID: 39841079

  • This systematic review reported that the most important clinical examination finding for the success of a meniscal repair was a lack of joit line tenderness based upon both postoperative MRI scans and second look arthroscopy.

Author Contribution

Concept/idea/research design: Jill Monson, Robert LaPrade, Luke Tollefson, Christopher LaPrade. Acquisition of data: NA. Analysis and interpretation of data: NA. Writing/review/editing of manuscript: Jill Monson, Robert LaPrade, Luke Tollefson, Christopher LaPrade. Preperation of Figures: Jill Monson and Luke Tollefson. Final approval of the manuscript: Jill Monson and Robert LaPrade.

Funding

No funding was received.

Data Availability

No datasets were generated or analysed during the current study.

Declarations

Human and Animal Rights and Informed Consent

All reported studies/experiments with human or animal subjects performed by the authors have been previously published and complied with all applicable ethical standards(including the Helsinki declaration and its amendments, institutional/national research committee standards, and international/national/institutional guidelines).

Conflict of Interest

Jill Monson, PT, OCS: Financial Disclosure and Conflict of Interest. —Consultant: Ossur, Smith & Nephew -Committees: AASPT Research Committee. Dr. Robert F. LaPrade, MD, PhD: Financial Disclosure and Conflict of Interest.—Consultant: Ossur, Smith & Nephew, Responsive Arthroscopy—Royalties: Ossur, Smith & Nephew, Elsevier, Arthrex—Research Grants: Ossur, Smith & Nephew, AANA, AOSSM—Committees: ISAKOS, AOSSM, AANA—Editorial Board: AJSM, JEO, KSSTA, JKS, JISPT, OTSM—Education: Foundation Medical. Luke Tollefson, BS: No Financial Disclosures and Conflict of Interest. Dr. Christopher M. LaPrade, MD: Financial Disclosure and Conflict of Interest. Educational support: Evolution Surgical, Inc, Foundation Medical, LLC, Arthrex, and Smith & Nephew. Speaker fees from DJO.